Re: [PATCH] drm/hyperv: Don't rely on screen_info.lfb_base for Gen1 VMs

[Thomas Zimmermann]

Hi

Am 09.09.22 um 16:43 schrieb Saurabh Sengar:

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 <ssen...@linux.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;

-                                                    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,

- drm_aperture_remove_conflicting_framebuffers(screen_info.lfb_base,

Best regard
Thomas

Using screen_info here seems wrong in any case. You want to remove the framebuffer devices that conflict with your driver, which might be unrelated to screen_info. AFAICT the correct solution would always retrieve the PCI device for removal (i.e., always do the else branch).

+                                                            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;

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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