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Message-ID: <f2fed903-c61b-8040-ddfd-25a7bf0a625a@arm.com>
Date: Wed, 16 Mar 2022 12:41:46 +0000
From: Robin Murphy <robin.murphy@....com>
To: Dmitry Osipenko <dmitry.osipenko@...labora.com>,
David Airlie <airlied@...ux.ie>,
Gerd Hoffmann <kraxel@...hat.com>,
Gurchetan Singh <gurchetansingh@...omium.org>,
Chia-I Wu <olvaffe@...il.com>, Daniel Vetter <daniel@...ll.ch>,
Daniel Almeida <daniel.almeida@...labora.com>,
Gert Wollny <gert.wollny@...labora.com>,
Tomeu Vizoso <tomeu.vizoso@...labora.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
Rob Herring <robh@...nel.org>,
Steven Price <steven.price@....com>,
Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>
Cc: linux-kernel@...r.kernel.org,
virtualization@...ts.linux-foundation.org,
Gustavo Padovan <gustavo.padovan@...labora.com>,
dri-devel@...ts.freedesktop.org, Dmitry Osipenko <digetx@...il.com>
Subject: 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@...labora.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));
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