Revert "drm/xen-front: Remove CMA support"

This reverts commit 492aec5.

Documentation/gpu/xen-front.rst

@@ -18,6 +18,18 @@ Buffers allocated by the frontend driver
 .. kernel-doc:: drivers/gpu/drm/xen/xen_drm_front.h
    :doc: Buffers allocated by the frontend driver
 
+With GEM CMA helpers
+~~~~~~~~~~~~~~~~~~~~
+
+.. kernel-doc:: drivers/gpu/drm/xen/xen_drm_front.h
+   :doc: With GEM CMA helpers
+
+Without GEM CMA helpers
+~~~~~~~~~~~~~~~~~~~~~~~
+
+.. kernel-doc:: drivers/gpu/drm/xen/xen_drm_front.h
+   :doc: Without GEM CMA helpers
+
 Buffers allocated by the backend
 --------------------------------
 

drivers/gpu/drm/xen/Kconfig

@@ -15,3 +15,16 @@ config DRM_XEN_FRONTEND
 	help
 	  Choose this option if you want to enable a para-virtualized
 	  frontend DRM/KMS driver for Xen guest OSes.
+
+config DRM_XEN_FRONTEND_CMA
+	bool "Use DRM CMA to allocate dumb buffers"
+	depends on DRM_XEN_FRONTEND
+	select DRM_KMS_CMA_HELPER
+	select DRM_GEM_CMA_HELPER
+	help
+	  Use DRM CMA helpers to allocate display buffers.
+	  This is useful for the use-cases when guest driver needs to
+	  share or export buffers to other drivers which only expect
+	  contiguous buffers.
+	  Note: in this mode driver cannot use buffers allocated
+	  by the backend.

drivers/gpu/drm/xen/Makefile

@@ -5,7 +5,12 @@ drm_xen_front-objs := xen_drm_front.o \
 		      xen_drm_front_conn.o \
 		      xen_drm_front_evtchnl.o \
 		      xen_drm_front_shbuf.o \
-		      xen_drm_front_cfg.o \
-		      xen_drm_front_gem.o
+		      xen_drm_front_cfg.o
+
+ifeq ($(CONFIG_DRM_XEN_FRONTEND_CMA),y)
+	drm_xen_front-objs += xen_drm_front_gem_cma.o
+else
+	drm_xen_front-objs += xen_drm_front_gem.o
+endif
 
 obj-$(CONFIG_DRM_XEN_FRONTEND) += drm_xen_front.o

drivers/gpu/drm/xen/xen_drm_front.c

@@ -12,6 +12,7 @@
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_gem.h>
+#include <drm/drm_gem_cma_helper.h>
 
 #include <linux/of_device.h>
 
@@ -166,9 +167,10 @@ int xen_drm_front_mode_set(struct xen_drm_front_drm_pipeline *pipeline,
 	return ret;
 }
 
-int xen_drm_front_dbuf_create(struct xen_drm_front_info *front_info,
+static int be_dbuf_create_int(struct xen_drm_front_info *front_info,
 			      u64 dbuf_cookie, u32 width, u32 height,
-			      u32 bpp, u64 size, struct page **pages)
+			      u32 bpp, u64 size, struct page **pages,
+			      struct sg_table *sgt)
 {
 	struct xen_drm_front_evtchnl *evtchnl;
 	struct xen_drm_front_shbuf *shbuf;
@@ -185,6 +187,7 @@ int xen_drm_front_dbuf_create(struct xen_drm_front_info *front_info,
 	buf_cfg.xb_dev = front_info->xb_dev;
 	buf_cfg.pages = pages;
 	buf_cfg.size = size;
+	buf_cfg.sgt = sgt;
 	buf_cfg.be_alloc = front_info->cfg.be_alloc;
 
 	shbuf = xen_drm_front_shbuf_alloc(&buf_cfg);
@@ -234,6 +237,22 @@ int xen_drm_front_dbuf_create(struct xen_drm_front_info *front_info,
 	return ret;
 }
 
+int xen_drm_front_dbuf_create_from_sgt(struct xen_drm_front_info *front_info,
+				       u64 dbuf_cookie, u32 width, u32 height,
+				       u32 bpp, u64 size, struct sg_table *sgt)
+{
+	return be_dbuf_create_int(front_info, dbuf_cookie, width, height,
+				  bpp, size, NULL, sgt);
+}
+
+int xen_drm_front_dbuf_create_from_pages(struct xen_drm_front_info *front_info,
+					 u64 dbuf_cookie, u32 width, u32 height,
+					 u32 bpp, u64 size, struct page **pages)
+{
+	return be_dbuf_create_int(front_info, dbuf_cookie, width, height,
+				  bpp, size, pages, NULL);
+}
+
 static int xen_drm_front_dbuf_destroy(struct xen_drm_front_info *front_info,
 				      u64 dbuf_cookie)
 {
@@ -415,11 +434,24 @@ static int xen_drm_drv_dumb_create(struct drm_file *filp,
 		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,
-					xen_drm_front_gem_get_pages(obj));
+	/*
+	 * In case of CONFIG_DRM_XEN_FRONTEND_CMA gem_obj is constructed
+	 * via DRM CMA helpers and doesn't have ->pages allocated
+	 * (xendrm_gem_get_pages will return NULL), but instead can provide
+	 * sg table
+	 */
+	if (xen_drm_front_gem_get_pages(obj))
+		ret = xen_drm_front_dbuf_create_from_pages(drm_info->front_info,
+				xen_drm_front_dbuf_to_cookie(obj),
+				args->width, args->height, args->bpp,
+				args->size,
+				xen_drm_front_gem_get_pages(obj));
+	else
+		ret = xen_drm_front_dbuf_create_from_sgt(drm_info->front_info,
+				xen_drm_front_dbuf_to_cookie(obj),
+				args->width, args->height, args->bpp,
+				args->size,
+				xen_drm_front_gem_get_sg_table(obj));
 	if (ret)
 		goto fail_backend;
 
