[PATCH 0/2] Fix amdgpu detection of pci=realloc

[PATCH 0/2] Fix amdgpu detection of pci=realloc

[Mario Limonciello]

amdgpu needs to know the bus number the platform assigned a device to
be able to match firmware images against the right device.

This was previously adjusted to be a soft filter due to
commit 11c141672045f ("drm/amdgpu: Fix VFCT bus number matching with
soft filter") where if everything but the number matched to take a device.

This however fails when there are two identical devices.  Instead save the
initial bus number to the PCI device structure and then match that.

Link: https://lore.kernel.org/linux-pci/20261015124843.203905-1-mario.limonciello@amd.com/
Link: https://lore.kernel.org/amd-gfx/20261019194106.2796150-1-alexander.deucher@amd.com/
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
Mario Limonciello (2):
      PCI: Preserve the initial bus number in pci_dev
      drm/amdgpu: Match VFCT using initial PCI bus number

 drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c | 17 +++--------------
 drivers/pci/probe.c                      |  1 +
 include/linux/pci.h                      |  1 +
 3 files changed, 5 insertions(+), 14 deletions(-)
---
base-commit: 87bba57a9f33e2b5e90d4ad70973675333182a2c
change-id: 20261019-vfct-regression-2142fc52852a

Best regards,
--  
Mario Limonciello <mario.limonciello@amd.com>

[PATCH 1/2] PCI: Preserve the initial bus number in pci_dev

[Mario Limonciello]

PCI bus numbers can be reassigned after device discovery, for example
during resource reallocation. Preserve the number seen at allocation
time so drivers can match devices using firmware-visible bus numbers.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/pci/probe.c | 1 +
 include/linux/pci.h | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 27008e2ea5afc..580b288d5c64f 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2508,6 +2508,7 @@ struct pci_dev *pci_alloc_dev(struct pci_bus *bus)
 	INIT_LIST_HEAD(&dev->bus_list);
 	dev->dev.type = &pci_dev_type;
 	dev->bus = pci_bus_get(bus);
+	dev->initial_bus_number = bus->number;
 	dev->driver_exclusive_resource = (struct resource) {
 		.name = "PCI Exclusive",
 		.start = 0,
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 5ffcf5ce8c966..dae68b28ce051 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -363,6 +363,7 @@ struct pci_dev {
 	struct pci_slot	*slot;		/* Physical slot this device is in */
 
 	unsigned int	devfn;		/* Encoded device & function index */
+	u8		initial_bus_number;	/* Bus number when device was discovered */
 	unsigned short	vendor;
 	unsigned short	device;
 	unsigned short	subsystem_vendor;

-- 
2.43.0

[PATCH 2/2] drm/amdgpu: Match VFCT using initial PCI bus number

[Mario Limonciello]

VFCT records the PCI bus number from BIOS POST. The current bus number
can change after PCI core renumbers the bus, while accepting a mismatch
based only on device identity can select the wrong VFCT image when
matching devices are present. Compare against the bus number captured
when the PCI device was discovered.

Reported-by: Reza Nikzad Chaleshori <rezanikzadch@gmail.com>
Closes: https://lore.kernel.org/amd-gfx/20261014080523.186533-1-rezanikzadch@gmail.com/
Fixes: 11c141672045f ("drm/amdgpu: Fix VFCT bus number matching with soft filter")
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c
index 08ed1eb695586..2b375e6b39d5f 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c
@@ -386,10 +386,8 @@ static bool amdgpu_read_disabled_bios(struct amdgpu_device *adev)
  * 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.
+ * value.  Match using the bus number captured when the device was
+ * discovered, before any bus renumbering.
  *
  * Returns: 0 on match, -ENODEV on no match
  */
@@ -405,16 +403,7 @@ static int amdgpu_acpi_vfct_match(struct amdgpu_device *adev,
 	    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;
+	return vhdr->PCIBus == adev->pdev->initial_bus_number ? 0 : -ENODEV;
 }
 
 static bool amdgpu_acpi_vfct_bios(struct amdgpu_device *adev)

-- 
2.43.0

Re: [PATCH 0/2] Fix amdgpu detection of pci=realloc

[Mario Limonciello]

On 10/19/26 20:44, Mario Limonciello wrote:
> amdgpu needs to know the bus number the platform assigned a device to
> be able to match firmware images against the right device.
> 
> This was previously adjusted to be a soft filter due to
> commit 11c141672045f ("drm/amdgpu: Fix VFCT bus number matching with
> soft filter") where if everything but the number matched to take a device.
> 
> This however fails when there are two identical devices.  Instead save the
> initial bus number to the PCI device structure and then match that.
> 
> Link: https://lore.kernel.org/linux-pci/20261015124843.203905-1-mario.limonciello@amd.com/
> Link: https://lore.kernel.org/amd-gfx/20261019194106.2796150-1-alexander.deucher@amd.com/
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
> Mario Limonciello (2):
>        PCI: Preserve the initial bus number in pci_dev
>        drm/amdgpu: Match VFCT using initial PCI bus number
> 
>   drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c | 17 +++--------------
>   drivers/pci/probe.c                      |  1 +
>   include/linux/pci.h                      |  1 +
>   3 files changed, 5 insertions(+), 14 deletions(-)
> ---
> base-commit: 87bba57a9f33e2b5e90d4ad70973675333182a2c
> change-id: 20261019-vfct-regression-2142fc52852a
> 
> Best regards,
> --
> Mario Limonciello <mario.limonciello@amd.com>

I think Sashiko is right on the feedback.  I'll iterate further on it.