initial commit

drivers/gpu/drm/xen/Kconfig

@@ -0,0 +1,19 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config DRM_XEN
+	bool "DRM Support for Xen guest OS"
+	depends on XEN
+	help
+	  Choose this option if you want to enable DRM support
+	  for Xen.
+
+config DRM_XEN_FRONTEND
+	tristate "Para-virtualized frontend driver for Xen guest OS"
+	depends on DRM_XEN
+	depends on DRM
+	select DRM_KMS_HELPER
+	select VIDEOMODE_HELPERS
+	select XEN_XENBUS_FRONTEND
+	select XEN_FRONT_PGDIR_SHBUF
+	help
+	  Choose this option if you want to enable a para-virtualized
+	  frontend DRM/KMS driver for Xen guest OSes.

drivers/gpu/drm/xen/Makefile

@@ -0,0 +1,10 @@
+# SPDX-License-Identifier: GPL-2.0 OR MIT
+
+drm_xen_front-objs := xen_drm_front.o \
+		      xen_drm_front_kms.o \
+		      xen_drm_front_conn.o \
+		      xen_drm_front_evtchnl.o \
+		      xen_drm_front_cfg.o \
+		      xen_drm_front_gem.o
+
+obj-$(CONFIG_DRM_XEN_FRONTEND) += drm_xen_front.o

