Re: [PATCH v2 4/8] drm/virtio: Improve DMA API usage for shmem BOs

On 2022-03-14 22:42, Dmitry Osipenko wrote:

DRM API requires the DRM's driver to be backed with the device that can be used for generic DMA operations. The VirtIO-GPU device can't perform DMA operations if it uses PCI transport because PCI device driver creates a virtual VirtIO-GPU device that isn't associated with the PCI. Use PCI's GPU device for the DRM's device instead of the VirtIO-GPU device and drop DMA-related hacks from the VirtIO-GPU driver.

Signed-off-by: Dmitry Osipenko dmitry.osipenko@collabora.com

drivers/gpu/drm/virtio/virtgpu_drv.c | 22 +++++++--- drivers/gpu/drm/virtio/virtgpu_drv.h | 5 +-- drivers/gpu/drm/virtio/virtgpu_kms.c | 7 ++-- drivers/gpu/drm/virtio/virtgpu_object.c | 56 +++++-------------------- drivers/gpu/drm/virtio/virtgpu_vq.c | 13 +++--- 5 files changed, 37 insertions(+), 66 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c index 5f25a8d15464..8449dad3e65c 100644 --- a/drivers/gpu/drm/virtio/virtgpu_drv.c +++ b/drivers/gpu/drm/virtio/virtgpu_drv.c @@ -46,9 +46,9 @@ static int virtio_gpu_modeset = -1; MODULE_PARM_DESC(modeset, "Disable/Enable modesetting"); module_param_named(modeset, virtio_gpu_modeset, int, 0400);

-static int virtio_gpu_pci_quirk(struct drm_device *dev, struct virtio_device *vdev) +static int virtio_gpu_pci_quirk(struct drm_device *dev) {

• struct pci_dev *pdev = to_pci_dev(vdev->dev.parent);

• struct pci_dev *pdev = to_pci_dev(dev->dev); const char *pname = dev_name(&pdev->dev); bool vga = (pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA; char unique[20];

@@ -101,6 +101,7 @@ static int virtio_gpu_pci_quirk(struct drm_device *dev, struct virtio_device *vd static int virtio_gpu_probe(struct virtio_device *vdev) { struct drm_device *dev;

• struct device *dma_dev; int ret;

  if (drm_firmware_drivers_only() && virtio_gpu_modeset == -1)

@@ -109,18 +110,29 @@ static int virtio_gpu_probe(struct virtio_device *vdev) if (virtio_gpu_modeset == 0) return -EINVAL;

• dev = drm_dev_alloc(&driver, &vdev->dev);

• /*

• * If GPU's parent is a PCI device, then we will use this PCI device
  

• * for the DRM's driver device because GPU won't have PCI's IOMMU DMA
  

• * ops in this case since GPU device is sitting on a separate (from PCI)
  

• * virtio-bus.
  

• */
  

• if (!strcmp(vdev->dev.parent->bus->name, "pci"))

Nit: dev_is_pci() ?

However, what about other VirtIO transports? Wouldn't virtio-mmio with F_ACCESS_PLATFORM be in a similar situation?

Robin.

• dma_dev = vdev->dev.parent;
  

• else

• dma_dev = &vdev->dev;
  

• dev = drm_dev_alloc(&driver, dma_dev); if (IS_ERR(dev)) return PTR_ERR(dev); vdev->priv = dev;

  if (!strcmp(vdev->dev.parent->bus->name, "pci")) {

• ret = virtio_gpu_pci_quirk(dev, vdev);
  

• ret = virtio_gpu_pci_quirk(dev);
  

  if (ret) goto err_free; }

• ret = virtio_gpu_init(dev);

• ret = virtio_gpu_init(vdev, dev); if (ret) goto err_free;

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.h b/drivers/gpu/drm/virtio/virtgpu_drv.h index 0a194aaad419..b2d93cb12ebf 100644 --- a/drivers/gpu/drm/virtio/virtgpu_drv.h +++ b/drivers/gpu/drm/virtio/virtgpu_drv.h @@ -100,8 +100,6 @@ struct virtio_gpu_object {

struct virtio_gpu_object_shmem { struct virtio_gpu_object base;

• struct sg_table *pages;

