On our Marvell OCTEON CN96XX board, we observed the following panic on the latest kernel: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000080 Mem abort info: ESR = 0x0000000096000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault Data abort info: ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [0000000000000080] user address but active_mm is swapper Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP Modules linked in: CPU: 9 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.13.0-rc7-00149-g9bffa1ad25b8 #1 Hardware name: Marvell OcteonTX CN96XX board (DT) pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : of_pci_add_properties+0x278/0x4c8 lr : of_pci_add_properties+0x258/0x4c8 sp : ffff8000822ef9b0 x29: ffff8000822ef9b0 x28: ffff000106dd8000 x27: ffff800081bc3b30 x26: ffff800081540118 x25: ffff8000813d2be0 x24: 0000000000000000 x23: ffff00010528a800 x22: ffff000107c50000 x21: ffff0001039c2630 x20: ffff0001039c2630 x19: 0000000000000000 x18: ffffffffffffffff x17: 00000000a49c1b85 x16: 0000000084c07b58 x15: ffff000103a10f98 x14: ffffffffffffffff x13: ffff000103a10f96 x12: 0000000000000003 x11: 0101010101010101 x10: 000000000000002c x9 : ffff800080ca7acc x8 : ffff0001038fd900 x7 : 0000000000000000 x6 : 0000000000696370 x5 : 0000000000000000 x4 : 0000000000000002 x3 : ffff8000822efa40 x2 : ffff800081341000 x1 : ffff000107c50000 x0 : 0000000000000000 Call trace: of_pci_add_properties+0x278/0x4c8 (P) of_pci_make_dev_node+0xe0/0x158 pci_bus_add_device+0x158/0x210 pci_bus_add_devices+0x40/0x98 pci_host_probe+0x94/0x118 pci_host_common_probe+0x120/0x1a0 platform_probe+0x70/0xf0 really_probe+0xb4/0x2a8 __driver_probe_device+0x80/0x140 driver_probe_device+0x48/0x170 __driver_attach+0x9c/0x1b0 bus_for_each_dev+0x7c/0xe8 driver_attach+0x2c/0x40 bus_add_driver+0xec/0x218 driver_register+0x68/0x138 __platform_driver_register+0x2c/0x40 gen_pci_driver_init+0x24/0x38 do_one_initcall+0x4c/0x278 kernel_init_freeable+0x1f4/0x3d0 kernel_init+0x28/0x1f0 ret_from_fork+0x10/0x20 Code: aa1603e1 f0005522 d2800044 91000042 (f94040a0)
This regression was introduced by commit 7246a4520b4b ("PCI: Use preserve_config in place of pci_flags"). On our board, the 002:00:07.0 bridge is misconfigured by the bootloader. Both its secondary and subordinate bus numbers are initialized to 0, while its fixed secondary bus number is set to 8. However, bus number 8 is also assigned to another bridge (0002:00:0f.0). Although this is a bootloader issue, before the change in commit 7246a4520b4b, the PCI_REASSIGN_ALL_BUS flag was set by default when PCI_PROBE_ONLY was enabled, ensuing that all the bus number for these bridges were reassigned, avoiding any conflicts.
After the change introduced in commit 7246a4520b4b, the bus numbers assigned by the bootloader are reused by all other bridges, except the misconfigured 002:00:07.0 bridge. The kernel attempt to reconfigure 002:00:07.0 by reusing the fixed secondary bus number 8 assigned by bootloader. However, since a pci_bus has already been allocated for bus 8 due to the probe of 0002:00:0f.0, no new pci_bus allocated for 002:00:07.0. This results in a pci bridge device without a pci_bus attached (pdev->subordinate == NULL). Consequently, accessing pdev->subordinate in of_pci_prop_bus_range() leads to a NULL pointer dereference.
To summarize, we need to restore the PCI_REASSIGN_ALL_BUS flag when PCI_PROBE_ONLY is enabled in order to work around issue like the one described above.