@@ -491,7 +523,11 @@ static const struct file_operations xen_drm_dev_fops = {
 	.poll           = drm_poll,
 	.read           = drm_read,
 	.llseek         = no_llseek,
+#ifdef CONFIG_DRM_XEN_FRONTEND_CMA
+	.mmap           = drm_gem_cma_mmap,
+#else
 	.mmap           = xen_drm_front_gem_mmap,
+#endif
 };
 
 static const struct vm_operations_struct xen_drm_drv_vm_ops = {
@@ -511,9 +547,6 @@ static struct drm_driver xen_drm_driver = {
 	.gem_prime_export          = drm_gem_prime_export,
 	.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",
@@ -522,6 +555,15 @@ static struct drm_driver xen_drm_driver = {
 	.major                     = 1,
 	.minor                     = 0,
 
+#ifdef CONFIG_DRM_XEN_FRONTEND_CMA
+	.gem_prime_vmap            = drm_gem_cma_prime_vmap,
+	.gem_prime_vunmap          = drm_gem_cma_prime_vunmap,
+	.gem_prime_mmap            = drm_gem_cma_prime_mmap,
+#else
+	.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,
+#endif
 };
 
 static int xen_drm_drv_init(struct xen_drm_front_info *front_info)

drivers/gpu/drm/xen/xen_drm_front.h

@@ -23,14 +23,40 @@
  *
  * 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.
+ * host and guest environments, number of operating modes of para-virtualized
+ * display driver are supported:
+ *
+ * - display buffers can be allocated by either frontend driver or backend
+ * - display buffers can be allocated to be contiguous in memory or not
+ *
+ * Note! Frontend driver itself has no dependency on contiguous memory for
+ * its operation.
  */
 
 /**
  * DOC: Buffers allocated by the frontend driver
  *
- * In this mode of operation driver allocates buffers from system memory.
+ * The below modes of operation are configured at compile-time via
+ * frontend driver's kernel configuration:
+ */
+
+/**
+ * DOC: With GEM CMA helpers
+ *
+ * This use-case is useful when used with accompanying DRM/vGPU driver in
+ * guest domain which was designed to only work with contiguous buffers,
+ * e.g. DRM driver based on GEM CMA helpers: such drivers can only import
+ * contiguous PRIME buffers, thus requiring frontend driver to provide
+ * such. In order to implement this mode of operation para-virtualized
+ * frontend driver can be configured to use GEM CMA helpers.
+ */
+
+/**
+ * DOC: Without GEM CMA helpers
+ *
+ * If accompanying drivers can cope with non-contiguous memory then, to
+ * lower pressure on CMA subsystem of the kernel, driver can allocate
+ * 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
@@ -138,9 +164,13 @@ 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, struct page **pages);
+int xen_drm_front_dbuf_create_from_sgt(struct xen_drm_front_info *front_info,
+				       u64 dbuf_cookie, u32 width, u32 height,
+				       u32 bpp, u64 size, struct sg_table *sgt);
+
+int xen_drm_front_dbuf_create_from_pages(struct xen_drm_front_info *front_info,
+					 u64 dbuf_cookie, u32 width, u32 height,
+					 u32 bpp, u64 size, struct page **pages);
 
 int xen_drm_front_fb_attach(struct xen_drm_front_info *front_info,
 			    u64 dbuf_cookie, u64 fb_cookie, u32 width,

drivers/gpu/drm/xen/xen_drm_front_gem.c

@@ -210,9 +210,15 @@ xen_drm_front_gem_import_sg_table(struct drm_device *dev,
 	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, xen_obj->pages);
+	/*
+	 * N.B. Although we have an API to create display buffer from sgt
+	 * we use pages API, because we still need those for GEM handling,
+	 * e.g. for mapping etc.
+	 */
+	ret = xen_drm_front_dbuf_create_from_pages(drm_info->front_info,
+						   xen_drm_front_dbuf_to_cookie(&xen_obj->base),
+						   0, 0, 0, size,
+						   xen_obj->pages);
 	if (ret < 0)
 		return ERR_PTR(ret);
 

drivers/gpu/drm/xen/xen_drm_front_gem.h

@@ -27,6 +27,8 @@ 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);
 
