On 3/16/22 15:41, Robin Murphy wrote:
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() ?
Yes, thank you.
However, what about other VirtIO transports? Wouldn't virtio-mmio with F_ACCESS_PLATFORM be in a similar situation?
I couldn't find anyone using virtio-mmio for the GPU, both Qemu and crosvm support only PCI transport for GPU.
But I'm now looking at virtio_mmio_probe() and see that virtio-mmio devices actually should be in the exactly same position as PCI devices. So you should be right and we need to use vdev->dev.parent for the DRM device universally. I'll improve it in the v3, thank you again.