linux-kernel - [PATCH] drm/hyperv: Don't rely on screen_info.lfb

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Date:   Fri,  9 Sep 2022 07:43:59 -0700
From:   Saurabh Sengar <ssengar@...ux.microsoft.com>
To:     ssengar@...rosoft.com, drawat.floss@...il.com, airlied@...ux.ie,
        daniel@...ll.ch, linux-hyperv@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        mikelley@...rosoft.com
Subject: [PATCH] drm/hyperv: Don't rely on screen_info.lfb_base for Gen1 VMs

hyperv_setup_vram tries to remove conflicting framebuffer based on
'screen_info'. As observed in past due to some bug or wrong setting
in grub, the 'screen_info' fields may not be set for Gen1, and in such
cases drm_aperture_remove_conflicting_framebuffers will not do anything
useful.
For Gen1 VMs, it should always be possible to get framebuffer
conflict removed using PCI device instead.

Fixes: a0ab5abced55 ("drm/hyperv : Removing the restruction of VRAM allocation with PCI bar size")
Signed-off-by: Saurabh Sengar <ssengar@...ux.microsoft.com>
---
 drivers/gpu/drm/hyperv/hyperv_drm_drv.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_drv.c b/drivers/gpu/drm/hyperv/hyperv_drm_drv.c
index 6d11e7938c83..b0cc974efa45 100644
--- a/drivers/gpu/drm/hyperv/hyperv_drm_drv.c
+++ b/drivers/gpu/drm/hyperv/hyperv_drm_drv.c
@@ -73,12 +73,28 @@ static int hyperv_setup_vram(struct hyperv_drm_device *hv,
 			     struct hv_device *hdev)
 {
 	struct drm_device *dev = &hv->dev;
+	struct pci_dev *pdev;
 	int ret;
 
-	drm_aperture_remove_conflicting_framebuffers(screen_info.lfb_base,
-						     screen_info.lfb_size,
-						     false,
-						     &hyperv_driver);
+	if (efi_enabled(EFI_BOOT)) {
+		drm_aperture_remove_conflicting_framebuffers(screen_info.lfb_base,
+							     screen_info.lfb_size,
+							     false,
+							     &hyperv_driver);
+	} 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;
+		}
+
+		ret = drm_aperture_remove_conflicting_pci_framebuffers(pdev, &hyperv_driver);
+		pci_dev_put(pdev);
+		if (ret) {
+			drm_err(dev, "Not able to remove boot fb\n");
+			return ret;
+		}
+	}
 
 	hv->fb_size = (unsigned long)hv->mmio_megabytes * 1024 * 1024;
 
-- 
2.34.1