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@xxxxxxxxxxxxx> >> --- >> 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.