Re: [PATCH 1/5] drm/amdgpu: Fix VFCT bus number matching with soft filter

Hello,

On Wed, Jul 08, 2026 at 02:35:14PM -0500, Mario Limonciello wrote:
> On systems where PCI bus renumbering occurs (e.g. pci=realloc,
> resource conflicts), the runtime bus number may differ from the
> BIOS POST bus number recorded in the VFCT table. This causes
> amdgpu_acpi_vfct_bios() to fail finding the VBIOS even though
> the correct device entry exists.
> 
> Introduce amdgpu_acpi_vfct_match() which treats the bus number
> as a soft filter: vendor/device/function identity is the hard
> requirement, while exact bus match is the preferred path. When
> bus numbers disagree but device identity matches, accept the
> VFCT entry and log a dev_notice for diagnostics.
> 
> Reported-by: Oz Tiram <[email protected]>
> Closes: https://lore.kernel.org/amd-gfx/[email protected]/
> Signed-off-by: Mario Limonciello <[email protected]>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c | 45 +++++++++++++++++++++---
>  1 file changed, 40 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c
> index 3ebdd792feec1..d8fd047295d9d 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c
> @@ -377,6 +377,45 @@ static bool amdgpu_read_disabled_bios(struct amdgpu_device *adev)
>  		false : amdgpu_asic_read_disabled_bios(adev);
>  }
>  
> +/**
> + * amdgpu_acpi_vfct_match() - Check if a VFCT entry matches the device
> + * @adev: AMDGPU device
> + * @vhdr: VFCT image header to check
> + *
> + * VFCT entries contain the PCI bus number as recorded during BIOS POST.
> + * On systems where the kernel renumbers PCI buses (e.g. pci=realloc or
> + * resource conflicts), the runtime bus number may differ from the POST
> + * value.  Match by device identity (vendor + device + function) and use
> + * the bus number as a preference: exact bus match is preferred, but when
> + * the bus numbers disagree we accept the entry if the device identity
> + * matches.
> + *
> + * Returns: 0 on match, -ENODEV on no match
> + */
> +static int amdgpu_acpi_vfct_match(struct amdgpu_device *adev,
> +				  VFCT_IMAGE_HEADER *vhdr)
> +{
> +	/* Vendor and device IDs must always match */
> +	if (vhdr->VendorID != adev->pdev->vendor ||
> +	    vhdr->DeviceID != adev->pdev->device)
> +		return -ENODEV;
> +
> +	if (vhdr->PCIDevice != PCI_SLOT(adev->pdev->devfn) ||
> +	    vhdr->PCIFunction != PCI_FUNC(adev->pdev->devfn))
> +		return -ENODEV;
> +
> +	/* Exact bus number match - preferred */
> +	if (vhdr->PCIBus == adev->pdev->bus->number)
> +		return 0;
> +
> +	/* Bus mismatch but device identity matches (PCI renumbering case) */
> +	dev_notice(adev->dev,
> +		   "VFCT bus number mismatch: table %u != runtime %u, matching by device identity (vendor 0x%04x device 0x%04x)\n",
> +		   vhdr->PCIBus, adev->pdev->bus->number,
> +		   adev->pdev->vendor, adev->pdev->device);
> +	return 0;
> +}
> +
>  #ifdef CONFIG_ACPI
>  static bool amdgpu_acpi_vfct_bios(struct amdgpu_device *adev)
>  {
> @@ -413,11 +452,7 @@ static bool amdgpu_acpi_vfct_bios(struct amdgpu_device *adev)
>  		}
>  
>  		if (vhdr->ImageLength &&
> -		    vhdr->PCIBus == adev->pdev->bus->number &&
> -		    vhdr->PCIDevice == PCI_SLOT(adev->pdev->devfn) &&
> -		    vhdr->PCIFunction == PCI_FUNC(adev->pdev->devfn) &&
> -		    vhdr->VendorID == adev->pdev->vendor &&
> -		    vhdr->DeviceID == adev->pdev->device) {
> +		    !amdgpu_acpi_vfct_match(adev, vhdr)) {
>  			adev->bios = kmemdup(&vbios->VbiosContent,
>  					     vhdr->ImageLength,
>  					     GFP_KERNEL);

For the record to hopefully make it easier for others to find the fix:

This patch became 33a18ecd2fbf in

	https://gitlab.freedesktop.org/agd5f/linux.git drm-next

and thus next and it introduces a build failure for !CONFIG_ACPI builds:

	drivers/gpu/drm/radeon/radeon_bios.c:614:12: error: ‘radeon_acpi_vfct_match’ defined but not used [-Werror=unused-function]
	  614 | static int radeon_acpi_vfct_match(struct radeon_device *rdev,
	      |            ^~~~~~~~~~~~~~~~~~~~~~

Patch available at https://lore.kernel.org/all/[email protected]/

Best regards
Uwe

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