drm/vkms: prime import support

Bring dmabuf sharing through implementing prime_import_sg_table callback.
This will help to validate userspace conformance in prime configurations
without using any actual hardware (e.g. in the cloud).

This enables kms_prime IGT testcase on vkms.

V3:
 - Rodrigo: remove redundant vkms_gem_create_private
V2:
 - Rodrigo: styleguide + return code check

Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Cc: Haneen Mohammed <hamohammed.sa@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Simon Ser <simon.ser@intel.com>
Tested-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Reviewed-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Signed-off-by: Oleg Vasilev <oleg.vasilev@intel.com>
Signed-off-by: Oleg Vasilev <omrigann@gmail.com>
Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190930155924.21845-1-oleg.vasilev@intel.com

drivers/gpu/drm/vkms/vkms_drv.c

@@ -11,7 +11,9 @@
 
 #include <linux/module.h>
 #include <linux/platform_device.h>
+#include <linux/dma-mapping.h>
 
+#include <drm/drm_gem.h>
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_drv.h>
@@ -103,6 +105,8 @@ static struct drm_driver vkms_driver = {
 	.gem_vm_ops		= &vkms_gem_vm_ops,
 	.gem_free_object_unlocked = vkms_gem_free_object,
 	.get_vblank_timestamp	= vkms_get_vblank_timestamp,
+	.prime_fd_to_handle	= drm_gem_prime_fd_to_handle,
+	.gem_prime_import_sg_table = vkms_prime_import_sg_table,
 
 	.name			= DRIVER_NAME,
 	.desc			= DRIVER_DESC,
@@ -157,6 +161,14 @@ static int __init vkms_init(void)
 	if (ret)
 		goto out_unregister;
 
+	ret = dma_coerce_mask_and_coherent(vkms_device->drm.dev,
+					   DMA_BIT_MASK(64));
+
+	if (ret) {
+		DRM_ERROR("Could not initialize DMA support\n");
+		goto out_fini;
+	}
+
 	vkms_device->drm.irq_enabled = true;
 
 	ret = drm_vblank_init(&vkms_device->drm, 1);

drivers/gpu/drm/vkms/vkms_drv.h

@@ -137,6 +137,12 @@ int vkms_gem_vmap(struct drm_gem_object *obj);
 
 void vkms_gem_vunmap(struct drm_gem_object *obj);
 
+/* Prime */
+struct drm_gem_object *
+vkms_prime_import_sg_table(struct drm_device *dev,
+			   struct dma_buf_attachment *attach,
+			   struct sg_table *sg);
+
 /* CRC Support */
 const char *const *vkms_get_crc_sources(struct drm_crtc *crtc,
 					size_t *count);

drivers/gpu/drm/vkms/vkms_gem.c

@@ -1,7 +1,9 @@
 // SPDX-License-Identifier: GPL-2.0+
 
+#include <linux/dma-buf.h>
 #include <linux/shmem_fs.h>
 #include <linux/vmalloc.h>
+#include <drm/drm_prime.h>
 
 #include "vkms_drv.h"
 
@@ -218,3 +220,28 @@ int vkms_gem_vmap(struct drm_gem_object *obj)
 	mutex_unlock(&vkms_obj->pages_lock);
 	return ret;
 }
+
+struct drm_gem_object *
+vkms_prime_import_sg_table(struct drm_device *dev,
+			   struct dma_buf_attachment *attach,
+			   struct sg_table *sg)
+{
+	struct vkms_gem_object *obj;
+	int npages;
+
+	obj = __vkms_gem_create(dev, attach->dmabuf->size);
+	if (IS_ERR(obj))
+		return ERR_CAST(obj);
+
+	npages = PAGE_ALIGN(attach->dmabuf->size) / PAGE_SIZE;
+	DRM_DEBUG_PRIME("Importing %d pages\n", npages);
+
+	obj->pages = kvmalloc_array(npages, sizeof(struct page *), GFP_KERNEL);
+	if (!obj->pages) {
+		vkms_gem_free_object(&obj->gem);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	drm_prime_sg_to_page_addr_arrays(sg, obj->pages, NULL, npages);
+	return &obj->gem;
+}