Cc: stable@vger.kernel.org Fixes: 7246a4520b4b ("PCI: Use preserve_config in place of pci_flags") Signed-off-by: Bo Sun Bo.Sun.CN@windriver.com --- drivers/pci/controller/pci-host-common.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c index cf5f59a745b3..615923acbc3e 100644 --- a/drivers/pci/controller/pci-host-common.c +++ b/drivers/pci/controller/pci-host-common.c @@ -73,6 +73,10 @@ int pci_host_common_probe(struct platform_device *pdev) if (IS_ERR(cfg)) return PTR_ERR(cfg);
+ /* Do not reassign resources if probe only */ + if (!pci_has_flag(PCI_PROBE_ONLY)) + pci_add_flags(PCI_REASSIGN_ALL_BUS); + bridge->sysdata = cfg; bridge->ops = (struct pci_ops *)&ops->pci_ops; bridge->msi_domain = true;
On 1/17/25 16:24, Bo Sun wrote:
On our Marvell OCTEON CN96XX board, we observed the following panic on the latest kernel: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000080 Mem abort info: ESR = 0x0000000096000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault Data abort info: ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [0000000000000080] user address but active_mm is swapper Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP Modules linked in: CPU: 9 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.13.0-rc7-00149-g9bffa1ad25b8 #1 Hardware name: Marvell OcteonTX CN96XX board (DT) pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : of_pci_add_properties+0x278/0x4c8 lr : of_pci_add_properties+0x258/0x4c8 sp : ffff8000822ef9b0 x29: ffff8000822ef9b0 x28: ffff000106dd8000 x27: ffff800081bc3b30 x26: ffff800081540118 x25: ffff8000813d2be0 x24: 0000000000000000 x23: ffff00010528a800 x22: ffff000107c50000 x21: ffff0001039c2630 x20: ffff0001039c2630 x19: 0000000000000000 x18: ffffffffffffffff x17: 00000000a49c1b85 x16: 0000000084c07b58 x15: ffff000103a10f98 x14: ffffffffffffffff x13: ffff000103a10f96 x12: 0000000000000003 x11: 0101010101010101 x10: 000000000000002c x9 : ffff800080ca7acc x8 : ffff0001038fd900 x7 : 0000000000000000 x6 : 0000000000696370 x5 : 0000000000000000 x4 : 0000000000000002 x3 : ffff8000822efa40 x2 : ffff800081341000 x1 : ffff000107c50000 x0 : 0000000000000000 Call trace: of_pci_add_properties+0x278/0x4c8 (P) of_pci_make_dev_node+0xe0/0x158 pci_bus_add_device+0x158/0x210 pci_bus_add_devices+0x40/0x98 pci_host_probe+0x94/0x118 pci_host_common_probe+0x120/0x1a0 platform_probe+0x70/0xf0 really_probe+0xb4/0x2a8 __driver_probe_device+0x80/0x140 driver_probe_device+0x48/0x170 __driver_attach+0x9c/0x1b0 bus_for_each_dev+0x7c/0xe8 driver_attach+0x2c/0x40 bus_add_driver+0xec/0x218 driver_register+0x68/0x138 __platform_driver_register+0x2c/0x40 gen_pci_driver_init+0x24/0x38 do_one_initcall+0x4c/0x278 kernel_init_freeable+0x1f4/0x3d0 kernel_init+0x28/0x1f0 ret_from_fork+0x10/0x20 Code: aa1603e1 f0005522 d2800044 91000042 (f94040a0)
This regression was introduced by commit 7246a4520b4b ("PCI: Use preserve_config in place of pci_flags"). On our board, the 002:00:07.0 bridge is misconfigured by the bootloader. Both its secondary and subordinate bus numbers are initialized to 0, while its fixed secondary bus number is set to 8. However, bus number 8 is also assigned to another bridge (0002:00:0f.0). Although this is a bootloader issue, before the change in commit 7246a4520b4b, the PCI_REASSIGN_ALL_BUS flag was set by default when PCI_PROBE_ONLY was enabled, ensuing that all the bus number for these bridges were reassigned, avoiding any conflicts.
After the change introduced in commit 7246a4520b4b, the bus numbers assigned by the bootloader are reused by all other bridges, except the misconfigured 002:00:07.0 bridge. The kernel attempt to reconfigure 002:00:07.0 by reusing the fixed secondary bus number 8 assigned by bootloader. However, since a pci_bus has already been allocated for bus 8 due to the probe of 0002:00:0f.0, no new pci_bus allocated for 002:00:07.0. This results in a pci bridge device without a pci_bus attached (pdev->subordinate == NULL). Consequently, accessing pdev->subordinate in of_pci_prop_bus_range() leads to a NULL pointer dereference.
To summarize, we need to restore the PCI_REASSIGN_ALL_BUS flag when PCI_PROBE_ONLY is enabled in order to work around issue like the one described above.
