* [PATCH v7 1/3] PCI: Cache bridge firmware secondary bus number
2026-11-12 21:54 [PATCH v7 0/3] Fix VFCT matching after PCI bus renumbering Mario Limonciello
@ 2026-11-12 21:54 ` Mario Limonciello
2026-11-13 1:05 ` sashiko-bot
2026-11-12 21:54 ` [PATCH v7 2/3] drm/amdgpu: Match VFCT using initial PCI " Mario Limonciello
2026-11-12 21:54 ` [PATCH v7 3/3] drm/radeon: " Mario Limonciello
2 siblings, 1 reply; 7+ messages in thread
From: Mario Limonciello @ 2026-11-12 21:54 UTC (permalink / raw)
To: Bjorn Helgaas, Alex Deucher, Christian König
Cc: Oz Tiram, linux-pci, linux-kernel, amd-gfx, dri-devel,
Mario Limonciello
Drivers such as amdgpu and radeon need the bus number firmware assigned
to a device to match it against firmware tables like VFCT. The PCI core
may renumber buses (e.g. with pci=realloc), after which the runtime
number no longer reflects what firmware programmed.
Record the firmware secondary bus number on the bridge's struct pci_dev
the first time pci_read_bridge_windows() reads the bridge's bus numbers,
which happens before any renumbering. Devices behind the bridge can then
retrieve the original bus number via their upstream bridge.
Only store the value if it is usable: ignore unconfigured (0) and 0xff
secondaries. Use a separate "sampled" flag so that later rescans, which
would read the renumbered runtime value, never overwrite the cached
number, and a "valid" flag so users can tell whether anything was
recorded.
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
drivers/pci/probe.c | 16 ++++++++++++++--
include/linux/pci.h | 4 ++++
2 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 27008e2ea5afc..f20a4b8f7a23b 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -505,14 +505,26 @@ static void pci_read_bridge_mmio_pref(struct pci_dev *dev, struct resource *res,
static void pci_read_bridge_windows(struct pci_dev *bridge)
{
u32 buses;
+ u8 secondary;
+ u8 subordinate;
u16 io;
u32 pmem, tmp;
struct resource res;
pci_read_config_dword(bridge, PCI_PRIMARY_BUS, &buses);
res.flags = IORESOURCE_BUS;
- res.start = FIELD_GET(PCI_SECONDARY_BUS_MASK, buses);
- res.end = FIELD_GET(PCI_SUBORDINATE_BUS_MASK, buses);
+ secondary = FIELD_GET(PCI_SECONDARY_BUS_MASK, buses);
+ subordinate = FIELD_GET(PCI_SUBORDINATE_BUS_MASK, buses);
+ res.start = secondary;
+ res.end = subordinate;
+
+ if (!bridge->fw_sec_bus_sampled) {
+ bridge->fw_sec_bus_sampled = true;
+ if (secondary > 0 && secondary < 0xff) {
+ bridge->fw_sec_busnr = secondary;
+ bridge->fw_sec_bus_valid = true;
+ }
+ }
pci_info(bridge, "PCI bridge to %pR%s\n", &res,
bridge->transparent ? " (subtractive decode)" : "");
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 5ffcf5ce8c966..045157488b8e7 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -363,6 +363,8 @@ struct pci_dev {
struct pci_slot *slot; /* Physical slot this device is in */
unsigned int devfn; /* Encoded device & function index */
+ /* Firmware secondary bus number saved across bridge scan passes */
+ unsigned char fw_sec_busnr;
unsigned short vendor;
unsigned short device;
unsigned short subsystem_vendor;
@@ -414,6 +416,8 @@ struct pci_dev {
unsigned int pme_poll:1; /* Poll device's PME status bit */
unsigned int pinned:1; /* Whether this dev is pinned */
unsigned int config_rrs_sv:1; /* Config RRS software visibility */
+ unsigned int fw_sec_bus_valid:1; /* Firmware secondary bus number usable */
+ unsigned int fw_sec_bus_sampled:1; /* Firmware secondary bus number captured */
unsigned int imm_ready:1; /* Supports Immediate Readiness */
unsigned int d1_support:1; /* Low power state D1 is supported */
unsigned int d2_support:1; /* Low power state D2 is supported */
--
2.43.0
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH v7 1/3] PCI: Cache bridge firmware secondary bus number
2026-11-12 21:54 ` [PATCH v7 1/3] PCI: Cache bridge firmware secondary bus number Mario Limonciello
@ 2026-11-13 1:05 ` sashiko-bot
0 siblings, 0 replies; 7+ messages in thread
From: sashiko-bot @ 2026-11-13 1:05 UTC (permalink / raw)
To: Mario Limonciello; +Cc: linux-pci, amd-gfx, dri-devel
Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] PCI: dead fw_sec_bus_sampled in pci_read_bridge_windows() and
log mismatch
--
commit d3720492f32e5a284ef73b3dc9f69d02b13df2c4
Author: Mario Limonciello <mario.limonciello@amd.com>
PCI: Cache bridge firmware secondary bus number
This commit caches the firmware-assigned secondary bus number on a PCI
bridge's struct pci_dev in pci_read_bridge_windows() before bus renumbering
can occur.