drivers/gpu/drm/xen/xen_drm_front.c

@@ -0,0 +1,818 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#include <linux/delay.h>
+#include <linux/dma-mapping.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_ioctl.h>
+#include <drm/drm_probe_helper.h>
+#include <drm/drm_file.h>
+#include <drm/drm_gem.h>
+
+#include <xen/platform_pci.h>
+#include <xen/xen.h>
+#include <xen/xenbus.h>
+
+#include <xen/xen-front-pgdir-shbuf.h>
+#include <xen/interface/io/displif.h>
+
+#include "xen_drm_front.h"
+#include "xen_drm_front_cfg.h"
+#include "xen_drm_front_evtchnl.h"
+#include "xen_drm_front_gem.h"
+#include "xen_drm_front_kms.h"
+
+struct xen_drm_front_dbuf {
+	struct list_head list;
+	u64 dbuf_cookie;
+	u64 fb_cookie;
+
+	struct xen_front_pgdir_shbuf shbuf;
+};
+
+static void dbuf_add_to_list(struct xen_drm_front_info *front_info,
+			     struct xen_drm_front_dbuf *dbuf, u64 dbuf_cookie)
+{
+	dbuf->dbuf_cookie = dbuf_cookie;
+	list_add(&dbuf->list, &front_info->dbuf_list);
+}
+
+static struct xen_drm_front_dbuf *dbuf_get(struct list_head *dbuf_list,
+					   u64 dbuf_cookie)
+{
+	struct xen_drm_front_dbuf *buf, *q;
+
+	list_for_each_entry_safe(buf, q, dbuf_list, list)
+		if (buf->dbuf_cookie == dbuf_cookie)
+			return buf;
+
+	return NULL;
+}
+
+static void dbuf_free(struct list_head *dbuf_list, u64 dbuf_cookie)
+{
+	struct xen_drm_front_dbuf *buf, *q;
+
+	list_for_each_entry_safe(buf, q, dbuf_list, list)
+		if (buf->dbuf_cookie == dbuf_cookie) {
+			list_del(&buf->list);
+			xen_front_pgdir_shbuf_unmap(&buf->shbuf);
+			xen_front_pgdir_shbuf_free(&buf->shbuf);
+			kfree(buf);
+			break;
+		}
+}
+
+static void dbuf_free_all(struct list_head *dbuf_list)
+{
+	struct xen_drm_front_dbuf *buf, *q;
+
+	list_for_each_entry_safe(buf, q, dbuf_list, list) {
+		list_del(&buf->list);
+		xen_front_pgdir_shbuf_unmap(&buf->shbuf);
+		xen_front_pgdir_shbuf_free(&buf->shbuf);
+		kfree(buf);
+	}
+}
+
+static struct xendispl_req *
+be_prepare_req(struct xen_drm_front_evtchnl *evtchnl, u8 operation)
+{
+	struct xendispl_req *req;
+
+	req = RING_GET_REQUEST(&evtchnl->u.req.ring,
+			       evtchnl->u.req.ring.req_prod_pvt);
+	req->operation = operation;
+	req->id = evtchnl->evt_next_id++;
+	evtchnl->evt_id = req->id;
+	return req;
+}
+
+static int be_stream_do_io(struct xen_drm_front_evtchnl *evtchnl,
+			   struct xendispl_req *req)
+{
+	reinit_completion(&evtchnl->u.req.completion);
+	if (unlikely(evtchnl->state != EVTCHNL_STATE_CONNECTED))
+		return -EIO;
+
+	xen_drm_front_evtchnl_flush(evtchnl);
+	return 0;
+}
+
+static int be_stream_wait_io(struct xen_drm_front_evtchnl *evtchnl)
+{
+	if (wait_for_completion_timeout(&evtchnl->u.req.completion,
+			msecs_to_jiffies(XEN_DRM_FRONT_WAIT_BACK_MS)) <= 0)
+		return -ETIMEDOUT;
+
+	return evtchnl->u.req.resp_status;
+}
+
+int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline *pipeline,
+			   u32 x, u32 y, u32 width, u32 height,
+			   u32 bpp, u64 fb_cookie)
+{
+	struct xen_drm_front_evtchnl *evtchnl;
+	struct xen_drm_front_info *front_info;
+	struct xendispl_req *req;
+	unsigned long flags;
+	int ret;
+
+	front_info = pipeline->drm_info->front_info;
+	evtchnl = &front_info->evt_pairs[pipeline->index].req;
+	if (unlikely(!evtchnl))
+		return -EIO;
+
+	mutex_lock(&evtchnl->u.req.req_io_lock);
+
+	spin_lock_irqsave(&front_info->io_lock, flags);
+	req = be_prepare_req(evtchnl, XENDISPL_OP_SET_CONFIG);
+	req->op.set_config.x = x;
+	req->op.set_config.y = y;
+	req->op.set_config.width = width;
+	req->op.set_config.height = height;
+	req->op.set_config.bpp = bpp;
+	req->op.set_config.fb_cookie = fb_cookie;
+
+	ret = be_stream_do_io(evtchnl, req);
+	spin_unlock_irqrestore(&front_info->io_lock, flags);
+
+	if (ret == 0)
+		ret = be_stream_wait_io(evtchnl);
+
+	mutex_unlock(&evtchnl->u.req.req_io_lock);
+	return ret;
+}
+
+int xen_drm_front_dbuf_create(struct xen_drm_front_info *front_info,
+			      u64 dbuf_cookie, u32 width, u32 height,
+			      u32 bpp, u64 size, u32 offset,
+			      struct page **pages)
+{
+	struct xen_drm_front_evtchnl *evtchnl;
+	struct xen_drm_front_dbuf *dbuf;
+	struct xendispl_req *req;
+	struct xen_front_pgdir_shbuf_cfg buf_cfg;
+	unsigned long flags;
+	int ret;
+
+	evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
+	if (unlikely(!evtchnl))
+		return -EIO;
+
+	dbuf = kzalloc(sizeof(*dbuf), GFP_KERNEL);
+	if (!dbuf)
+		return -ENOMEM;
+
+	dbuf_add_to_list(front_info, dbuf, dbuf_cookie);
+
+	memset(&buf_cfg, 0, sizeof(buf_cfg));
+	buf_cfg.xb_dev = front_info->xb_dev;
+	buf_cfg.num_pages = DIV_ROUND_UP(size, PAGE_SIZE);
+	buf_cfg.pages = pages;
+	buf_cfg.pgdir = &dbuf->shbuf;
+	buf_cfg.be_alloc = front_info->cfg.be_alloc;
+
+	ret = xen_front_pgdir_shbuf_alloc(&buf_cfg);
+	if (ret < 0)
+		goto fail_shbuf_alloc;
+
+	mutex_lock(&evtchnl->u.req.req_io_lock);
+
+	spin_lock_irqsave(&front_info->io_lock, flags);
+	req = be_prepare_req(evtchnl, XENDISPL_OP_DBUF_CREATE);
+	req->op.dbuf_create.gref_directory =
+			xen_front_pgdir_shbuf_get_dir_start(&dbuf->shbuf);
+	req->op.dbuf_create.buffer_sz = size;
+	req->op.dbuf_create.data_ofs = offset;
+	req->op.dbuf_create.dbuf_cookie = dbuf_cookie;
+	req->op.dbuf_create.width = width;
+	req->op.dbuf_create.height = height;
+	req->op.dbuf_create.bpp = bpp;
+	if (buf_cfg.be_alloc)
+		req->op.dbuf_create.flags |= XENDISPL_DBUF_FLG_REQ_ALLOC;
+
+	ret = be_stream_do_io(evtchnl, req);
+	spin_unlock_irqrestore(&front_info->io_lock, flags);
+
+	if (ret < 0)
+		goto fail;
+
+	ret = be_stream_wait_io(evtchnl);
+	if (ret < 0)
+		goto fail;
+
+	ret = xen_front_pgdir_shbuf_map(&dbuf->shbuf);
+	if (ret < 0)
+		goto fail;
+
+	mutex_unlock(&evtchnl->u.req.req_io_lock);
+	return 0;
+
+fail:
+	mutex_unlock(&evtchnl->u.req.req_io_lock);
+fail_shbuf_alloc:
+	dbuf_free(&front_info->dbuf_list, dbuf_cookie);
+	return ret;
+}
+
+static int xen_drm_front_dbuf_destroy(struct xen_drm_front_info *front_info,
+				      u64 dbuf_cookie)
+{
+	struct xen_drm_front_evtchnl *evtchnl;
+	struct xendispl_req *req;
+	unsigned long flags;
+	bool be_alloc;
+	int ret;
+
+	evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
+	if (unlikely(!evtchnl))
+		return -EIO;
+
+	be_alloc = front_info->cfg.be_alloc;
+
+	/*
+	 * For the backend allocated buffer release references now, so backend
+	 * can free the buffer.
+	 */
+	if (be_alloc)
+		dbuf_free(&front_info->dbuf_list, dbuf_cookie);
+
+	mutex_lock(&evtchnl->u.req.req_io_lock);
+
+	spin_lock_irqsave(&front_info->io_lock, flags);
+	req = be_prepare_req(evtchnl, XENDISPL_OP_DBUF_DESTROY);
+	req->op.dbuf_destroy.dbuf_cookie = dbuf_cookie;
+
+	ret = be_stream_do_io(evtchnl, req);
+	spin_unlock_irqrestore(&front_info->io_lock, flags);
+
+	if (ret == 0)
+		ret = be_stream_wait_io(evtchnl);
+
+	/*
+	 * Do this regardless of communication status with the backend:
+	 * if we cannot remove remote resources remove what we can locally.
+	 */
+	if (!be_alloc)
+		dbuf_free(&front_info->dbuf_list, dbuf_cookie);
+
+	mutex_unlock(&evtchnl->u.req.req_io_lock);
+	return ret;
+}
+
+int xen_drm_front_fb_attach(struct xen_drm_front_info *front_info,
+			    u64 dbuf_cookie, u64 fb_cookie, u32 width,
+			    u32 height, u32 pixel_format)
+{
+	struct xen_drm_front_evtchnl *evtchnl;
+	struct xen_drm_front_dbuf *buf;
+	struct xendispl_req *req;
+	unsigned long flags;
+	int ret;
+
+	evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
+	if (unlikely(!evtchnl))
+		return -EIO;
+
+	buf = dbuf_get(&front_info->dbuf_list, dbuf_cookie);
+	if (!buf)
+		return -EINVAL;
+
+	buf->fb_cookie = fb_cookie;
+
+	mutex_lock(&evtchnl->u.req.req_io_lock);
+
+	spin_lock_irqsave(&front_info->io_lock, flags);
+	req = be_prepare_req(evtchnl, XENDISPL_OP_FB_ATTACH);
+	req->op.fb_attach.dbuf_cookie = dbuf_cookie;
+	req->op.fb_attach.fb_cookie = fb_cookie;
+	req->op.fb_attach.width = width;
+	req->op.fb_attach.height = height;
+	req->op.fb_attach.pixel_format = pixel_format;
+
+	ret = be_stream_do_io(evtchnl, req);
+	spin_unlock_irqrestore(&front_info->io_lock, flags);
+
+	if (ret == 0)
+		ret = be_stream_wait_io(evtchnl);
+
+	mutex_unlock(&evtchnl->u.req.req_io_lock);
+	return ret;
+}
+
+int xen_drm_front_fb_detach(struct xen_drm_front_info *front_info,
+			    u64 fb_cookie)
+{
+	struct xen_drm_front_evtchnl *evtchnl;
+	struct xendispl_req *req;
+	unsigned long flags;
+	int ret;
+
+	evtchnl = &front_info->evt_pairs[GENERIC_OP_EVT_CHNL].req;
+	if (unlikely(!evtchnl))
+		return -EIO;
+
+	mutex_lock(&evtchnl->u.req.req_io_lock);
+
+	spin_lock_irqsave(&front_info->io_lock, flags);
+	req = be_prepare_req(evtchnl, XENDISPL_OP_FB_DETACH);
+	req->op.fb_detach.fb_cookie = fb_cookie;
+
+	ret = be_stream_do_io(evtchnl, req);
+	spin_unlock_irqrestore(&front_info->io_lock, flags);
+
+	if (ret == 0)
+		ret = be_stream_wait_io(evtchnl);
+
+	mutex_unlock(&evtchnl->u.req.req_io_lock);
+	return ret;
+}
+
+int xen_drm_front_page_flip(struct xen_drm_front_info *front_info,
+			    int conn_idx, u64 fb_cookie)
+{
+	struct xen_drm_front_evtchnl *evtchnl;
+	struct xendispl_req *req;
+	unsigned long flags;
+	int ret;
+
+	if (unlikely(conn_idx >= front_info->num_evt_pairs))
+		return -EINVAL;
+
+	evtchnl = &front_info->evt_pairs[conn_idx].req;
+
+	mutex_lock(&evtchnl->u.req.req_io_lock);
+
+	spin_lock_irqsave(&front_info->io_lock, flags);
+	req = be_prepare_req(evtchnl, XENDISPL_OP_PG_FLIP);
+	req->op.pg_flip.fb_cookie = fb_cookie;
+
+	ret = be_stream_do_io(evtchnl, req);
+	spin_unlock_irqrestore(&front_info->io_lock, flags);
+
+	if (ret == 0)
+		ret = be_stream_wait_io(evtchnl);
+
+	mutex_unlock(&evtchnl->u.req.req_io_lock);
+	return ret;
+}
+
+void xen_drm_front_on_frame_done(struct xen_drm_front_info *front_info,
+				 int conn_idx, u64 fb_cookie)
+{
+	struct xen_drm_front_drm_info *drm_info = front_info->drm_info;
+
+	if (unlikely(conn_idx >= front_info->cfg.num_connectors))
+		return;
+
+	xen_drm_front_kms_on_frame_done(&drm_info->pipeline[conn_idx],
+					fb_cookie);
+}
+
+static int xen_drm_drv_dumb_create(struct drm_file *filp,
+				   struct drm_device *dev,
+				   struct drm_mode_create_dumb *args)
+{
+	struct xen_drm_front_drm_info *drm_info = dev->dev_private;
+	struct drm_gem_object *obj;
+	int ret;
+
+	/*
+	 * Dumb creation is a two stage process: first we create a fully
+	 * constructed GEM object which is communicated to the backend, and
+	 * only after that we can create GEM's handle. This is done so,
+	 * because of the possible races: once you create a handle it becomes
+	 * immediately visible to user-space, so the latter can try accessing
+	 * object without pages etc.
+	 * For details also see drm_gem_handle_create
+	 */
+	args->pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
+	args->size = args->pitch * args->height;
+
+	obj = xen_drm_front_gem_create(dev, args->size);
+	if (IS_ERR(obj)) {
+		ret = PTR_ERR(obj);
+		goto fail;
+	}
+
+	ret = xen_drm_front_dbuf_create(drm_info->front_info,
+					xen_drm_front_dbuf_to_cookie(obj),
+					args->width, args->height, args->bpp,
+					args->size, 0,
+					xen_drm_front_gem_get_pages(obj));
+	if (ret)
