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

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Message-Id: <20211129181723.143657351@linuxfoundation.org>
Date:   Mon, 29 Nov 2021 19:18:41 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mohammed Gamal <mgamal@...hat.com>,
        Deepak Rawat <drawat.floss@...il.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 127/179] drm/hyperv: Fix device removal on Gen1 VMs

From: Mohammed Gamal <mgamal@...hat.com>

[ 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@...hat.com>
Reviewed-by: Deepak Rawat <drawat.floss@...il.com>
Signed-off-by: Deepak Rawat <drawat.floss@...il.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211119112900.300537-1-mgamal@redhat.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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