• uint32_t mapped; };

  struct virtio_gpu_object_vram {

@@ -214,7 +212,6 @@ struct virtio_gpu_drv_cap_cache { };

struct virtio_gpu_device {

• struct device *dev; struct drm_device *ddev;

  struct virtio_device *vdev;

@@ -282,7 +279,7 @@ extern struct drm_ioctl_desc virtio_gpu_ioctls[DRM_VIRTIO_NUM_IOCTLS]; void virtio_gpu_create_context(struct drm_device *dev, struct drm_file *file);

/* virtgpu_kms.c */ -int virtio_gpu_init(struct drm_device *dev); +int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev); void virtio_gpu_deinit(struct drm_device *dev); void virtio_gpu_release(struct drm_device *dev); int virtio_gpu_driver_open(struct drm_device *dev, struct drm_file *file); diff --git a/drivers/gpu/drm/virtio/virtgpu_kms.c b/drivers/gpu/drm/virtio/virtgpu_kms.c index 3313b92db531..0d1e3eb61bee 100644 --- a/drivers/gpu/drm/virtio/virtgpu_kms.c +++ b/drivers/gpu/drm/virtio/virtgpu_kms.c @@ -110,7 +110,7 @@ static void virtio_gpu_get_capsets(struct virtio_gpu_device *vgdev, vgdev->num_capsets = num_capsets; }

-int virtio_gpu_init(struct drm_device *dev) +int virtio_gpu_init(struct virtio_device *vdev, struct drm_device *dev) { static vq_callback_t *callbacks[] = { virtio_gpu_ctrl_ack, virtio_gpu_cursor_ack @@ -123,7 +123,7 @@ int virtio_gpu_init(struct drm_device *dev) u32 num_scanouts, num_capsets; int ret = 0;

• if (!virtio_has_feature(dev_to_virtio(dev->dev), VIRTIO_F_VERSION_1))

• if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) return -ENODEV;

  vgdev = kzalloc(sizeof(struct virtio_gpu_device), GFP_KERNEL);

@@ -132,8 +132,7 @@ int virtio_gpu_init(struct drm_device *dev)

vgdev->ddev = dev; dev->dev_private = vgdev;

• vgdev->vdev = dev_to_virtio(dev->dev);
• vgdev->dev = dev->dev;

• vgdev->vdev = vdev;

  spin_lock_init(&vgdev->display_info_lock); spin_lock_init(&vgdev->resource_export_lock);

diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c index 0b8cbb87f8d8..1964c0d8b51f 100644 --- a/drivers/gpu/drm/virtio/virtgpu_object.c +++ b/drivers/gpu/drm/virtio/virtgpu_object.c @@ -67,21 +67,6 @@ void virtio_gpu_cleanup_object(struct virtio_gpu_object *bo)

virtio_gpu_resource_id_put(vgdev, bo->hw_res_handle); if (virtio_gpu_is_shmem(bo)) {

• struct virtio_gpu_object_shmem *shmem = to_virtio_gpu_shmem(bo);
  

• if (shmem->pages) {
  

• 	if (shmem->mapped) {
  

• 		dma_unmap_sgtable(vgdev->vdev->dev.parent,
  

• 			     shmem->pages, DMA_TO_DEVICE, 0);
  

• 		shmem->mapped = 0;
  

• 	}
  

• 	sg_free_table(shmem->pages);
  

• 	kfree(shmem->pages);
  

• 	shmem->pages = NULL;
  

• 	drm_gem_shmem_unpin(&bo->base);
  

• }
  

• drm_gem_shmem_free(&bo->base); } else if (virtio_gpu_is_vram(bo)) { struct virtio_gpu_object_vram *vram = to_virtio_gpu_vram(bo);

@@ -153,37 +138,18 @@ static int virtio_gpu_object_shmem_init(struct virtio_gpu_device *vgdev, unsigned int *nents) { bool use_dma_api = !virtio_has_dma_quirk(vgdev->vdev);

• struct virtio_gpu_object_shmem *shmem = to_virtio_gpu_shmem(bo); struct scatterlist *sg;
• int si, ret;

• struct sg_table *pages;
• int si;

• ret = drm_gem_shmem_pin(&bo->base);
• if (ret < 0)

• return -EINVAL;
  

• /*

• * virtio_gpu uses drm_gem_shmem_get_sg_table instead of
  

• * drm_gem_shmem_get_pages_sgt because virtio has it's own set of
  

• * dma-ops. This is discouraged for other drivers, but should be fine
  

• * since virtio_gpu doesn't support dma-buf import from other devices.
  