+		goto fail_backend;
+
+	/* This is the tail of GEM object creation */
+	ret = drm_gem_handle_create(filp, obj, &args->handle);
+	if (ret)
+		goto fail_handle;
+
+	/* Drop reference from allocate - handle holds it now */
+	drm_gem_object_put(obj);
+	return 0;
+
+fail_handle:
+	xen_drm_front_dbuf_destroy(drm_info->front_info,
+				   xen_drm_front_dbuf_to_cookie(obj));
+fail_backend:
+	/* drop reference from allocate */
+	drm_gem_object_put(obj);
+fail:
+	DRM_ERROR("Failed to create dumb buffer: %d\n", ret);
+	return ret;
+}
+
+static void xen_drm_drv_free_object_unlocked(struct drm_gem_object *obj)
+{
+	struct xen_drm_front_drm_info *drm_info = obj->dev->dev_private;
+	int idx;
+
+	if (drm_dev_enter(obj->dev, &idx)) {
+		xen_drm_front_dbuf_destroy(drm_info->front_info,
+					   xen_drm_front_dbuf_to_cookie(obj));
+		drm_dev_exit(idx);
+	} else {
+		dbuf_free(&drm_info->front_info->dbuf_list,
+			  xen_drm_front_dbuf_to_cookie(obj));
+	}
+
+	xen_drm_front_gem_free_object_unlocked(obj);
+}
+
+static void xen_drm_drv_release(struct drm_device *dev)
+{
+	struct xen_drm_front_drm_info *drm_info = dev->dev_private;
+	struct xen_drm_front_info *front_info = drm_info->front_info;
+
+	xen_drm_front_kms_fini(drm_info);
+
+	drm_atomic_helper_shutdown(dev);
+	drm_mode_config_cleanup(dev);
+
+	if (front_info->cfg.be_alloc)
+		xenbus_switch_state(front_info->xb_dev,
+				    XenbusStateInitialising);
+
+	kfree(drm_info);
+}
+
+static const struct file_operations xen_drm_dev_fops = {
+	.owner          = THIS_MODULE,
+	.open           = drm_open,
+	.release        = drm_release,
+	.unlocked_ioctl = drm_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl   = drm_compat_ioctl,
+#endif
+	.poll           = drm_poll,
+	.read           = drm_read,
+	.llseek         = no_llseek,
+	.mmap           = xen_drm_front_gem_mmap,
+};
+
+static const struct vm_operations_struct xen_drm_drv_vm_ops = {
+	.open           = drm_gem_vm_open,
+	.close          = drm_gem_vm_close,
+};
+
+static struct drm_driver xen_drm_driver = {
+	.driver_features           = DRIVER_GEM | DRIVER_MODESET | DRIVER_ATOMIC,
+	.release                   = xen_drm_drv_release,
+	.gem_vm_ops                = &xen_drm_drv_vm_ops,
+	.gem_free_object_unlocked  = xen_drm_drv_free_object_unlocked,
+	.prime_handle_to_fd        = drm_gem_prime_handle_to_fd,
+	.prime_fd_to_handle        = drm_gem_prime_fd_to_handle,
+	.gem_prime_import_sg_table = xen_drm_front_gem_import_sg_table,
+	.gem_prime_get_sg_table    = xen_drm_front_gem_get_sg_table,
+	.gem_prime_vmap            = xen_drm_front_gem_prime_vmap,
+	.gem_prime_vunmap          = xen_drm_front_gem_prime_vunmap,
+	.gem_prime_mmap            = xen_drm_front_gem_prime_mmap,
+	.dumb_create               = xen_drm_drv_dumb_create,
+	.fops                      = &xen_drm_dev_fops,
+	.name                      = "xendrm-du",
+	.desc                      = "Xen PV DRM Display Unit",
+	.date                      = "20180221",
+	.major                     = 1,
+	.minor                     = 0,
+
+};
+
+static int xen_drm_drv_init(struct xen_drm_front_info *front_info)
+{
+	struct device *dev = &front_info->xb_dev->dev;
+	struct xen_drm_front_drm_info *drm_info;
+	struct drm_device *drm_dev;
+	int ret;
+
+	DRM_INFO("Creating %s\n", xen_drm_driver.desc);
+
+	drm_info = kzalloc(sizeof(*drm_info), GFP_KERNEL);
+	if (!drm_info) {
+		ret = -ENOMEM;
+		goto fail;
+	}
+
+	drm_info->front_info = front_info;
+	front_info->drm_info = drm_info;
+
+	drm_dev = drm_dev_alloc(&xen_drm_driver, dev);
+	if (IS_ERR(drm_dev)) {
+		ret = PTR_ERR(drm_dev);
+		goto fail_dev;
+	}
+
+	drm_info->drm_dev = drm_dev;
+
+	drm_dev->dev_private = drm_info;
+
+	ret = xen_drm_front_kms_init(drm_info);
+	if (ret) {
+		DRM_ERROR("Failed to initialize DRM/KMS, ret %d\n", ret);
+		goto fail_modeset;
+	}
+
+	ret = drm_dev_register(drm_dev, 0);
+	if (ret)
+		goto fail_register;
+
+	DRM_INFO("Initialized %s %d.%d.%d %s on minor %d\n",
+		 xen_drm_driver.name, xen_drm_driver.major,
+		 xen_drm_driver.minor, xen_drm_driver.patchlevel,
+		 xen_drm_driver.date, drm_dev->primary->index);
+
+	return 0;
+
+fail_register:
+	drm_dev_unregister(drm_dev);
+fail_modeset:
+	drm_kms_helper_poll_fini(drm_dev);
+	drm_mode_config_cleanup(drm_dev);
+	drm_dev_put(drm_dev);
+fail_dev:
+	kfree(drm_info);
+	front_info->drm_info = NULL;
+fail:
+	return ret;
+}
+
+static void xen_drm_drv_fini(struct xen_drm_front_info *front_info)
+{
+	struct xen_drm_front_drm_info *drm_info = front_info->drm_info;
+	struct drm_device *dev;
+
+	if (!drm_info)
+		return;
+
+	dev = drm_info->drm_dev;
+	if (!dev)
+		return;
+
+	/* Nothing to do if device is already unplugged */
+	if (drm_dev_is_unplugged(dev))
+		return;
+
+	drm_kms_helper_poll_fini(dev);
+	drm_dev_unplug(dev);
+	drm_dev_put(dev);
+
+	front_info->drm_info = NULL;
+
+	xen_drm_front_evtchnl_free_all(front_info);
+	dbuf_free_all(&front_info->dbuf_list);
+
+	/*
+	 * If we are not using backend allocated buffers, then tell the
+	 * backend we are ready to (re)initialize. Otherwise, wait for
+	 * drm_driver.release.
+	 */
+	if (!front_info->cfg.be_alloc)
+		xenbus_switch_state(front_info->xb_dev,
+				    XenbusStateInitialising);
+}
+
+static int displback_initwait(struct xen_drm_front_info *front_info)
+{
+	struct xen_drm_front_cfg *cfg = &front_info->cfg;
+	int ret;
+
+	cfg->front_info = front_info;
+	ret = xen_drm_front_cfg_card(front_info, cfg);
+	if (ret < 0)
+		return ret;
+
+	DRM_INFO("Have %d connector(s)\n", cfg->num_connectors);
+	/* Create event channels for all connectors and publish */
+	ret = xen_drm_front_evtchnl_create_all(front_info);
+	if (ret < 0)
+		return ret;
+
+	return xen_drm_front_evtchnl_publish_all(front_info);
+}
+
+static int displback_connect(struct xen_drm_front_info *front_info)
+{
+	xen_drm_front_evtchnl_set_state(front_info, EVTCHNL_STATE_CONNECTED);
+	return xen_drm_drv_init(front_info);
+}
+
+static void displback_disconnect(struct xen_drm_front_info *front_info)
+{
+	if (!front_info->drm_info)
+		return;
+
+	/* Tell the backend to wait until we release the DRM driver. */
+	xenbus_switch_state(front_info->xb_dev, XenbusStateReconfiguring);
+
+	xen_drm_drv_fini(front_info);
+}
+
+static void displback_changed(struct xenbus_device *xb_dev,
+			      enum xenbus_state backend_state)
+{
+	struct xen_drm_front_info *front_info = dev_get_drvdata(&xb_dev->dev);
+	int ret;
+
+	DRM_DEBUG("Backend state is %s, front is %s\n",
+		  xenbus_strstate(backend_state),
+		  xenbus_strstate(xb_dev->state));
+
+	switch (backend_state) {
+	case XenbusStateReconfiguring:
+	case XenbusStateReconfigured:
+	case XenbusStateInitialised:
+		break;
+
+	case XenbusStateInitialising:
+		if (xb_dev->state == XenbusStateReconfiguring)
+			break;
+
+		/* recovering after backend unexpected closure */
+		displback_disconnect(front_info);
+		break;
+
+	case XenbusStateInitWait:
+		if (xb_dev->state == XenbusStateReconfiguring)
+			break;
+
+		/* recovering after backend unexpected closure */
+		displback_disconnect(front_info);
+		if (xb_dev->state != XenbusStateInitialising)
+			break;
+
+		ret = displback_initwait(front_info);
+		if (ret < 0)
+			xenbus_dev_fatal(xb_dev, ret, "initializing frontend");
+		else
+			xenbus_switch_state(xb_dev, XenbusStateInitialised);
+		break;
+
+	case XenbusStateConnected:
+		if (xb_dev->state != XenbusStateInitialised)
+			break;
+
+		ret = displback_connect(front_info);
+		if (ret < 0) {
+			displback_disconnect(front_info);
+			xenbus_dev_fatal(xb_dev, ret, "connecting backend");
+		} else {
+			xenbus_switch_state(xb_dev, XenbusStateConnected);
+		}
+		break;
+
+	case XenbusStateClosing:
+		/*
+		 * in this state backend starts freeing resources,
+		 * so let it go into closed state, so we can also
+		 * remove ours
+		 */
+		break;
+
+	case XenbusStateUnknown:
+	case XenbusStateClosed:
+		if (xb_dev->state == XenbusStateClosed)
+			break;
+
+		displback_disconnect(front_info);
+		break;
+	}
+}
+
+static int xen_drv_probe(struct xenbus_device *xb_dev,
+			 const struct xenbus_device_id *id)
+{
+	struct xen_drm_front_info *front_info;
+	struct device *dev = &xb_dev->dev;
+	int ret;
+
+	ret = dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(64));
+	if (ret < 0) {
+		DRM_ERROR("Cannot setup DMA mask, ret %d", ret);
+		return ret;
+	}
+
+	front_info = devm_kzalloc(&xb_dev->dev,
+				  sizeof(*front_info), GFP_KERNEL);
+	if (!front_info)
+		return -ENOMEM;
+
+	front_info->xb_dev = xb_dev;
+	spin_lock_init(&front_info->io_lock);
+	INIT_LIST_HEAD(&front_info->dbuf_list);
+	dev_set_drvdata(&xb_dev->dev, front_info);
+
+	return xenbus_switch_state(xb_dev, XenbusStateInitialising);
+}
+
+static int xen_drv_remove(struct xenbus_device *dev)
+{
+	struct xen_drm_front_info *front_info = dev_get_drvdata(&dev->dev);
+	int to = 100;
+
+	xenbus_switch_state(dev, XenbusStateClosing);
+
+	/*
+	 * On driver removal it is disconnected from XenBus,
+	 * so no backend state change events come via .otherend_changed
+	 * callback. This prevents us from exiting gracefully, e.g.
+	 * signaling the backend to free event channels, waiting for its
+	 * state to change to XenbusStateClosed and cleaning at our end.
+	 * Normally when front driver removed backend will finally go into
+	 * XenbusStateInitWait state.
+	 *
+	 * Workaround: read backend's state manually and wait with time-out.
+	 */
+	while ((xenbus_read_unsigned(front_info->xb_dev->otherend, "state",
+				     XenbusStateUnknown) != XenbusStateInitWait) &&
+				     --to)
+		msleep(10);
+
+	if (!to) {
+		unsigned int state;
+
+		state = xenbus_read_unsigned(front_info->xb_dev->otherend,
+					     "state", XenbusStateUnknown);
+		DRM_ERROR("Backend state is %s while removing driver\n",
+			  xenbus_strstate(state));
+	}
+
+	xen_drm_drv_fini(front_info);
+	xenbus_frontend_closed(dev);
+	return 0;
+}
+
+static const struct xenbus_device_id xen_driver_ids[] = {
+	{ XENDISPL_DRIVER_NAME },
+	{ "" }
+};
+
+static struct xenbus_driver xen_driver = {
+	.ids = xen_driver_ids,
+	.probe = xen_drv_probe,
+	.remove = xen_drv_remove,
+	.otherend_changed = displback_changed,
+};
+
+static int __init xen_drv_init(void)
+{
+	/* At the moment we only support case with XEN_PAGE_SIZE == PAGE_SIZE */
+	if (XEN_PAGE_SIZE != PAGE_SIZE) {
+		DRM_ERROR(XENDISPL_DRIVER_NAME ": different kernel and Xen page sizes are not supported: XEN_PAGE_SIZE (%lu) != PAGE_SIZE (%lu)\n",
+			  XEN_PAGE_SIZE, PAGE_SIZE);
+		return -ENODEV;
+	}
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	if (!xen_has_pv_devices())
+		return -ENODEV;
+
+	DRM_INFO("Registering XEN PV " XENDISPL_DRIVER_NAME "\n");
+	return xenbus_register_frontend(&xen_driver);
+}
+
+static void __exit xen_drv_fini(void)
+{
+	DRM_INFO("Unregistering XEN PV " XENDISPL_DRIVER_NAME "\n");
+	xenbus_unregister_driver(&xen_driver);
+}
+
+module_init(xen_drv_init);
+module_exit(xen_drv_fini);
+
+MODULE_DESCRIPTION("Xen para-virtualized display device frontend");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("xen:" XENDISPL_DRIVER_NAME);

