2021-11-19 11:29:26

by Mohammed Gamal

Subject: [PATCH] drm/hyperv: Fix device removal on Gen1 VMs

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 <[email protected]>
---
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;
}
--
2.33.1

2021-11-20 00:42:33

by Deepak Rawat

Subject: Re: [PATCH] drm/hyperv: Fix device removal on Gen1 VMs

Thanks for the patch.

Reviewed-by: Deepak Rawat <[email protected]>

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 <[email protected]>
> ---
>  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;
>  }