Cc: stable@vger.kernel.org Fixes: 7246a4520b4b ("PCI: Use preserve_config in place of pci_flags") Signed-off-by: Bo Sun Bo.Sun.CN@windriver.com
drivers/pci/controller/pci-host-common.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c index cf5f59a745b3..615923acbc3e 100644 --- a/drivers/pci/controller/pci-host-common.c +++ b/drivers/pci/controller/pci-host-common.c @@ -73,6 +73,10 @@ int pci_host_common_probe(struct platform_device *pdev) if (IS_ERR(cfg)) return PTR_ERR(cfg);
- /* Do not reassign resources if probe only */
- if (!pci_has_flag(PCI_PROBE_ONLY))
pci_add_flags(PCI_REASSIGN_ALL_BUS);- bridge->sysdata = cfg; bridge->ops = (struct pci_ops *)&ops->pci_ops; bridge->msi_domain = true;
Dear All,
I hope this message finds you well.
I’m writing to follow up on this patch. I understand the community may be busy with numerous tasks, but I wanted to check if there has been any feedback or progress on reviewing the patch. As the issue remains unresolved, I just wanted to ensure my submission was received and is being considered.
Thank you for your time and consideration.
Best regards, Bo
On Fri, Jan 17, 2025 at 04:24:14PM +0800, Bo Sun wrote:
On our Marvell OCTEON CN96XX board, we observed the following panic on the latest kernel: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000080 Mem abort info: ESR = 0x0000000096000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault Data abort info: ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [0000000000000080] user address but active_mm is swapper Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP Modules linked in: CPU: 9 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.13.0-rc7-00149-g9bffa1ad25b8 #1 Hardware name: Marvell OcteonTX CN96XX board (DT) pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : of_pci_add_properties+0x278/0x4c8 lr : of_pci_add_properties+0x258/0x4c8 sp : ffff8000822ef9b0 x29: ffff8000822ef9b0 x28: ffff000106dd8000 x27: ffff800081bc3b30 x26: ffff800081540118 x25: ffff8000813d2be0 x24: 0000000000000000 x23: ffff00010528a800 x22: ffff000107c50000 x21: ffff0001039c2630 x20: ffff0001039c2630 x19: 0000000000000000 x18: ffffffffffffffff x17: 00000000a49c1b85 x16: 0000000084c07b58 x15: ffff000103a10f98 x14: ffffffffffffffff x13: ffff000103a10f96 x12: 0000000000000003 x11: 0101010101010101 x10: 000000000000002c x9 : ffff800080ca7acc x8 : ffff0001038fd900 x7 : 0000000000000000 x6 : 0000000000696370 x5 : 0000000000000000 x4 : 0000000000000002 x3 : ffff8000822efa40 x2 : ffff800081341000 x1 : ffff000107c50000 x0 : 0000000000000000 Call trace: of_pci_add_properties+0x278/0x4c8 (P) of_pci_make_dev_node+0xe0/0x158 pci_bus_add_device+0x158/0x210 pci_bus_add_devices+0x40/0x98 pci_host_probe+0x94/0x118 pci_host_common_probe+0x120/0x1a0 platform_probe+0x70/0xf0 really_probe+0xb4/0x2a8 __driver_probe_device+0x80/0x140 driver_probe_device+0x48/0x170 __driver_attach+0x9c/0x1b0 bus_for_each_dev+0x7c/0xe8 driver_attach+0x2c/0x40 bus_add_driver+0xec/0x218 driver_register+0x68/0x138 __platform_driver_register+0x2c/0x40 gen_pci_driver_init+0x24/0x38 do_one_initcall+0x4c/0x278 kernel_init_freeable+0x1f4/0x3d0 kernel_init+0x28/0x1f0 ret_from_fork+0x10/0x20 Code: aa1603e1 f0005522 d2800044 91000042 (f94040a0)
This regression was introduced by commit 7246a4520b4b ("PCI: Use preserve_config in place of pci_flags"). On our board, the 002:00:07.0 bridge is misconfigured by the bootloader. Both its secondary and subordinate bus numbers are initialized to 0, while its fixed secondary bus number is set to 8.
What do you mean by 'fixed secondary bus number'?
However, bus number 8 is also assigned to another bridge (0002:00:0f.0). Although this is a bootloader issue, before the change in commit 7246a4520b4b, the PCI_REASSIGN_ALL_BUS flag was set by default when PCI_PROBE_ONLY was enabled, ensuing that all the bus number for these bridges were reassigned, avoiding any conflicts.
Isn't the opposite? PCI_REASSIGN_ALL_BUS was only added if the PCI_PROBE_ONLY flag was not set:
/* Do not reassign resources if probe only */ if (!pci_has_flag(PCI_PROBE_ONLY)) pci_add_flags(PCI_REASSIGN_ALL_BUS);
After the change introduced in commit 7246a4520b4b, the bus numbers assigned by the bootloader are reused by all other bridges, except the misconfigured 002:00:07.0 bridge. The kernel attempt to reconfigure 002:00:07.0 by reusing the fixed secondary bus number 8 assigned by bootloader. However, since a pci_bus has already been allocated for bus 8 due to the probe of 0002:00:0f.0, no new pci_bus allocated for 002:00:07.0.