drivers/gpu/drm/xen/xen_drm_front.h

@@ -0,0 +1,163 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#ifndef __XEN_DRM_FRONT_H_
+#define __XEN_DRM_FRONT_H_
+
+#include <linux/scatterlist.h>
+
+#include <drm/drm_connector.h>
+#include <drm/drm_simple_kms_helper.h>
+
+#include "xen_drm_front_cfg.h"
+
+struct drm_device;
+struct drm_framebuffer;
+struct drm_gem_object;
+struct drm_pending_vblank_event;
+
+/**
+ * DOC: Driver modes of operation in terms of display buffers used
+ *
+ * Depending on the requirements for the para-virtualized environment, namely
+ * requirements dictated by the accompanying DRM/(v)GPU drivers running in both
+ * host and guest environments, display buffers can be allocated by either
+ * frontend driver or backend.
+ */
+
+/**
+ * DOC: Buffers allocated by the frontend driver
+ *
+ * In this mode of operation driver allocates buffers from system memory.
+ *
+ * Note! If used with accompanying DRM/(v)GPU drivers this mode of operation
+ * may require IOMMU support on the platform, so accompanying DRM/vGPU
+ * hardware can still reach display buffer memory while importing PRIME
+ * buffers from the frontend driver.
+ */
+
+/**
+ * DOC: Buffers allocated by the backend
+ *
+ * This mode of operation is run-time configured via guest domain configuration
+ * through XenStore entries.
+ *
+ * For systems which do not provide IOMMU support, but having specific
+ * requirements for display buffers it is possible to allocate such buffers
+ * at backend side and share those with the frontend.
+ * For example, if host domain is 1:1 mapped and has DRM/GPU hardware expecting
+ * physically contiguous memory, this allows implementing zero-copying
+ * use-cases.
+ *
+ * Note, while using this scenario the following should be considered:
+ *
+ * #. If guest domain dies then pages/grants received from the backend
+ *    cannot be claimed back
+ *
+ * #. Misbehaving guest may send too many requests to the
+ *    backend exhausting its grant references and memory
+ *    (consider this from security POV)
+ */
+
+/**
+ * DOC: Driver limitations
+ *
+ * #. Only primary plane without additional properties is supported.
+ *
+ * #. Only one video mode per connector supported which is configured
+ *    via XenStore.
+ *
+ * #. All CRTCs operate at fixed frequency of 60Hz.
+ */
+
+/* timeout in ms to wait for backend to respond */
+#define XEN_DRM_FRONT_WAIT_BACK_MS	3000
+
+#ifndef GRANT_INVALID_REF
+/*
+ * Note on usage of grant reference 0 as invalid grant reference:
+ * grant reference 0 is valid, but never exposed to a PV driver,
+ * because of the fact it is already in use/reserved by the PV console.
+ */
+#define GRANT_INVALID_REF	0
+#endif
+
+struct xen_drm_front_info {
+	struct xenbus_device *xb_dev;
+	struct xen_drm_front_drm_info *drm_info;
+
+	/* to protect data between backend IO code and interrupt handler */
+	spinlock_t io_lock;
+
+	int num_evt_pairs;
+	struct xen_drm_front_evtchnl_pair *evt_pairs;
+	struct xen_drm_front_cfg cfg;
+
+	/* display buffers */
+	struct list_head dbuf_list;
+};
+
+struct xen_drm_front_drm_pipeline {
+	struct xen_drm_front_drm_info *drm_info;
+
+	int index;
+
+	struct drm_simple_display_pipe pipe;
+
+	struct drm_connector conn;
+	/* These are only for connector mode checking */
+	int width, height;
+
+	struct drm_pending_vblank_event *pending_event;
+
+	struct delayed_work pflip_to_worker;
+
+	bool conn_connected;
+};
+
+struct xen_drm_front_drm_info {
+	struct xen_drm_front_info *front_info;
+	struct drm_device *drm_dev;
+
+	struct xen_drm_front_drm_pipeline pipeline[XEN_DRM_FRONT_MAX_CRTCS];
+};
+
+static inline u64 xen_drm_front_fb_to_cookie(struct drm_framebuffer *fb)
+{
+	return (uintptr_t)fb;
+}
+
+static inline u64 xen_drm_front_dbuf_to_cookie(struct drm_gem_object *gem_obj)
+{
+	return (uintptr_t)gem_obj;
+}
+
+int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline *pipeline,
+			   u32 x, u32 y, u32 width, u32 height,
+			   u32 bpp, u64 fb_cookie);
+
+int xen_drm_front_dbuf_create(struct xen_drm_front_info *front_info,
+			      u64 dbuf_cookie, u32 width, u32 height,
+			      u32 bpp, u64 size, u32 offset, struct page **pages);
+
+int xen_drm_front_fb_attach(struct xen_drm_front_info *front_info,
+			    u64 dbuf_cookie, u64 fb_cookie, u32 width,
+			    u32 height, u32 pixel_format);
+
+int xen_drm_front_fb_detach(struct xen_drm_front_info *front_info,
+			    u64 fb_cookie);
+
+int xen_drm_front_page_flip(struct xen_drm_front_info *front_info,
+			    int conn_idx, u64 fb_cookie);
+
+void xen_drm_front_on_frame_done(struct xen_drm_front_info *front_info,
+				 int conn_idx, u64 fb_cookie);
+
+#endif /* __XEN_DRM_FRONT_H_ */

drivers/gpu/drm/xen/xen_drm_front_cfg.c

@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#include <linux/device.h>
+
+#include <drm/drm_print.h>
+
+#include <xen/interface/io/displif.h>
+#include <xen/xenbus.h>
+
+#include "xen_drm_front.h"
+#include "xen_drm_front_cfg.h"
+
+static int cfg_connector(struct xen_drm_front_info *front_info,
+			 struct xen_drm_front_cfg_connector *connector,
+			 const char *path, int index)
+{
+	char *connector_path;
+
+	connector_path = devm_kasprintf(&front_info->xb_dev->dev,
+					GFP_KERNEL, "%s/%d", path, index);
+	if (!connector_path)
+		return -ENOMEM;
+
+	if (xenbus_scanf(XBT_NIL, connector_path, XENDISPL_FIELD_RESOLUTION,
+			 "%d" XENDISPL_RESOLUTION_SEPARATOR "%d",
+			 &connector->width, &connector->height) < 0) {
+		/* either no entry configured or wrong resolution set */
+		connector->width = 0;
+		connector->height = 0;
+		return -EINVAL;
+	}
+
+	connector->xenstore_path = connector_path;
+
+	DRM_INFO("Connector %s: resolution %dx%d\n",
+		 connector_path, connector->width, connector->height);
+	return 0;
+}
+
+int xen_drm_front_cfg_card(struct xen_drm_front_info *front_info,
+			   struct xen_drm_front_cfg *cfg)
+{
+	struct xenbus_device *xb_dev = front_info->xb_dev;
+	int ret, i;
+
+	if (xenbus_read_unsigned(front_info->xb_dev->nodename,
+				 XENDISPL_FIELD_BE_ALLOC, 0)) {
+		DRM_INFO("Backend can provide display buffers\n");
+		cfg->be_alloc = true;
+	}
+
+	cfg->num_connectors = 0;
+	for (i = 0; i < ARRAY_SIZE(cfg->connectors); i++) {
+		ret = cfg_connector(front_info, &cfg->connectors[i],
+				    xb_dev->nodename, i);
+		if (ret < 0)
+			break;
+		cfg->num_connectors++;
+	}
+
+	if (!cfg->num_connectors) {
+		DRM_ERROR("No connector(s) configured at %s\n",
+			  xb_dev->nodename);
+		return -ENODEV;
+	}
+
+	return 0;
+}
+

drivers/gpu/drm/xen/xen_drm_front_cfg.h

@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#ifndef __XEN_DRM_FRONT_CFG_H_
+#define __XEN_DRM_FRONT_CFG_H_
+
+#include <linux/types.h>
+
+#define XEN_DRM_FRONT_MAX_CRTCS	4
+
+struct xen_drm_front_cfg_connector {
+	int width;
+	int height;
+	char *xenstore_path;
+};
+
+struct xen_drm_front_cfg {
+	struct xen_drm_front_info *front_info;
+	/* number of connectors in this configuration */
+	int num_connectors;
+	/* connector configurations */
+	struct xen_drm_front_cfg_connector connectors[XEN_DRM_FRONT_MAX_CRTCS];
+	/* set if dumb buffers are allocated externally on backend side */
+	bool be_alloc;
+};
+
+int xen_drm_front_cfg_card(struct xen_drm_front_info *front_info,
+			   struct xen_drm_front_cfg *cfg);
+
+#endif /* __XEN_DRM_FRONT_CFG_H_ */

drivers/gpu/drm/xen/xen_drm_front_conn.c

@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_probe_helper.h>
+
+#include <video/videomode.h>
+
+#include "xen_drm_front.h"
+#include "xen_drm_front_conn.h"
+#include "xen_drm_front_kms.h"
+
+static struct xen_drm_front_drm_pipeline *
+to_xen_drm_pipeline(struct drm_connector *connector)
+{
+	return container_of(connector, struct xen_drm_front_drm_pipeline, conn);
+}
+
+static const u32 plane_formats[] = {
+	DRM_FORMAT_RGB565,
+	DRM_FORMAT_RGB888,
+	DRM_FORMAT_XRGB8888,
+	DRM_FORMAT_ARGB8888,
+	DRM_FORMAT_XRGB4444,
+	DRM_FORMAT_ARGB4444,
+	DRM_FORMAT_XRGB1555,
+	DRM_FORMAT_ARGB1555,
+	DRM_FORMAT_YUYV,
+};
+
+const u32 *xen_drm_front_conn_get_formats(int *format_count)
+{
+	*format_count = ARRAY_SIZE(plane_formats);
+	return plane_formats;
+}
+
+static int connector_detect(struct drm_connector *connector,
+			    struct drm_modeset_acquire_ctx *ctx,
+			    bool force)
+{
+	struct xen_drm_front_drm_pipeline *pipeline =
+			to_xen_drm_pipeline(connector);
+
+	if (drm_dev_is_unplugged(connector->dev))
+		pipeline->conn_connected = false;
+
+	return pipeline->conn_connected ? connector_status_connected :
+			connector_status_disconnected;
+}
+
+#define XEN_DRM_CRTC_VREFRESH_HZ	60
+
+static int connector_get_modes(struct drm_connector *connector)
+{
+	struct xen_drm_front_drm_pipeline *pipeline =
+			to_xen_drm_pipeline(connector);
+	struct drm_display_mode *mode;
+	struct videomode videomode;
+	int width, height;
+
+	mode = drm_mode_create(connector->dev);
+	if (!mode)
+		return 0;
+
+	memset(&videomode, 0, sizeof(videomode));
+	videomode.hactive = pipeline->width;
+	videomode.vactive = pipeline->height;
+	width = videomode.hactive + videomode.hfront_porch +
+			videomode.hback_porch + videomode.hsync_len;
+	height = videomode.vactive + videomode.vfront_porch +
+			videomode.vback_porch + videomode.vsync_len;
+	videomode.pixelclock = width * height * XEN_DRM_CRTC_VREFRESH_HZ;
+	mode->type = DRM_MODE_TYPE_PREFERRED | DRM_MODE_TYPE_DRIVER;
+
+	drm_display_mode_from_videomode(&videomode, mode);
+	drm_mode_probed_add(connector, mode);
+	return 1;
+}
+
+static const struct drm_connector_helper_funcs connector_helper_funcs = {
+	.get_modes = connector_get_modes,
+	.detect_ctx = connector_detect,
+};
+
+static const struct drm_connector_funcs connector_funcs = {
+	.fill_modes = drm_helper_probe_single_connector_modes,
+	.destroy = drm_connector_cleanup,
+	.reset = drm_atomic_helper_connector_reset,
+	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
+	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
+};
+
+int xen_drm_front_conn_init(struct xen_drm_front_drm_info *drm_info,
+			    struct drm_connector *connector)
+{
+	struct xen_drm_front_drm_pipeline *pipeline =
+			to_xen_drm_pipeline(connector);
+
+	drm_connector_helper_add(connector, &connector_helper_funcs);
+
+	pipeline->conn_connected = true;
+
+	connector->polled = DRM_CONNECTOR_POLL_CONNECT |
+			DRM_CONNECTOR_POLL_DISCONNECT;
+
+	return drm_connector_init(drm_info->drm_dev, connector,
+				  &connector_funcs, DRM_MODE_CONNECTOR_VIRTUAL);
+}

