Thanks for the patch.

Reviewed-by: Deepak Rawat drawat.floss@gmail.com

I will push this to drm-fixes, let me know otherwise.

Deepak

On Fri, 2021-11-19 at 12:29 +0100, Mohammed Gamal wrote:

The Hyper-V DRM driver tries to free MMIO region on removing the device regardless of VM type, while Gen1 VMs don't use MMIO and hence causing the kernel to crash on a NULL pointer dereference.

Fix this by making deallocating MMIO only on Gen2 machines and implement removal for Gen1

Fixes: 76c56a5affeb ("drm/hyperv: Add DRM driver for hyperv synthetic video device")

Signed-off-by: Mohammed Gamal mgamal@redhat.com

drivers/gpu/drm/hyperv/hyperv_drm_drv.c | 19 ++++++++++++++++++-  1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_drv.c b/drivers/gpu/drm/hyperv/hyperv_drm_drv.c index cd818a629183..9f923beb7d8d 100644 --- a/drivers/gpu/drm/hyperv/hyperv_drm_drv.c +++ b/drivers/gpu/drm/hyperv/hyperv_drm_drv.c @@ -225,12 +225,29 @@ static int hyperv_vmbus_remove(struct hv_device *hdev)  {         struct drm_device *dev = hv_get_drvdata(hdev);         struct hyperv_drm_device *hv = to_hv(dev); +       struct pci_dev *pdev;           drm_dev_unplug(dev);         drm_atomic_helper_shutdown(dev);         vmbus_close(hdev->channel);         hv_set_drvdata(hdev, NULL); -       vmbus_free_mmio(hv->mem->start, hv->fb_size);

+       /* +        * Free allocated MMIO memory only on Gen2 VMs. +        * On Gen1 VMs, release the PCI device +        */ +       if (efi_enabled(EFI_BOOT)) { +               vmbus_free_mmio(hv->mem->start, hv->fb_size); +       } else { +               pdev = pci_get_device(PCI_VENDOR_ID_MICROSOFT, +                               PCI_DEVICE_ID_HYPERV_VIDEO, NULL); +               if (!pdev) { +                       drm_err(dev, "Unable to find PCI Hyper-V video\n"); +                       return -ENODEV; +               } +               pci_release_region(pdev, 0); +               pci_dev_put(pdev); +       }           return 0;  }