How come 0002:00:0f.0 is enumerated before 0002:00:07.0 in a depth first manner?
This results in a pci bridge device without a pci_bus attached (pdev->subordinate == NULL). Consequently, accessing pdev->subordinate in of_pci_prop_bus_range() leads to a NULL pointer dereference.
Looks like it is a bug to let a bridge proceed without 'pdev->subordinate' assigned.
- Mani
On 2/10/25 18:37, Manivannan Sadhasivam wrote:
CAUTION: This email comes from a non Wind River email account! Do not click links or open attachments unless you recognize the sender and know the content is safe.
On Fri, Jan 17, 2025 at 04:24:14PM +0800, Bo Sun wrote:
On our Marvell OCTEON CN96XX board, we observed the following panic on the latest kernel: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000080 Mem abort info: ESR = 0x0000000096000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault Data abort info: ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [0000000000000080] user address but active_mm is swapper Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP Modules linked in: CPU: 9 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.13.0-rc7-00149-g9bffa1ad25b8 #1 Hardware name: Marvell OcteonTX CN96XX board (DT) pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : of_pci_add_properties+0x278/0x4c8 lr : of_pci_add_properties+0x258/0x4c8 sp : ffff8000822ef9b0 x29: ffff8000822ef9b0 x28: ffff000106dd8000 x27: ffff800081bc3b30 x26: ffff800081540118 x25: ffff8000813d2be0 x24: 0000000000000000 x23: ffff00010528a800 x22: ffff000107c50000 x21: ffff0001039c2630 x20: ffff0001039c2630 x19: 0000000000000000 x18: ffffffffffffffff x17: 00000000a49c1b85 x16: 0000000084c07b58 x15: ffff000103a10f98 x14: ffffffffffffffff x13: ffff000103a10f96 x12: 0000000000000003 x11: 0101010101010101 x10: 000000000000002c x9 : ffff800080ca7acc x8 : ffff0001038fd900 x7 : 0000000000000000 x6 : 0000000000696370 x5 : 0000000000000000 x4 : 0000000000000002 x3 : ffff8000822efa40 x2 : ffff800081341000 x1 : ffff000107c50000 x0 : 0000000000000000 Call trace: of_pci_add_properties+0x278/0x4c8 (P) of_pci_make_dev_node+0xe0/0x158 pci_bus_add_device+0x158/0x210 pci_bus_add_devices+0x40/0x98 pci_host_probe+0x94/0x118 pci_host_common_probe+0x120/0x1a0 platform_probe+0x70/0xf0 really_probe+0xb4/0x2a8 __driver_probe_device+0x80/0x140 driver_probe_device+0x48/0x170 __driver_attach+0x9c/0x1b0 bus_for_each_dev+0x7c/0xe8 driver_attach+0x2c/0x40 bus_add_driver+0xec/0x218 driver_register+0x68/0x138 __platform_driver_register+0x2c/0x40 gen_pci_driver_init+0x24/0x38 do_one_initcall+0x4c/0x278 kernel_init_freeable+0x1f4/0x3d0 kernel_init+0x28/0x1f0 ret_from_fork+0x10/0x20 Code: aa1603e1 f0005522 d2800044 91000042 (f94040a0)
This regression was introduced by commit 7246a4520b4b ("PCI: Use preserve_config in place of pci_flags"). On our board, the 002:00:07.0 bridge is misconfigured by the bootloader. Both its secondary and subordinate bus numbers are initialized to 0, while its fixed secondary bus number is set to 8.
What do you mean by 'fixed secondary bus number'?
The 'fixed secondary bus number' refers to the value returned by the function pci_ea_fixed_busnrs(), which reads the fixed Secondary and Subordinate bus numbers from the EA (Extended Attributes) capability, if present. In the code at drivers/pci/probe.c, line 1439, we have the following:
/* Read bus numbers from EA Capability (if present) */ fixed_buses = pci_ea_fixed_busnrs(dev, &fixed_sec, &fixed_sub); if (fixed_buses) next_busnr = fixed_sec; else next_busnr = max + 1;
However, bus number 8 is also assigned to another bridge (0002:00:0f.0). Although this is a bootloader issue, before the change in commit 7246a4520b4b, the PCI_REASSIGN_ALL_BUS flag was set by default when PCI_PROBE_ONLY was enabled, ensuing that all the bus number for these bridges were reassigned, avoiding any conflicts.