drivers/gpu/drm/xen/xen_drm_front_conn.h

@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#ifndef __XEN_DRM_FRONT_CONN_H_
+#define __XEN_DRM_FRONT_CONN_H_
+
+#include <linux/types.h>
+
+struct drm_connector;
+struct xen_drm_front_drm_info;
+
+struct xen_drm_front_drm_info;
+
+int xen_drm_front_conn_init(struct xen_drm_front_drm_info *drm_info,
+			    struct drm_connector *connector);
+
+const u32 *xen_drm_front_conn_get_formats(int *format_count);
+
+#endif /* __XEN_DRM_FRONT_CONN_H_ */

drivers/gpu/drm/xen/xen_drm_front_evtchnl.c

@@ -0,0 +1,387 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#include <linux/errno.h>
+#include <linux/irq.h>
+
+#include <drm/drm_print.h>
+
+#include <xen/xenbus.h>
+#include <xen/events.h>
+#include <xen/grant_table.h>
+
+#include "xen_drm_front.h"
+#include "xen_drm_front_evtchnl.h"
+
+static irqreturn_t evtchnl_interrupt_ctrl(int irq, void *dev_id)
+{
+	struct xen_drm_front_evtchnl *evtchnl = dev_id;
+	struct xen_drm_front_info *front_info = evtchnl->front_info;
+	struct xendispl_resp *resp;
+	RING_IDX i, rp;
+	unsigned long flags;
+
+	if (unlikely(evtchnl->state != EVTCHNL_STATE_CONNECTED))
+		return IRQ_HANDLED;
+
+	spin_lock_irqsave(&front_info->io_lock, flags);
+
+again:
+	rp = evtchnl->u.req.ring.sring->rsp_prod;
+	/* ensure we see queued responses up to rp */
+	virt_rmb();
+
+	for (i = evtchnl->u.req.ring.rsp_cons; i != rp; i++) {
+		resp = RING_GET_RESPONSE(&evtchnl->u.req.ring, i);
+		if (unlikely(resp->id != evtchnl->evt_id))
+			continue;
+
+		switch (resp->operation) {
+		case XENDISPL_OP_PG_FLIP:
+		case XENDISPL_OP_FB_ATTACH:
+		case XENDISPL_OP_FB_DETACH:
+		case XENDISPL_OP_DBUF_CREATE:
+		case XENDISPL_OP_DBUF_DESTROY:
+		case XENDISPL_OP_SET_CONFIG:
+			evtchnl->u.req.resp_status = resp->status;
+			complete(&evtchnl->u.req.completion);
+			break;
+
+		default:
+			DRM_ERROR("Operation %d is not supported\n",
+				  resp->operation);
+			break;
+		}
+	}
+
+	evtchnl->u.req.ring.rsp_cons = i;
+
+	if (i != evtchnl->u.req.ring.req_prod_pvt) {
+		int more_to_do;
+
+		RING_FINAL_CHECK_FOR_RESPONSES(&evtchnl->u.req.ring,
+					       more_to_do);
+		if (more_to_do)
+			goto again;
+	} else {
+		evtchnl->u.req.ring.sring->rsp_event = i + 1;
+	}
+
+	spin_unlock_irqrestore(&front_info->io_lock, flags);
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t evtchnl_interrupt_evt(int irq, void *dev_id)
+{
+	struct xen_drm_front_evtchnl *evtchnl = dev_id;
+	struct xen_drm_front_info *front_info = evtchnl->front_info;
+	struct xendispl_event_page *page = evtchnl->u.evt.page;
+	u32 cons, prod;
+	unsigned long flags;
+
+	if (unlikely(evtchnl->state != EVTCHNL_STATE_CONNECTED))
+		return IRQ_HANDLED;
+
+	spin_lock_irqsave(&front_info->io_lock, flags);
+
+	prod = page->in_prod;
+	/* ensure we see ring contents up to prod */
+	virt_rmb();
+	if (prod == page->in_cons)
+		goto out;
+
+	for (cons = page->in_cons; cons != prod; cons++) {
+		struct xendispl_evt *event;
+
+		event = &XENDISPL_IN_RING_REF(page, cons);
+		if (unlikely(event->id != evtchnl->evt_id++))
+			continue;
+
+		switch (event->type) {
+		case XENDISPL_EVT_PG_FLIP:
+			xen_drm_front_on_frame_done(front_info, evtchnl->index,
+						    event->op.pg_flip.fb_cookie);
+			break;
+		}
+	}
+	page->in_cons = cons;
+	/* ensure ring contents */
+	virt_wmb();
+
+out:
+	spin_unlock_irqrestore(&front_info->io_lock, flags);
+	return IRQ_HANDLED;
+}
+
+static void evtchnl_free(struct xen_drm_front_info *front_info,
+			 struct xen_drm_front_evtchnl *evtchnl)
+{
+	unsigned long page = 0;
+
+	if (evtchnl->type == EVTCHNL_TYPE_REQ)
+		page = (unsigned long)evtchnl->u.req.ring.sring;
+	else if (evtchnl->type == EVTCHNL_TYPE_EVT)
+		page = (unsigned long)evtchnl->u.evt.page;
+	if (!page)
+		return;
+
+	evtchnl->state = EVTCHNL_STATE_DISCONNECTED;
+
+	if (evtchnl->type == EVTCHNL_TYPE_REQ) {
+		/* release all who still waits for response if any */
+		evtchnl->u.req.resp_status = -EIO;
+		complete_all(&evtchnl->u.req.completion);
+	}
+
+	if (evtchnl->irq)
+		unbind_from_irqhandler(evtchnl->irq, evtchnl);
+
+	if (evtchnl->port)
+		xenbus_free_evtchn(front_info->xb_dev, evtchnl->port);
+
+	/* end access and free the page */
+	if (evtchnl->gref != GRANT_INVALID_REF)
+		gnttab_end_foreign_access(evtchnl->gref, 0, page);
+
+	memset(evtchnl, 0, sizeof(*evtchnl));
+}
+
+static int evtchnl_alloc(struct xen_drm_front_info *front_info, int index,
+			 struct xen_drm_front_evtchnl *evtchnl,
+			 enum xen_drm_front_evtchnl_type type)
+{
+	struct xenbus_device *xb_dev = front_info->xb_dev;
+	unsigned long page;
+	grant_ref_t gref;
+	irq_handler_t handler;
+	int ret;
+
+	memset(evtchnl, 0, sizeof(*evtchnl));
+	evtchnl->type = type;
+	evtchnl->index = index;
+	evtchnl->front_info = front_info;
+	evtchnl->state = EVTCHNL_STATE_DISCONNECTED;
+	evtchnl->gref = GRANT_INVALID_REF;
+
+	page = get_zeroed_page(GFP_NOIO | __GFP_HIGH);
+	if (!page) {
+		ret = -ENOMEM;
+		goto fail;
+	}
+
+	if (type == EVTCHNL_TYPE_REQ) {
+		struct xen_displif_sring *sring;
+
+		init_completion(&evtchnl->u.req.completion);
+		mutex_init(&evtchnl->u.req.req_io_lock);
+		sring = (struct xen_displif_sring *)page;
+		SHARED_RING_INIT(sring);
+		FRONT_RING_INIT(&evtchnl->u.req.ring, sring, XEN_PAGE_SIZE);
+
+		ret = xenbus_grant_ring(xb_dev, sring, 1, &gref);
+		if (ret < 0) {
+			evtchnl->u.req.ring.sring = NULL;
+			free_page(page);
+			goto fail;
+		}
+
+		handler = evtchnl_interrupt_ctrl;
+	} else {
+		ret = gnttab_grant_foreign_access(xb_dev->otherend_id,
+						  virt_to_gfn((void *)page), 0);
+		if (ret < 0) {
+			free_page(page);
+			goto fail;
+		}
+
+		evtchnl->u.evt.page = (struct xendispl_event_page *)page;
+		gref = ret;
+		handler = evtchnl_interrupt_evt;
+	}
+	evtchnl->gref = gref;
+
+	ret = xenbus_alloc_evtchn(xb_dev, &evtchnl->port);
+	if (ret < 0)
+		goto fail;
+
+	ret = bind_evtchn_to_irqhandler(evtchnl->port,
+					handler, 0, xb_dev->devicetype,
+					evtchnl);
+	if (ret < 0)
+		goto fail;
+
+	evtchnl->irq = ret;
+	return 0;
+
+fail:
+	DRM_ERROR("Failed to allocate ring: %d\n", ret);
+	return ret;
+}
+
+int xen_drm_front_evtchnl_create_all(struct xen_drm_front_info *front_info)
+{
+	struct xen_drm_front_cfg *cfg;
+	int ret, conn;
+
+	cfg = &front_info->cfg;
+
+	front_info->evt_pairs =
+			kcalloc(cfg->num_connectors,
+				sizeof(struct xen_drm_front_evtchnl_pair),
+				GFP_KERNEL);
+	if (!front_info->evt_pairs) {
+		ret = -ENOMEM;
+		goto fail;
+	}
+
+	for (conn = 0; conn < cfg->num_connectors; conn++) {
+		ret = evtchnl_alloc(front_info, conn,
+				    &front_info->evt_pairs[conn].req,
+				    EVTCHNL_TYPE_REQ);
+		if (ret < 0) {
+			DRM_ERROR("Error allocating control channel\n");
+			goto fail;
+		}
+
+		ret = evtchnl_alloc(front_info, conn,
+				    &front_info->evt_pairs[conn].evt,
+				    EVTCHNL_TYPE_EVT);
+		if (ret < 0) {
+			DRM_ERROR("Error allocating in-event channel\n");
+			goto fail;
+		}
+	}
+	front_info->num_evt_pairs = cfg->num_connectors;
+	return 0;
+
+fail:
+	xen_drm_front_evtchnl_free_all(front_info);
+	return ret;
+}
+
+static int evtchnl_publish(struct xenbus_transaction xbt,
+			   struct xen_drm_front_evtchnl *evtchnl,
+			   const char *path, const char *node_ring,
+			   const char *node_chnl)
+{
+	struct xenbus_device *xb_dev = evtchnl->front_info->xb_dev;
+	int ret;
+
+	/* write control channel ring reference */
+	ret = xenbus_printf(xbt, path, node_ring, "%u", evtchnl->gref);
+	if (ret < 0) {
+		xenbus_dev_error(xb_dev, ret, "writing ring-ref");
+		return ret;
+	}
+
+	/* write event channel ring reference */
+	ret = xenbus_printf(xbt, path, node_chnl, "%u", evtchnl->port);
+	if (ret < 0) {
+		xenbus_dev_error(xb_dev, ret, "writing event channel");
+		return ret;
+	}
+
+	return 0;
+}
+
+int xen_drm_front_evtchnl_publish_all(struct xen_drm_front_info *front_info)
+{
+	struct xenbus_transaction xbt;
+	struct xen_drm_front_cfg *plat_data;
+	int ret, conn;
+
+	plat_data = &front_info->cfg;
+
+again:
+	ret = xenbus_transaction_start(&xbt);
+	if (ret < 0) {
+		xenbus_dev_fatal(front_info->xb_dev, ret,
+				 "starting transaction");
+		return ret;
+	}
+
+	for (conn = 0; conn < plat_data->num_connectors; conn++) {
+		ret = evtchnl_publish(xbt, &front_info->evt_pairs[conn].req,
+				      plat_data->connectors[conn].xenstore_path,
+				      XENDISPL_FIELD_REQ_RING_REF,
+				      XENDISPL_FIELD_REQ_CHANNEL);
+		if (ret < 0)
+			goto fail;
+
+		ret = evtchnl_publish(xbt, &front_info->evt_pairs[conn].evt,
+				      plat_data->connectors[conn].xenstore_path,
+				      XENDISPL_FIELD_EVT_RING_REF,
+				      XENDISPL_FIELD_EVT_CHANNEL);
+		if (ret < 0)
+			goto fail;
+	}
+
+	ret = xenbus_transaction_end(xbt, 0);
+	if (ret < 0) {
+		if (ret == -EAGAIN)
+			goto again;
+
+		xenbus_dev_fatal(front_info->xb_dev, ret,
+				 "completing transaction");
+		goto fail_to_end;
+	}
+
+	return 0;
+
+fail:
+	xenbus_transaction_end(xbt, 1);
+
+fail_to_end:
+	xenbus_dev_fatal(front_info->xb_dev, ret, "writing Xen store");
+	return ret;
+}
+
+void xen_drm_front_evtchnl_flush(struct xen_drm_front_evtchnl *evtchnl)
+{
+	int notify;
+
+	evtchnl->u.req.ring.req_prod_pvt++;
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&evtchnl->u.req.ring, notify);
+	if (notify)
+		notify_remote_via_irq(evtchnl->irq);
+}
+
+void xen_drm_front_evtchnl_set_state(struct xen_drm_front_info *front_info,
+				     enum xen_drm_front_evtchnl_state state)
+{
+	unsigned long flags;
+	int i;
+
+	if (!front_info->evt_pairs)
+		return;
+
+	spin_lock_irqsave(&front_info->io_lock, flags);
+	for (i = 0; i < front_info->num_evt_pairs; i++) {
+		front_info->evt_pairs[i].req.state = state;
+		front_info->evt_pairs[i].evt.state = state;
+	}
+	spin_unlock_irqrestore(&front_info->io_lock, flags);
+}
+
+void xen_drm_front_evtchnl_free_all(struct xen_drm_front_info *front_info)
+{
+	int i;
+
+	if (!front_info->evt_pairs)
+		return;
+
+	for (i = 0; i < front_info->num_evt_pairs; i++) {
+		evtchnl_free(front_info, &front_info->evt_pairs[i].req);
+		evtchnl_free(front_info, &front_info->evt_pairs[i].evt);
+	}
+
+	kfree(front_info->evt_pairs);
+	front_info->evt_pairs = NULL;
+}

