[PATCH v2 0/3] Fix amdgpu detection of pci=realloc

[PATCH v2 0/3] 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>
---
Changes in v2:
- pci_alloc_dev(NULL) remains safe.
- For buses behind a reassigned bridge, the PCI core now saves the firmware secondary bus
  number before clearing the bridge configuration and carries it into the newly allocated bus.
  Devices discovered there inherit that original number.
- Add changes for radeon too.
- Link to v1: https://patch.msgid.link/20261019-vfct-regression-v1-0-5a63ddd378dd@amd.com

---
Mario Limonciello (3):
      PCI: Preserve the initial bus number in pci_dev
      drm/amdgpu: Match VFCT using initial PCI bus number
      drm/radeon: Match VFCT using initial PCI bus number

 drivers/gpu/drm/amd/amdgpu/amdgpu_bios.c | 17 +++--------------
 drivers/gpu/drm/radeon/radeon_bios.c     | 17 +++--------------
 drivers/pci/probe.c                      |  9 +++++++++
 include/linux/pci.h                      |  3 +++
 4 files changed, 18 insertions(+), 28 deletions(-)
---
base-commit: c03c1a14507dfaf8b856c2608f9ac216021fc222
change-id: 20261019-vfct-regression-2142fc52852a

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

[PATCH v2 1/3] PCI: Preserve the initial bus number in pci_dev

[Mario Limonciello]

Bridges that need bus reassignment are scanned in two passes. Save
the firmware secondary bus number during the first pass, before the
bridge is disabled, and carry it to the bus created in the second
pass. Initialize pci_dev from this preserved bus number so drivers
can match firmware records after PCI bus renumbering.

Handle pci_alloc_dev(NULL) as well; some in-tree callers use it to
allocate a standalone pci_dev.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/pci/probe.c | 9 +++++++++
 include/linux/pci.h | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 27008e2ea5afc..4ece4b70cdc15 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1012,6 +1012,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
 	bus->sysdata = bridge->sysdata;
 	bus->ops = bridge->ops;
 	bus->number = bus->busn_res.start = bridge->busnr;
+	bus->initial_bus_number = bus->number;
 #ifdef CONFIG_PCI_DOMAINS_GENERIC
 	if (bridge->domain_nr == PCI_DOMAIN_NR_NOT_SET)
 		bus->domain_nr = pci_bus_find_domain_nr(bus, parent);
@@ -1232,6 +1233,7 @@ static struct pci_bus *pci_alloc_child_bus(struct pci_bus *parent,
 
 	/* Set up the primary, secondary and subordinate bus numbers */
 	child->number = child->busn_res.start = busnr;
+	child->initial_bus_number = busnr;
 	child->primary = parent->busn_res.start;
 	child->busn_res.end = 0xff;
 
@@ -1470,6 +1472,7 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 			child = pci_add_new_bus(bus, dev, secondary);
 			if (!child)
 				goto out;
+			child->initial_bus_number = secondary;
 			child->primary = primary;
 			pci_bus_insert_busn_res(child, secondary, subordinate);
 			child->bridge_ctl = bctl;
@@ -1491,6 +1494,8 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 		 * do in the second pass.
 		 */
 		if (!pass) {
+			if (!dev->initial_secondary_bus_number)
+				dev->initial_secondary_bus_number = secondary;
 			if (pcibios_assign_all_busses() || broken)
 
 				/*
@@ -1526,6 +1531,9 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
 			child = pci_add_new_bus(bus, dev, next_busnr);
 			if (!child)
 				goto out;
+			if (dev->initial_secondary_bus_number)
+				child->initial_bus_number =
+					dev->initial_secondary_bus_number;
 			pci_bus_insert_busn_res(child, next_busnr,
 						bus->busn_res.end);
 		}
@@ -2508,6 +2516,7 @@ 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 ? bus->initial_bus_number : 0;
 	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..f6b377dcf7a14 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 */
+	u8		initial_bus_number;	/* Bus number when device was discovered */
+	u8		initial_secondary_bus_number;	/* Bus number behind this bridge */
 	unsigned short	vendor;
 	unsigned short	device;
 	unsigned short	subsystem_vendor;
@@ -724,6 +726,7 @@ struct pci_bus {
 	struct proc_dir_entry *procdir;	/* Directory entry in /proc/bus/pci */
 
 	unsigned char	number;		/* Bus number */
+	unsigned char	initial_bus_number;	/* Bus number before reassignment */
 	unsigned char	primary;	/* Number of primary bridge */
 	unsigned char	max_bus_speed;	/* enum pci_bus_speed */
 	unsigned char	cur_bus_speed;	/* enum pci_bus_speed */

-- 
2.43.0

[PATCH v2 2/3] 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
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 | 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

[PATCH v2 3/3] drm/radeon: 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
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 | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_bios.c b/drivers/gpu/drm/radeon/radeon_bios.c
index 1da6bf1c17ff3..88989c93757b1 100644
--- a/drivers/gpu/drm/radeon/radeon_bios.c
+++ b/drivers/gpu/drm/radeon/radeon_bios.c
@@ -609,10 +609,8 @@ 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
  */
@@ -628,16 +626,7 @@ 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;
-
-	/* 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 == rdev->pdev->initial_bus_number ? 0 : -ENODEV;
 }
 
 static bool radeon_acpi_vfct_bios(struct radeon_device *rdev)

-- 
2.43.0