+#ifndef CONFIG_DRM_XEN_FRONTEND_CMA
+
 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);
@@ -36,5 +38,6 @@ void xen_drm_front_gem_prime_vunmap(struct drm_gem_object *gem_obj,
 
 int xen_drm_front_gem_prime_mmap(struct drm_gem_object *gem_obj,
 				 struct vm_area_struct *vma);
+#endif
 
 #endif /* __XEN_DRM_FRONT_GEM_H */

drivers/gpu/drm/xen/xen_drm_front_gem_cma.c

@@ -0,0 +1,79 @@
+// 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/drmP.h>
+#include <drm/drm_gem.h>
+#include <drm/drm_fb_cma_helper.h>
+#include <drm/drm_gem_cma_helper.h>
+
+#include "xen_drm_front.h"
+#include "xen_drm_front_gem.h"
+
+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 drm_gem_object *gem_obj;
+	struct drm_gem_cma_object *cma_obj;
+	int ret;
+
+	gem_obj = drm_gem_cma_prime_import_sg_table(dev, attach, sgt);
+	if (IS_ERR_OR_NULL(gem_obj))
+		return gem_obj;
+
+	cma_obj = to_drm_gem_cma_obj(gem_obj);
+
+	ret = xen_drm_front_dbuf_create_from_sgt(drm_info->front_info,
+						 xen_drm_front_dbuf_to_cookie(gem_obj),
+						 0, 0, 0, gem_obj->size,
+						 drm_gem_cma_prime_get_sg_table(gem_obj));
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	DRM_DEBUG("Imported CMA buffer of size %zu\n", gem_obj->size);
+
+	return gem_obj;
+}
+
+struct sg_table *xen_drm_front_gem_get_sg_table(struct drm_gem_object *gem_obj)
+{
+	return drm_gem_cma_prime_get_sg_table(gem_obj);
+}
+
+struct drm_gem_object *xen_drm_front_gem_create(struct drm_device *dev,
+						size_t size)
+{
+	struct xen_drm_front_drm_info *drm_info = dev->dev_private;
+	struct drm_gem_cma_object *cma_obj;
+
+	if (drm_info->front_info->cfg.be_alloc) {
+		/* This use-case is not yet supported and probably won't be */
+		DRM_ERROR("Backend allocated buffers and CMA helpers are not supported at the same time\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	cma_obj = drm_gem_cma_create(dev, size);
+	if (IS_ERR_OR_NULL(cma_obj))
+		return ERR_CAST(cma_obj);
+
+	return &cma_obj->base;
+}
+
+void xen_drm_front_gem_free_object_unlocked(struct drm_gem_object *gem_obj)
+{
+	drm_gem_cma_free_object(gem_obj);
+}
+
+struct page **xen_drm_front_gem_get_pages(struct drm_gem_object *gem_obj)
+{
+	return NULL;
+}

drivers/gpu/drm/xen/xen_drm_front_shbuf.c

@@ -89,6 +89,10 @@ void xen_drm_front_shbuf_free(struct xen_drm_front_shbuf *buf)
 	}
 	kfree(buf->grefs);
 	kfree(buf->directory);
+	if (buf->sgt) {
+		sg_free_table(buf->sgt);
+		kvfree(buf->pages);
+	}
 	kfree(buf);
 }
 
@@ -346,6 +350,17 @@ static int grant_references(struct xen_drm_front_shbuf *buf)
 
 static int alloc_storage(struct xen_drm_front_shbuf *buf)
 {
+	if (buf->sgt) {
+		buf->pages = kvmalloc_array(buf->num_pages,
+					    sizeof(struct page *), GFP_KERNEL);
+		if (!buf->pages)
+			return -ENOMEM;
+
+		if (drm_prime_sg_to_page_addr_arrays(buf->sgt, buf->pages,
+						     NULL, buf->num_pages) < 0)
+			return -EINVAL;
+	}
+
 	buf->grefs = kcalloc(buf->num_grefs, sizeof(*buf->grefs), GFP_KERNEL);
 	if (!buf->grefs)
 		return -ENOMEM;
@@ -381,6 +396,12 @@ xen_drm_front_shbuf_alloc(struct xen_drm_front_shbuf_cfg *cfg)
 	struct xen_drm_front_shbuf *buf;
 	int ret;
 
+	/* either pages or sgt, not both */
+	if (unlikely(cfg->pages && cfg->sgt)) {
+		DRM_ERROR("Cannot handle buffer allocation with both pages and sg table provided\n");
+		return NULL;
+	}
+
 	buf = kzalloc(sizeof(*buf), GFP_KERNEL);
 	if (!buf)
 		return ERR_PTR(-ENOMEM);
@@ -392,6 +413,7 @@ xen_drm_front_shbuf_alloc(struct xen_drm_front_shbuf_cfg *cfg)
 
 	buf->xb_dev = cfg->xb_dev;
 	buf->num_pages = DIV_ROUND_UP(cfg->size, PAGE_SIZE);
+	buf->sgt = cfg->sgt;
 	buf->pages = cfg->pages;
 
 	buf->ops->calc_num_grefs(buf);