drivers/gpu/drm/xen/xen_drm_front_evtchnl.h

@@ -0,0 +1,81 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#ifndef __XEN_DRM_FRONT_EVTCHNL_H_
+#define __XEN_DRM_FRONT_EVTCHNL_H_
+
+#include <linux/completion.h>
+#include <linux/types.h>
+
+#include <xen/interface/io/ring.h>
+#include <xen/interface/io/displif.h>
+
+/*
+ * All operations which are not connector oriented use this ctrl event channel,
+ * e.g. fb_attach/destroy which belong to a DRM device, not to a CRTC.
+ */
+#define GENERIC_OP_EVT_CHNL	0
+
+enum xen_drm_front_evtchnl_state {
+	EVTCHNL_STATE_DISCONNECTED,
+	EVTCHNL_STATE_CONNECTED,
+};
+
+enum xen_drm_front_evtchnl_type {
+	EVTCHNL_TYPE_REQ,
+	EVTCHNL_TYPE_EVT,
+};
+
+struct xen_drm_front_drm_info;
+
+struct xen_drm_front_evtchnl {
+	struct xen_drm_front_info *front_info;
+	int gref;
+	int port;
+	int irq;
+	int index;
+	enum xen_drm_front_evtchnl_state state;
+	enum xen_drm_front_evtchnl_type type;
+	/* either response id or incoming event id */
+	u16 evt_id;
+	/* next request id or next expected event id */
+	u16 evt_next_id;
+	union {
+		struct {
+			struct xen_displif_front_ring ring;
+			struct completion completion;
+			/* latest response status */
+			int resp_status;
+			/* serializer for backend IO: request/response */
+			struct mutex req_io_lock;
+		} req;
+		struct {
+			struct xendispl_event_page *page;
+		} evt;
+	} u;
+};
+
+struct xen_drm_front_evtchnl_pair {
+	struct xen_drm_front_evtchnl req;
+	struct xen_drm_front_evtchnl evt;
+};
+
+int xen_drm_front_evtchnl_create_all(struct xen_drm_front_info *front_info);
+
+int xen_drm_front_evtchnl_publish_all(struct xen_drm_front_info *front_info);
+
+void xen_drm_front_evtchnl_flush(struct xen_drm_front_evtchnl *evtchnl);
+
+void xen_drm_front_evtchnl_set_state(struct xen_drm_front_info *front_info,
+				     enum xen_drm_front_evtchnl_state state);
+
+void xen_drm_front_evtchnl_free_all(struct xen_drm_front_info *front_info);
+
+#endif /* __XEN_DRM_FRONT_EVTCHNL_H_ */