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 27008e2ea5afc..f20a4b8f7a23b 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -505,14 +505,26 @@ static void pci_read_bridge_mmio_pref(struct pci_dev *dev, struct resource *res,
> static void pci_read_bridge_windows(struct pci_dev *bridge)
> {
> u32 buses;
> + u8 secondary;
> + u8 subordinate;
> u16 io;
> u32 pmem, tmp;
> struct resource res;
>
> pci_read_config_dword(bridge, PCI_PRIMARY_BUS, &buses);
> res.flags = IORESOURCE_BUS;
> - res.start = FIELD_GET(PCI_SECONDARY_BUS_MASK, buses);
> - res.end = FIELD_GET(PCI_SUBORDINATE_BUS_MASK, buses);
> + secondary = FIELD_GET(PCI_SECONDARY_BUS_MASK, buses);
> + subordinate = FIELD_GET(PCI_SUBORDINATE_BUS_MASK, buses);
> + res.start = secondary;
> + res.end = subordinate;
> +
> + if (!bridge->fw_sec_bus_sampled) {
> + bridge->fw_sec_bus_sampled = true;
> + if (secondary > 0 && secondary < 0xff) {
> + bridge->fw_sec_busnr = secondary;
> + bridge->fw_sec_bus_valid = true;
> + }
> + }
[Severity: Low]
As reported by Lazar, Lijo on v5 [1], is bridge->fw_sec_bus_sampled needed
here?
pci_read_bridge_windows() is only called from pci_setup_device() when
pci_scan_device() first allocates and initializes a new struct pci_dev. On
later bus rescans, pci_scan_single_device() finds the existing device via
pci_get_slot() and returns early without calling pci_setup_device() or
pci_read_bridge_windows(). Because pci_read_bridge_windows() runs at most
once per bridge instance on a zero-initialized struct pci_dev,
fw_sec_bus_sampled is always false on entry and is never read elsewhere,
making the bitfield and the commit message's rescan explanation unnecessary.
In addition, since bus 0 is the root bus and fw_sec_busnr is only set when
secondary > 0 && secondary < 0xff, fw_sec_bus_valid is redundant with
checking whether fw_sec_busnr is non-zero.
[1] https://lore.kernel.org/r/eba45235-a6b1-4a48-9c56-9e069c299478@amd.com
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261112-vfct-regression-v7-0-69b1e0cf45c2@amd.com?part=1
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH v7 2/3] drm/amdgpu: Match VFCT using initial PCI bus number
2026-11-12 21:54 [PATCH v7 0/3] Fix VFCT matching after PCI bus renumbering Mario Limonciello
2026-11-12 21:54 ` [PATCH v7 1/3] PCI: Cache bridge firmware secondary bus number Mario Limonciello
@ 2026-11-12 21:54 ` Mario Limonciello
2026-11-13 0:59 ` sashiko-bot
2026-11-12 21:54 ` [PATCH v7 3/3] drm/radeon: " Mario Limonciello
2 siblings, 1 reply; 7+ messages in thread
From: Mario Limonciello @ 2026-11-12 21:54 UTC (permalink / raw)
To: Bjorn Helgaas, Alex Deucher, Christian König
Cc: Oz Tiram, linux-pci, linux-kernel, amd-gfx, dri-devel,
Mario Limonciello, Reza Nikzad Chaleshori
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
from the firmware bus assignment before bridge renumbering.
