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

[Michael Kelley (LINUX)]

From: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx> Sent: Friday, September 9, 2022 7:44 AM
> 
> 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@xxxxxxxxxxxxxxxxxxx>
> ---
>  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

Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>