drm/virtio: Improve DMA API usage for shmem BOs

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>
Link: http://patchwork.freedesktop.org/patch/msgid/20220630200726.1884320-8-dmitry.osipenko@collabora.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c
index 5f25a8d..0141b7d 100644 (file)
--- a/drivers/gpu/drm/virtio/virtgpu_drv.c
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.c
@@ -46,12 +46,11 @@ 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];
        int ret;
 
        DRM_INFO("pci: %s detected at %s\n",
@@ -63,39 +62,7 @@ static int virtio_gpu_pci_quirk(struct drm_device *dev, struct virtio_device *vd
                        return ret;
        }
 
-       /*
-        * Normally the drm_dev_set_unique() call is done by core DRM.
-        * The following comment covers, why virtio cannot rely on it.
-        *
-        * Unlike the other virtual GPU drivers, virtio abstracts the
-        * underlying bus type by using struct virtio_device.
-        *
-        * Hence the dev_is_pci() check, used in core DRM, will fail
-        * and the unique returned will be the virtio_device "virtio0",
-        * while a "pci:..." one is required.
-        *
-        * A few other ideas were considered:
-        * - Extend the dev_is_pci() check [in drm_set_busid] to
-        *   consider virtio.
-        *   Seems like a bigger hack than what we have already.
-        *
-        * - Point drm_device::dev to the parent of the virtio_device
-        *   Semantic changes:
-        *   * Using the wrong device for i2c, framebuffer_alloc and
-        *     prime import.
-        *   Visual changes:
-        *   * Helpers such as DRM_DEV_ERROR, dev_info, drm_printer,
-        *     will print the wrong information.
-        *
-        * We could address the latter issues, by introducing
-        * drm_device::bus_dev, ... which would be used solely for this.
-        *
-        * So for the moment keep things as-is, with a bulky comment
-        * for the next person who feels like removing this
-        * drm_dev_set_unique() quirk.
-        */
-       snprintf(unique, sizeof(unique), "pci:%s", pname);
-       return drm_dev_set_unique(dev, unique);
+       return 0;
 }
 
 static int virtio_gpu_probe(struct virtio_device *vdev)
@@ -109,18 +76,24 @@ static int virtio_gpu_probe(struct virtio_device *vdev)
        if (virtio_gpu_modeset == 0)
                return -EINVAL;
 
-       dev = drm_dev_alloc(&driver, &vdev->dev);
+       /*
+        * The virtio-gpu device is a virtual device that doesn't have DMA
+        * ops assigned to it, nor DMA mask set and etc. Its parent device
+        * is actual GPU device we want to use it for the DRM's device in
+        * order to benefit from using generic DRM APIs.
+        */
+       dev = drm_dev_alloc(&driver, vdev->dev.parent);
        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 f80664c..9b98470 100644 (file)
--- a/drivers/gpu/drm/virtio/virtgpu_drv.h
+++ b/drivers/gpu/drm/virtio/virtgpu_drv.h
@@ -101,8 +101,6 @@ 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 {
@@ -215,7 +213,6 @@ struct virtio_gpu_drv_cap_cache {
 };
 
 struct virtio_gpu_device {
-       struct device *dev;
        struct drm_device *ddev;
 
        struct virtio_device *vdev;
@@ -283,7 +280,7 @@ 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 3313b92..0d1e3eb 100644 (file)
--- 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 62b4d07..8d77281 100644 (file)
--- 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);
@@ -153,36 +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);
-       if (IS_ERR(shmem->pages)) {
-               drm_gem_shmem_unpin(&bo->base);
-               shmem->pages = NULL;
-               return PTR_ERR(shmem->pages);
-       }
+       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),
@@ -193,13 +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 1262fd0..ee84256 100644 (file)
--- a/drivers/gpu/drm/virtio/virtgpu_vq.c
+++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
@@ -595,11 +595,10 @@ 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));
@@ -1019,11 +1018,9 @@ 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));