drivers/gpu/drm/xen/xen_drm_front_gem.c

@@ -0,0 +1,308 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#include <linux/dma-buf.h>
+#include <linux/scatterlist.h>
+#include <linux/shmem_fs.h>
+
+#include <drm/drm_fb_helper.h>
+#include <drm/drm_gem.h>
+#include <drm/drm_prime.h>
+#include <drm/drm_probe_helper.h>
+
+#include <xen/balloon.h>
+#include <xen/xen.h>
+
+#include "xen_drm_front.h"
+#include "xen_drm_front_gem.h"
+
+struct xen_gem_object {
+	struct drm_gem_object base;
+
+	size_t num_pages;
+	struct page **pages;
+
+	/* set for buffers allocated by the backend */
+	bool be_alloc;
+
+	/* this is for imported PRIME buffer */
+	struct sg_table *sgt_imported;
+};
+
+static inline struct xen_gem_object *
+to_xen_gem_obj(struct drm_gem_object *gem_obj)
+{
+	return container_of(gem_obj, struct xen_gem_object, base);
+}
+
+static int gem_alloc_pages_array(struct xen_gem_object *xen_obj,
+				 size_t buf_size)
+{
+	xen_obj->num_pages = DIV_ROUND_UP(buf_size, PAGE_SIZE);
+	xen_obj->pages = kvmalloc_array(xen_obj->num_pages,
+					sizeof(struct page *), GFP_KERNEL);
+	return !xen_obj->pages ? -ENOMEM : 0;
+}
+
+static void gem_free_pages_array(struct xen_gem_object *xen_obj)
+{
+	kvfree(xen_obj->pages);
+	xen_obj->pages = NULL;
+}
+
+static struct xen_gem_object *gem_create_obj(struct drm_device *dev,
+					     size_t size)
+{
+	struct xen_gem_object *xen_obj;
+	int ret;
+
+	xen_obj = kzalloc(sizeof(*xen_obj), GFP_KERNEL);
+	if (!xen_obj)
+		return ERR_PTR(-ENOMEM);
+
+	ret = drm_gem_object_init(dev, &xen_obj->base, size);
+	if (ret < 0) {
+		kfree(xen_obj);
+		return ERR_PTR(ret);
+	}
+
+	return xen_obj;
+}
+
+static struct xen_gem_object *gem_create(struct drm_device *dev, size_t size)
+{
+	struct xen_drm_front_drm_info *drm_info = dev->dev_private;
+	struct xen_gem_object *xen_obj;
+	int ret;
+
+	size = round_up(size, PAGE_SIZE);
+	xen_obj = gem_create_obj(dev, size);
+	if (IS_ERR(xen_obj))
+		return xen_obj;
+
+	if (drm_info->front_info->cfg.be_alloc) {
+		/*
+		 * backend will allocate space for this buffer, so
+		 * only allocate array of pointers to pages
+		 */
+		ret = gem_alloc_pages_array(xen_obj, size);
+		if (ret < 0)
+			goto fail;
+
+		/*
+		 * allocate ballooned pages which will be used to map
+		 * grant references provided by the backend
+		 */
+		ret = xen_alloc_unpopulated_pages(xen_obj->num_pages,
+					          xen_obj->pages);
+		if (ret < 0) {
+			DRM_ERROR("Cannot allocate %zu ballooned pages: %d\n",
+				  xen_obj->num_pages, ret);
+			gem_free_pages_array(xen_obj);
+			goto fail;
+		}
+
+		xen_obj->be_alloc = true;
+		return xen_obj;
+	}
+	/*
+	 * need to allocate backing pages now, so we can share those
+	 * with the backend
+	 */
+	xen_obj->num_pages = DIV_ROUND_UP(size, PAGE_SIZE);
+	xen_obj->pages = drm_gem_get_pages(&xen_obj->base);
+	if (IS_ERR(xen_obj->pages)) {
+		ret = PTR_ERR(xen_obj->pages);
+		xen_obj->pages = NULL;
+		goto fail;
+	}
+
+	return xen_obj;
+
+fail:
+	DRM_ERROR("Failed to allocate buffer with size %zu\n", size);
+	return ERR_PTR(ret);
+}
+
+struct drm_gem_object *xen_drm_front_gem_create(struct drm_device *dev,
+						size_t size)
+{
+	struct xen_gem_object *xen_obj;
+
+	xen_obj = gem_create(dev, size);
+	if (IS_ERR(xen_obj))
+		return ERR_CAST(xen_obj);
+
+	return &xen_obj->base;
+}
+
+void xen_drm_front_gem_free_object_unlocked(struct drm_gem_object *gem_obj)
+{
+	struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj);
+
+	if (xen_obj->base.import_attach) {
+		drm_prime_gem_destroy(&xen_obj->base, xen_obj->sgt_imported);
+		gem_free_pages_array(xen_obj);
+	} else {
+		if (xen_obj->pages) {
+			if (xen_obj->be_alloc) {
+				xen_free_unpopulated_pages(xen_obj->num_pages,
+							   xen_obj->pages);
+				gem_free_pages_array(xen_obj);
+			} else {
+				drm_gem_put_pages(&xen_obj->base,
+						  xen_obj->pages, true, false);
+			}
+		}
+	}
+	drm_gem_object_release(gem_obj);
+	kfree(xen_obj);
+}
+
+struct page **xen_drm_front_gem_get_pages(struct drm_gem_object *gem_obj)
+{
+	struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj);
+
+	return xen_obj->pages;
+}
+
+struct sg_table *xen_drm_front_gem_get_sg_table(struct drm_gem_object *gem_obj)
+{
+	struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj);
+
+	if (!xen_obj->pages)
+		return ERR_PTR(-ENOMEM);
+
+	return drm_prime_pages_to_sg(gem_obj->dev,
+				     xen_obj->pages, xen_obj->num_pages);
+}
+
+struct drm_gem_object *
+xen_drm_front_gem_import_sg_table(struct drm_device *dev,
+				  struct dma_buf_attachment *attach,
+				  struct sg_table *sgt)
+{
+	struct xen_drm_front_drm_info *drm_info = dev->dev_private;
+	struct xen_gem_object *xen_obj;
+	size_t size;
+	int ret;
+
+	size = attach->dmabuf->size;
+	xen_obj = gem_create_obj(dev, size);
+	if (IS_ERR(xen_obj))
+		return ERR_CAST(xen_obj);
+
+	ret = gem_alloc_pages_array(xen_obj, size);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	xen_obj->sgt_imported = sgt;
+
+	ret = drm_prime_sg_to_page_addr_arrays(sgt, xen_obj->pages,
+					       NULL, xen_obj->num_pages);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	ret = xen_drm_front_dbuf_create(drm_info->front_info,
+					xen_drm_front_dbuf_to_cookie(&xen_obj->base),
+					0, 0, 0, size, sgt->sgl->offset,
+					xen_obj->pages);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	DRM_DEBUG("Imported buffer of size %zu with nents %u\n",
+		  size, sgt->orig_nents);
+
+	return &xen_obj->base;
+}
+
+static int gem_mmap_obj(struct xen_gem_object *xen_obj,
+			struct vm_area_struct *vma)
+{
+	int ret;
+
+	/*
+	 * clear the VM_PFNMAP flag that was set by drm_gem_mmap(), and set the
+	 * vm_pgoff (used as a fake buffer offset by DRM) to 0 as we want to map
+	 * the whole buffer.
+	 */
+	vma->vm_flags &= ~VM_PFNMAP;
+	vma->vm_flags |= VM_MIXEDMAP;
+	vma->vm_pgoff = 0;
+	/*
+	 * According to Xen on ARM ABI (xen/include/public/arch-arm.h):
+	 * all memory which is shared with other entities in the system
+	 * (including the hypervisor and other guests) must reside in memory
+	 * which is mapped as Normal Inner Write-Back Outer Write-Back
+	 * Inner-Shareable.
+	 */
+	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
+
+	/*
+	 * vm_operations_struct.fault handler will be called if CPU access
+	 * to VM is here. For GPUs this isn't the case, because CPU
+	 * doesn't touch the memory. Insert pages now, so both CPU and GPU are
+	 * happy.
+	 * FIXME: as we insert all the pages now then no .fault handler must
+	 * be called, so don't provide one
+	 */
+	ret = vm_map_pages(vma, xen_obj->pages, xen_obj->num_pages);
+	if (ret < 0)
+		DRM_ERROR("Failed to map pages into vma: %d\n", ret);
+
+	return ret;
+}
+
+int xen_drm_front_gem_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	struct xen_gem_object *xen_obj;
+	struct drm_gem_object *gem_obj;
+	int ret;
+
+	ret = drm_gem_mmap(filp, vma);
+	if (ret < 0)
+		return ret;
+
+	gem_obj = vma->vm_private_data;
+	xen_obj = to_xen_gem_obj(gem_obj);
+	return gem_mmap_obj(xen_obj, vma);
+}
+
+void *xen_drm_front_gem_prime_vmap(struct drm_gem_object *gem_obj)
+{
+	struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj);
+
+	if (!xen_obj->pages)
+		return NULL;
+
+	/* Please see comment in gem_mmap_obj on mapping and attributes. */
+	return vmap(xen_obj->pages, xen_obj->num_pages,
+		    VM_MAP, PAGE_KERNEL);
+}
+
+void xen_drm_front_gem_prime_vunmap(struct drm_gem_object *gem_obj,
+				    void *vaddr)
+{
+	vunmap(vaddr);
+}
+
+int xen_drm_front_gem_prime_mmap(struct drm_gem_object *gem_obj,
+				 struct vm_area_struct *vma)
+{
+	struct xen_gem_object *xen_obj;
+	int ret;
+
+	ret = drm_gem_mmap_obj(gem_obj, gem_obj->size, vma);
+	if (ret < 0)
+		return ret;
+
+	xen_obj = to_xen_gem_obj(gem_obj);
+	return gem_mmap_obj(xen_obj, vma);
+}

drivers/gpu/drm/xen/xen_drm_front_gem.h

@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#ifndef __XEN_DRM_FRONT_GEM_H
+#define __XEN_DRM_FRONT_GEM_H
+
+struct dma_buf_attachment;
+struct drm_device;
+struct drm_gem_object;
+struct file;
+struct sg_table;
+struct vm_area_struct;
+
+struct drm_gem_object *xen_drm_front_gem_create(struct drm_device *dev,
+						size_t size);
+
+struct drm_gem_object *
+xen_drm_front_gem_import_sg_table(struct drm_device *dev,
+				  struct dma_buf_attachment *attach,
+				  struct sg_table *sgt);
+
+struct sg_table *xen_drm_front_gem_get_sg_table(struct drm_gem_object *gem_obj);
+
+struct page **xen_drm_front_gem_get_pages(struct drm_gem_object *obj);
+
+void xen_drm_front_gem_free_object_unlocked(struct drm_gem_object *gem_obj);
+
+int xen_drm_front_gem_mmap(struct file *filp, struct vm_area_struct *vma);
+
+void *xen_drm_front_gem_prime_vmap(struct drm_gem_object *gem_obj);
+
+void xen_drm_front_gem_prime_vunmap(struct drm_gem_object *gem_obj,
+				    void *vaddr);
+
+int xen_drm_front_gem_prime_mmap(struct drm_gem_object *gem_obj,
+				 struct vm_area_struct *vma);
+
+#endif /* __XEN_DRM_FRONT_GEM_H */