• */
  

• shmem->pages = drm_gem_shmem_get_sg_table(&bo->base);
• ret = PTR_ERR(shmem->pages);
• if (ret) {

• drm_gem_shmem_unpin(&bo->base);
  

• shmem->pages = NULL;
  

• return ret;
  

• }

• pages = drm_gem_shmem_get_pages_sgt(&bo->base);
• if (IS_ERR(pages))

• return PTR_ERR(pages);
  
  

• if (use_dma_api) {

• ret = dma_map_sgtable(vgdev->vdev->dev.parent,
  

• 		      shmem->pages, DMA_TO_DEVICE, 0);
  

• if (ret)
  

• 	return ret;
  

• *nents = shmem->mapped = shmem->pages->nents;
  

• } else {

• *nents = shmem->pages->orig_nents;
  

• }

• if (use_dma_api)

• *nents = pages->nents;
  

• else

• *nents = pages->orig_nents;
  
  

  *ents = kvmalloc_array(*nents, sizeof(struct virtio_gpu_mem_entry),

@@ -194,13 +160,13 @@ static int virtio_gpu_object_shmem_init(struct virtio_gpu_device *vgdev, }

if (use_dma_api) {

• for_each_sgtable_dma_sg(shmem->pages, sg, si) {
  

• for_each_sgtable_dma_sg(pages, sg, si) {
  (*ents)[si].addr = cpu_to_le64(sg_dma_address(sg));
  (*ents)[si].length = cpu_to_le32(sg_dma_len(sg));
  (*ents)[si].padding = 0;
  

  } } else {

• for_each_sgtable_sg(shmem->pages, sg, si) {
  

• for_each_sgtable_sg(pages, sg, si) {
  (*ents)[si].addr = cpu_to_le64(sg_phys(sg));
  (*ents)[si].length = cpu_to_le32(sg->length);
  (*ents)[si].padding = 0;
  

diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virtio/virtgpu_vq.c index 2edf31806b74..06566e44307d 100644 --- a/drivers/gpu/drm/virtio/virtgpu_vq.c +++ b/drivers/gpu/drm/virtio/virtgpu_vq.c @@ -593,11 +593,10 @@ void virtio_gpu_cmd_transfer_to_host_2d(struct virtio_gpu_device *vgdev, struct virtio_gpu_transfer_to_host_2d *cmd_p; struct virtio_gpu_vbuffer *vbuf; bool use_dma_api = !virtio_has_dma_quirk(vgdev->vdev);

• struct virtio_gpu_object_shmem *shmem = to_virtio_gpu_shmem(bo);

  if (virtio_gpu_is_shmem(bo) && use_dma_api)

• dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
  

• 			    shmem->pages, DMA_TO_DEVICE);
  

• dma_sync_sgtable_for_device(&vgdev->vdev->dev,
  

• 			    bo->base.sgt, DMA_TO_DEVICE);
  
  

  cmd_p = virtio_gpu_alloc_cmd(vgdev, &vbuf, sizeof(*cmd_p)); memset(cmd_p, 0, sizeof(*cmd_p));

@@ -1017,11 +1016,9 @@ void virtio_gpu_cmd_transfer_to_host_3d(struct virtio_gpu_device *vgdev, struct virtio_gpu_vbuffer *vbuf; bool use_dma_api = !virtio_has_dma_quirk(vgdev->vdev);

• if (virtio_gpu_is_shmem(bo) && use_dma_api) {

• struct virtio_gpu_object_shmem *shmem = to_virtio_gpu_shmem(bo);
  

• dma_sync_sgtable_for_device(vgdev->vdev->dev.parent,
  

• 			    shmem->pages, DMA_TO_DEVICE);
  

• }

• if (virtio_gpu_is_shmem(bo) && use_dma_api)

• dma_sync_sgtable_for_device(&vgdev->vdev->dev,
  

• 			    bo->base.sgt, DMA_TO_DEVICE);
  
  

  cmd_p = virtio_gpu_alloc_cmd(vgdev, &vbuf, sizeof(*cmd_p)); memset(cmd_p, 0, sizeof(*cmd_p));