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);
-- 
2.43.0

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