drivers/gpu/drm/xen/xen_drm_front_kms.c

@@ -0,0 +1,380 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#include <drm/drm_atomic.h>
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_gem.h>
+#include <drm/drm_gem_framebuffer_helper.h>
+#include <drm/drm_probe_helper.h>
+#include <drm/drm_vblank.h>
+
+#include "xen_drm_front.h"
+#include "xen_drm_front_conn.h"
+#include "xen_drm_front_kms.h"
+
+/*
+ * Timeout in ms to wait for frame done event from the backend:
+ * must be a bit more than IO time-out
+ */
+#define FRAME_DONE_TO_MS	(XEN_DRM_FRONT_WAIT_BACK_MS + 100)
+
+static struct xen_drm_front_drm_pipeline *
+to_xen_drm_pipeline(struct drm_simple_display_pipe *pipe)
+{
+	return container_of(pipe, struct xen_drm_front_drm_pipeline, pipe);
+}
+
+static void fb_destroy(struct drm_framebuffer *fb)
+{
+	struct xen_drm_front_drm_info *drm_info = fb->dev->dev_private;
+	int idx;
+
+	if (drm_dev_enter(fb->dev, &idx)) {
+		xen_drm_front_fb_detach(drm_info->front_info,
+					xen_drm_front_fb_to_cookie(fb));
+		drm_dev_exit(idx);
+	}
+	drm_gem_fb_destroy(fb);
+}
+
+static const struct drm_framebuffer_funcs fb_funcs = {
+	.destroy = fb_destroy,
+};
+
+static struct drm_framebuffer *
+fb_create(struct drm_device *dev, struct drm_file *filp,
+	  const struct drm_mode_fb_cmd2 *mode_cmd)
+{
+	struct xen_drm_front_drm_info *drm_info = dev->dev_private;
+	struct drm_framebuffer *fb;
+	struct drm_gem_object *gem_obj;
+	int ret;
+
+	fb = drm_gem_fb_create_with_funcs(dev, filp, mode_cmd, &fb_funcs);
+	if (IS_ERR(fb))
+		return fb;
+
+	gem_obj = fb->obj[0];
+
+	ret = xen_drm_front_fb_attach(drm_info->front_info,
+				      xen_drm_front_dbuf_to_cookie(gem_obj),
+				      xen_drm_front_fb_to_cookie(fb),
+				      fb->width, fb->height,
+				      fb->format->format);
+	if (ret < 0) {
+		DRM_ERROR("Back failed to attach FB %p: %d\n", fb, ret);
+		goto fail;
+	}
+
+	return fb;
+
+fail:
+	drm_gem_fb_destroy(fb);
+	return ERR_PTR(ret);
+}
+
+static const struct drm_mode_config_funcs mode_config_funcs = {
+	.fb_create = fb_create,
+	.atomic_check = drm_atomic_helper_check,
+	.atomic_commit = drm_atomic_helper_commit,
+};
+
+static void send_pending_event(struct xen_drm_front_drm_pipeline *pipeline)
+{
+	struct drm_crtc *crtc = &pipeline->pipe.crtc;
+	struct drm_device *dev = crtc->dev;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dev->event_lock, flags);
+	if (pipeline->pending_event)
+		drm_crtc_send_vblank_event(crtc, pipeline->pending_event);
+	pipeline->pending_event = NULL;
+	spin_unlock_irqrestore(&dev->event_lock, flags);
+}
+
+static void display_enable(struct drm_simple_display_pipe *pipe,
+			   struct drm_crtc_state *crtc_state,
+			   struct drm_plane_state *plane_state)
+{
+	struct xen_drm_front_drm_pipeline *pipeline =
+			to_xen_drm_pipeline(pipe);
+	struct drm_crtc *crtc = &pipe->crtc;
+	struct drm_framebuffer *fb = plane_state->fb;
+	int ret, idx;
+
+	if (!drm_dev_enter(pipe->crtc.dev, &idx))
+		return;
+
+	ret = xen_drm_front_mode_set(pipeline, crtc->x, crtc->y,
+				     fb->width, fb->height,
+				     fb->format->cpp[0] * 8,
+				     xen_drm_front_fb_to_cookie(fb));
+
+	if (ret) {
+		DRM_ERROR("Failed to enable display: %d\n", ret);
+		pipeline->conn_connected = false;
+	}
+
+	drm_dev_exit(idx);
+}
+
+static void display_disable(struct drm_simple_display_pipe *pipe)
+{
+	struct xen_drm_front_drm_pipeline *pipeline =
+			to_xen_drm_pipeline(pipe);
+	int ret = 0, idx;
+
+	if (drm_dev_enter(pipe->crtc.dev, &idx)) {
+		ret = xen_drm_front_mode_set(pipeline, 0, 0, 0, 0, 0,
+					     xen_drm_front_fb_to_cookie(NULL));
+		drm_dev_exit(idx);
+	}
+	if (ret)
+		DRM_ERROR("Failed to disable display: %d\n", ret);
+
+	/* Make sure we can restart with enabled connector next time */
+	pipeline->conn_connected = true;
+
+	/* release stalled event if any */
+	send_pending_event(pipeline);
+}
+
+void xen_drm_front_kms_on_frame_done(struct xen_drm_front_drm_pipeline *pipeline,
+				     u64 fb_cookie)
+{
+	/*
+	 * This runs in interrupt context, e.g. under
+	 * drm_info->front_info->io_lock, so we cannot call _sync version
+	 * to cancel the work
+	 */
+	cancel_delayed_work(&pipeline->pflip_to_worker);
+
+	send_pending_event(pipeline);
+}
+
+static void pflip_to_worker(struct work_struct *work)
+{
+	struct delayed_work *delayed_work = to_delayed_work(work);
+	struct xen_drm_front_drm_pipeline *pipeline =
+			container_of(delayed_work,
+				     struct xen_drm_front_drm_pipeline,
+				     pflip_to_worker);
+
+	DRM_ERROR("Frame done timed-out, releasing");
+	send_pending_event(pipeline);
+}
+
+static bool display_send_page_flip(struct drm_simple_display_pipe *pipe,
+				   struct drm_plane_state *old_plane_state)
+{
+	struct drm_plane_state *plane_state =
+			drm_atomic_get_new_plane_state(old_plane_state->state,
+						       &pipe->plane);
+
+	/*
+	 * If old_plane_state->fb is NULL and plane_state->fb is not,
+	 * then this is an atomic commit which will enable display.
+	 * If old_plane_state->fb is not NULL and plane_state->fb is,
+	 * then this is an atomic commit which will disable display.
+	 * Ignore these and do not send page flip as this framebuffer will be
+	 * sent to the backend as a part of display_set_config call.
+	 */
+	if (old_plane_state->fb && plane_state->fb) {
+		struct xen_drm_front_drm_pipeline *pipeline =
+				to_xen_drm_pipeline(pipe);
+		struct xen_drm_front_drm_info *drm_info = pipeline->drm_info;
+		int ret;
+
+		schedule_delayed_work(&pipeline->pflip_to_worker,
+				      msecs_to_jiffies(FRAME_DONE_TO_MS));
+
+		ret = xen_drm_front_page_flip(drm_info->front_info,
+					      pipeline->index,
+					      xen_drm_front_fb_to_cookie(plane_state->fb));
+		if (ret) {
+			DRM_ERROR("Failed to send page flip request to backend: %d\n", ret);
+
+			pipeline->conn_connected = false;
+			/*
+			 * Report the flip not handled, so pending event is
+			 * sent, unblocking user-space.
+			 */
+			return false;
+		}
+		/*
+		 * Signal that page flip was handled, pending event will be sent
+		 * on frame done event from the backend.
+		 */
+		return true;
+	}
+
+	return false;
+}
+
+static int display_check(struct drm_simple_display_pipe *pipe,
+			 struct drm_plane_state *plane_state,
+			 struct drm_crtc_state *crtc_state)
+{
+	/*
+	 * Xen doesn't initialize vblanking via drm_vblank_init(), so
+	 * DRM helpers assume that it doesn't handle vblanking and start
+	 * sending out fake VBLANK events automatically.
+	 *
+	 * As xen contains it's own logic for sending out VBLANK events
+	 * in send_pending_event(), disable no_vblank (i.e., the xen
+	 * driver has vblanking support).
+	 */
+	crtc_state->no_vblank = false;
+
+	return 0;
+}
+
+static void display_update(struct drm_simple_display_pipe *pipe,
+			   struct drm_plane_state *old_plane_state)
+{
+	struct xen_drm_front_drm_pipeline *pipeline =
+			to_xen_drm_pipeline(pipe);
+	struct drm_crtc *crtc = &pipe->crtc;
+	struct drm_pending_vblank_event *event;
+	int idx;
+
+	event = crtc->state->event;
+	if (event) {
+		struct drm_device *dev = crtc->dev;
+		unsigned long flags;
+
+		WARN_ON(pipeline->pending_event);
+
+		spin_lock_irqsave(&dev->event_lock, flags);
+		crtc->state->event = NULL;
+
+		pipeline->pending_event = event;
+		spin_unlock_irqrestore(&dev->event_lock, flags);
+	}
+
+	if (!drm_dev_enter(pipe->crtc.dev, &idx)) {
+		send_pending_event(pipeline);
+		return;
+	}
+
+	/*
+	 * Send page flip request to the backend *after* we have event cached
+	 * above, so on page flip done event from the backend we can
+	 * deliver it and there is no race condition between this code and
+	 * event from the backend.
+	 * If this is not a page flip, e.g. no flip done event from the backend
+	 * is expected, then send now.
+	 */
+	if (!display_send_page_flip(pipe, old_plane_state))
+		send_pending_event(pipeline);
+
+	drm_dev_exit(idx);
+}
+
+static enum drm_mode_status
+display_mode_valid(struct drm_simple_display_pipe *pipe,
+		   const struct drm_display_mode *mode)
+{
+	struct xen_drm_front_drm_pipeline *pipeline =
+			container_of(pipe, struct xen_drm_front_drm_pipeline,
+				     pipe);
+
+	if (mode->hdisplay != pipeline->width)
+		return MODE_ERROR;
+
+	if (mode->vdisplay != pipeline->height)
+		return MODE_ERROR;
+
+	return MODE_OK;
+}
+
+static const struct drm_simple_display_pipe_funcs display_funcs = {
+	.mode_valid = display_mode_valid,
+	.enable = display_enable,
+	.disable = display_disable,
+	.prepare_fb = drm_gem_fb_simple_display_pipe_prepare_fb,
+	.check = display_check,
+	.update = display_update,
+};
+
+static int display_pipe_init(struct xen_drm_front_drm_info *drm_info,
+			     int index, struct xen_drm_front_cfg_connector *cfg,
+			     struct xen_drm_front_drm_pipeline *pipeline)
+{
+	struct drm_device *dev = drm_info->drm_dev;
+	const u32 *formats;
+	int format_count;
+	int ret;
+
+	pipeline->drm_info = drm_info;
+	pipeline->index = index;
+	pipeline->height = cfg->height;
+	pipeline->width = cfg->width;
+
+	INIT_DELAYED_WORK(&pipeline->pflip_to_worker, pflip_to_worker);
+
+	ret = xen_drm_front_conn_init(drm_info, &pipeline->conn);
+	if (ret)
+		return ret;
+
+	formats = xen_drm_front_conn_get_formats(&format_count);
+
+	return drm_simple_display_pipe_init(dev, &pipeline->pipe,
+					    &display_funcs, formats,
+					    format_count, NULL,
+					    &pipeline->conn);
+}
+
+int xen_drm_front_kms_init(struct xen_drm_front_drm_info *drm_info)
+{
+	struct drm_device *dev = drm_info->drm_dev;
+	int i, ret;
+
+	drm_mode_config_init(dev);
+
+	dev->mode_config.min_width = 0;
+	dev->mode_config.min_height = 0;
+	dev->mode_config.max_width = 4095;
+	dev->mode_config.max_height = 2047;
+	dev->mode_config.funcs = &mode_config_funcs;
+
+	for (i = 0; i < drm_info->front_info->cfg.num_connectors; i++) {
+		struct xen_drm_front_cfg_connector *cfg =
+				&drm_info->front_info->cfg.connectors[i];
+		struct xen_drm_front_drm_pipeline *pipeline =
+				&drm_info->pipeline[i];
+
+		ret = display_pipe_init(drm_info, i, cfg, pipeline);
+		if (ret) {
+			drm_mode_config_cleanup(dev);
+			return ret;
+		}
+	}
+
+	drm_mode_config_reset(dev);
+	drm_kms_helper_poll_init(dev);
+	return 0;
+}
+
+void xen_drm_front_kms_fini(struct xen_drm_front_drm_info *drm_info)
+{
+	int i;
+
+	for (i = 0; i < drm_info->front_info->cfg.num_connectors; i++) {
+		struct xen_drm_front_drm_pipeline *pipeline =
+				&drm_info->pipeline[i];
+
+		cancel_delayed_work_sync(&pipeline->pflip_to_worker);
+
+		send_pending_event(pipeline);
+	}
+}

drivers/gpu/drm/xen/xen_drm_front_kms.h

@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+
+/*
+ *  Xen para-virtual DRM device
+ *
+ * Copyright (C) 2016-2018 EPAM Systems Inc.
+ *
+ * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
+ */
+
+#ifndef __XEN_DRM_FRONT_KMS_H_
+#define __XEN_DRM_FRONT_KMS_H_
+
+#include <linux/types.h>
+
+struct xen_drm_front_drm_info;
+struct xen_drm_front_drm_pipeline;
+
+int xen_drm_front_kms_init(struct xen_drm_front_drm_info *drm_info);
+
+void xen_drm_front_kms_fini(struct xen_drm_front_drm_info *drm_info);
+
+void xen_drm_front_kms_on_frame_done(struct xen_drm_front_drm_pipeline *pipeline,
+				     u64 fb_cookie);
+
+#endif /* __XEN_DRM_FRONT_KMS_H_ */