[PATCH v6 13/22] drm/virtio: Improve DMA API usage for shmem BOs

Dmitry Osipenko
2022-05-26T23:55:50Z

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 | 51 ++++++----------------
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, 32 insertions(+), 100 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_drv.c b/drivers/gpu/drm/virtio/virtgpu_drv.c
index 5f25a8d15464..0141b7df97ec 100644
--- 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 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 18f70ef6b4d0..8d7728181de0 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_OR_ZERO(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));
--
2.35.3