drm/virtio: Add a helper to map and note the dma addrs and lengths

This helper would be used when first initializing the object as
part of import and also when updating the plane where we need to
ensure that the imported object's backing is valid.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Gurchetan Singh <gurchetansingh@chromium.org>
Cc: Chia-I Wu <olvaffe@gmail.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241126031643.3490496-3-vivek.kasireddy@intel.com

drivers/gpu/drm/virtio/virtgpu_drv.h

@@ -89,6 +89,7 @@ struct virtio_gpu_object_params {
 
 struct virtio_gpu_object {
 	struct drm_gem_shmem_object base;
+	struct sg_table *sgt;
 	uint32_t hw_res_handle;
 	bool dumb;
 	bool created;
@@ -477,6 +478,10 @@ struct drm_gem_object *virtgpu_gem_prime_import(struct drm_device *dev,
 struct drm_gem_object *virtgpu_gem_prime_import_sg_table(
 	struct drm_device *dev, struct dma_buf_attachment *attach,
 	struct sg_table *sgt);
+int virtgpu_dma_buf_import_sgt(struct virtio_gpu_mem_entry **ents,
+			       unsigned int *nents,
+			       struct virtio_gpu_object *bo,
+			       struct dma_buf_attachment *attach);
 
 /* virtgpu_debugfs.c */
 void virtio_gpu_debugfs_init(struct drm_minor *minor);

drivers/gpu/drm/virtio/virtgpu_prime.c

@@ -27,6 +27,8 @@
 
 #include "virtgpu_drv.h"
 
+MODULE_IMPORT_NS(DMA_BUF);
+
 static int virtgpu_virtio_get_uuid(struct dma_buf *buf,
 				   uuid_t *uuid)
 {
@@ -142,6 +144,46 @@ struct dma_buf *virtgpu_gem_prime_export(struct drm_gem_object *obj,
 	return buf;
 }
 
+int virtgpu_dma_buf_import_sgt(struct virtio_gpu_mem_entry **ents,
+			       unsigned int *nents,
+			       struct virtio_gpu_object *bo,
+			       struct dma_buf_attachment *attach)
+{
+	struct scatterlist *sl;
+	struct sg_table *sgt;
+	long i, ret;
+
+	dma_resv_assert_held(attach->dmabuf->resv);
+
+	ret = dma_resv_wait_timeout(attach->dmabuf->resv,
+				    DMA_RESV_USAGE_KERNEL,
+				    false, MAX_SCHEDULE_TIMEOUT);
+	if (ret <= 0)
+		return ret < 0 ? ret : -ETIMEDOUT;
+
+	sgt = dma_buf_map_attachment(attach, DMA_BIDIRECTIONAL);
+	if (IS_ERR(sgt))
+		return PTR_ERR(sgt);
+
+	*ents = kvmalloc_array(sgt->nents,
+			       sizeof(struct virtio_gpu_mem_entry),
+			       GFP_KERNEL);
+	if (!(*ents)) {
+		dma_buf_unmap_attachment(attach, sgt, DMA_BIDIRECTIONAL);
+		return -ENOMEM;
+	}
+
+	*nents = sgt->nents;
+	for_each_sgtable_dma_sg(sgt, sl, i) {
+		(*ents)[i].addr = cpu_to_le64(sg_dma_address(sl));
+		(*ents)[i].length = cpu_to_le32(sg_dma_len(sl));
+		(*ents)[i].padding = 0;
+	}
+
+	bo->sgt = sgt;
+	return 0;
+}
+
 struct drm_gem_object *virtgpu_gem_prime_import(struct drm_device *dev,
 						struct dma_buf *buf)
 {