[PATCH 5.15 127/179] drm/hyperv: Fix device removal on Gen1 VMs

From: Greg Kroah-Hartman
Date: Mon Nov 29 2021 - 13:41:33 EST


From: Mohammed Gamal <mgamal@xxxxxxxxxx>

[ Upstream commit e048834c209a02e3776bcc47d43c6d863e3a67ca ]

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@xxxxxxxxxx>
Reviewed-by: Deepak Rawat <drawat.floss@xxxxxxxxx>
Signed-off-by: Deepak Rawat <drawat.floss@xxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20211119112900.300537-1-mgamal@xxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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 cd818a6291835..00e53de4812bb 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;
}
--
2.33.0