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 | 23 ++++++++++-------------
1 file changed, 10 insertions(+), 13 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c
index 08ed1eb695586..0ee4c6462c4d0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c
@@ -386,16 +386,17 @@ 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
*/
static int amdgpu_acpi_vfct_match(struct amdgpu_device *adev,
VFCT_IMAGE_HEADER *vhdr)
{
+ struct pci_dev *bridge = adev->pdev->bus->self;
+ unsigned char initial_bus;
+
/* Vendor and device IDs must always match */
if (vhdr->VendorID != adev->pdev->vendor ||
vhdr->DeviceID != adev->pdev->device)
@@ -405,16 +406,12 @@ 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;
+ if (bridge && bridge->fw_sec_bus_valid)
+ initial_bus = bridge->fw_sec_busnr;
+ else
+ initial_bus = adev->pdev->bus->number;
- /* 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 == initial_bus ? 0 : -ENODEV;
}
static bool amdgpu_acpi_vfct_bios(struct amdgpu_device *adev)
--
2.43.0
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH v7 3/3] drm/radeon: Match VFCT using initial PCI bus number
2026-11-12 21:54 [PATCH v7 0/3] Fix VFCT matching after PCI bus renumbering Mario Limonciello
2026-11-12 21:54 ` [PATCH v7 1/3] PCI: Cache bridge firmware secondary bus number Mario Limonciello
2026-11-12 21:54 ` [PATCH v7 2/3] drm/amdgpu: Match VFCT using initial PCI " Mario Limonciello
@ 2026-11-12 21:54 ` Mario Limonciello
2026-11-13 0:58 ` sashiko-bot
2 siblings, 1 reply; 7+ messages in thread
From: Mario Limonciello @ 2026-11-12 21:54 UTC (permalink / raw)
To: Bjorn Helgaas, Alex Deucher, Christian König
Cc: Oz Tiram, linux-pci, linux-kernel, amd-gfx, dri-devel,
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
from the firmware bus assignment before bridge renumbering.
Fixes: 4059e2f02c8a ("drm/radeon: Fix VFCT bus number matching with soft filter")
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
drivers/gpu/drm/radeon/radeon_bios.c | 25 +++++++++++--------------
1 file changed, 11 insertions(+), 14 deletions(-)
diff --git a/drivers/gpu/drm/radeon/radeon_bios.c b/drivers/gpu/drm/radeon/radeon_bios.c
index 1da6bf1c17ff3..707566e376d05 100644
--- a/drivers/gpu/drm/radeon/radeon_bios.c
+++ b/drivers/gpu/drm/radeon/radeon_bios.c
@@ -609,16 +609,17 @@ static bool radeon_read_disabled_bios(struct radeon_device *rdev)
* 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
*/
static int radeon_acpi_vfct_match(struct radeon_device *rdev,
- VFCT_IMAGE_HEADER *vhdr)
+ VFCT_IMAGE_HEADER *vhdr)
{
+ struct pci_dev *bridge = rdev->pdev->bus->self;
+ unsigned char initial_bus;
+
/* Vendor and device IDs must always match */
if (vhdr->VendorID != rdev->pdev->vendor ||
vhdr->DeviceID != rdev->pdev->device)
@@ -628,16 +629,12 @@ static int radeon_acpi_vfct_match(struct radeon_device *rdev,
vhdr->PCIFunction != PCI_FUNC(rdev->pdev->devfn))
return -ENODEV;
- /* Exact bus number match - preferred */
- if (vhdr->PCIBus == rdev->pdev->bus->number)
- return 0;
+ if (bridge && bridge->fw_sec_bus_valid)
+ initial_bus = bridge->fw_sec_busnr;
+ else
+ initial_bus = rdev->pdev->bus->number;
- /* Bus mismatch but device identity matches (PCI renumbering case) */
- dev_notice(&rdev->pdev->dev,
- "VFCT bus number mismatch: table %u != runtime %u, matching by device identity (vendor 0x%04x device 0x%04x)\n",
- vhdr->PCIBus, rdev->pdev->bus->number,
- rdev->pdev->vendor, rdev->pdev->device);
- return 0;
+ return vhdr->PCIBus == initial_bus ? 0 : -ENODEV;
}
static bool radeon_acpi_vfct_bios(struct radeon_device *rdev)
--
2.43.0
^ permalink raw reply related [flat|nested] 7+ messages in thread