[+cc Alex, Ilpo, Lukas, linux-acpi]
On Thu, Oct 15, 2026 at 07:48:42AM -0500, Mario Limonciello wrote:
> The soft filter system introduced by commit 11c141672045f ("drm/amdgpu:
> Fix VFCT bus number matching with soft filter") has a deficiency that
> it won't work when there are multiple GPUs of the exact same model.
>
> As it was introduced specifically to help the case of pci=realloc, gate
> it to only run when that's in use.
>
> Fixes: 11c141672045f ("drm/amdgpu: Fix VFCT bus number matching with soft
> filter")
> Reported-by: Reza Nikzad Chaleshori <[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 | 15 ++++++++-------
> drivers/pci/setup-bus.c | 5 +++++
> include/linux/pci.h | 1 +
> 3 files changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c
> index 08ed1eb695586..75af9a59671ae 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c
> @@ -384,12 +384,10 @@ static bool amdgpu_read_disabled_bios(struct
> amdgpu_device *adev)
> * @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.
> + * On systems where the user requested PCI resource reallocation, the
> + * runtime bus number may differ from the POST value. Match by device
> + * identity (vendor + device + function), but only treat the bus number as
> + * a preference when pci=realloc was explicitly requested.
This is a generic problem, isn't it?
I think any table from firmware that has PCI bus numbers in it could
trip over issues like this. Seems like we need a more generic
solution.
> *
> * Returns: 0 on match, -ENODEV on no match
> */
> @@ -409,7 +407,10 @@ static int amdgpu_acpi_vfct_match(struct amdgpu_device
> *adev,
> if (vhdr->PCIBus == adev->pdev->bus->number)
> return 0;
>
> - /* Bus mismatch but device identity matches (PCI renumbering case) */
> + /* Allow bus renumbering only when the user requested pci=realloc. */
> + if (!pci_realloc_enabled_by_user())
> + return -ENODEV;
> +
> 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,
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index ed16ef7c26fa7..d9450585082c0 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -1799,6 +1799,11 @@ static bool pci_realloc_enabled(enum enable_type
> enable)
> return enable >= user_enabled;
> }
>
> +bool pci_realloc_enabled_by_user(void)
> +{
> + return pci_realloc_enable == user_enabled;
> +}
I don't like this. I think the same bus renumbering can happen in the
"auto_enabled" case, and I don't think we set pci_realloc_enable in
that case.
But more generally, I think ultimately the PCI core should be able to
reassign bus numbers arbitrarily to accommodate hotplugs (given the
appropriate driver support to tolerate that, of course).
> #if defined(CONFIG_PCI_IOV) && defined(CONFIG_PCI_REALLOC_ENABLE_AUTO)
> static int iov_resources_unassigned(struct pci_dev *dev, void *data)
> {
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index d31a8d107b1ef..844734da9250f 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -610,6 +610,7 @@ static inline struct pci_dev *pci_physfn(struct pci_dev
> *dev)
> }
>
> struct pci_dev *pci_alloc_dev(struct pci_bus *bus);
> +bool pci_realloc_enabled_by_user(void);
>
> #define to_pci_dev(n) container_of(n, struct pci_dev, dev)
> #define for_each_pci_dev(d) while ((d = pci_get_device(PCI_ANY_ID,
> PCI_ANY_ID, d)) != NULL)
> --
> 2.43.0
>