Isn't the opposite? PCI_REASSIGN_ALL_BUS was only added if the PCI_PROBE_ONLY flag was not set:
/* Do not reassign resources if probe only */ if (!pci_has_flag(PCI_PROBE_ONLY)) pci_add_flags(PCI_REASSIGN_ALL_BUS);
Yes, you are correct. It’s a typo; it should be "when PCI_PROBE_ONLY was not enabled." I will fix this in v2.
After the change introduced in commit 7246a4520b4b, the bus numbers assigned by the bootloader are reused by all other bridges, except the misconfigured 002:00:07.0 bridge. The kernel attempt to reconfigure 002:00:07.0 by reusing the fixed secondary bus number 8 assigned by bootloader. However, since a pci_bus has already been allocated for bus 8 due to the probe of 0002:00:0f.0, no new pci_bus allocated for 002:00:07.0.
How come 0002:00:0f.0 is enumerated before 0002:00:07.0 in a depth first manner?
The device 0002:00:07.0 is actually enumerated before 0002:00:0f.0, but it appears misconfigured. The kernel attempts to reconfigure it during initialization, which is where the issue arises.
This results in a pci bridge device without a pci_bus attached (pdev->subordinate == NULL). Consequently, accessing pdev->subordinate in of_pci_prop_bus_range() leads to a NULL pointer dereference.
Looks like it is a bug to let a bridge proceed without 'pdev->subordinate' assigned.
- Mani
Yes, you are correct.
-- மணிவண்ணன் சதாசிவம்
On Wed, Feb 12, 2025 at 03:07:56PM +0800, Bo Sun wrote:
On 2/10/25 18:37, Manivannan Sadhasivam wrote:
CAUTION: This email comes from a non Wind River email account! Do not click links or open attachments unless you recognize the sender and know the content is safe.
On Fri, Jan 17, 2025 at 04:24:14PM +0800, Bo Sun wrote:
On our Marvell OCTEON CN96XX board, we observed the following panic on the latest kernel: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000080 Mem abort info: ESR = 0x0000000096000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault Data abort info: ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [0000000000000080] user address but active_mm is swapper Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP Modules linked in: CPU: 9 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.13.0-rc7-00149-g9bffa1ad25b8 #1 Hardware name: Marvell OcteonTX CN96XX board (DT) pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : of_pci_add_properties+0x278/0x4c8 lr : of_pci_add_properties+0x258/0x4c8 sp : ffff8000822ef9b0 x29: ffff8000822ef9b0 x28: ffff000106dd8000 x27: ffff800081bc3b30 x26: ffff800081540118 x25: ffff8000813d2be0 x24: 0000000000000000 x23: ffff00010528a800 x22: ffff000107c50000 x21: ffff0001039c2630 x20: ffff0001039c2630 x19: 0000000000000000 x18: ffffffffffffffff x17: 00000000a49c1b85 x16: 0000000084c07b58 x15: ffff000103a10f98 x14: ffffffffffffffff x13: ffff000103a10f96 x12: 0000000000000003 x11: 0101010101010101 x10: 000000000000002c x9 : ffff800080ca7acc x8 : ffff0001038fd900 x7 : 0000000000000000 x6 : 0000000000696370 x5 : 0000000000000000 x4 : 0000000000000002 x3 : ffff8000822efa40 x2 : ffff800081341000 x1 : ffff000107c50000 x0 : 0000000000000000 Call trace: of_pci_add_properties+0x278/0x4c8 (P) of_pci_make_dev_node+0xe0/0x158 pci_bus_add_device+0x158/0x210 pci_bus_add_devices+0x40/0x98 pci_host_probe+0x94/0x118 pci_host_common_probe+0x120/0x1a0 platform_probe+0x70/0xf0 really_probe+0xb4/0x2a8 __driver_probe_device+0x80/0x140 driver_probe_device+0x48/0x170 __driver_attach+0x9c/0x1b0 bus_for_each_dev+0x7c/0xe8 driver_attach+0x2c/0x40 bus_add_driver+0xec/0x218 driver_register+0x68/0x138 __platform_driver_register+0x2c/0x40 gen_pci_driver_init+0x24/0x38 do_one_initcall+0x4c/0x278 kernel_init_freeable+0x1f4/0x3d0 kernel_init+0x28/0x1f0 ret_from_fork+0x10/0x20 Code: aa1603e1 f0005522 d2800044 91000042 (f94040a0)
This regression was introduced by commit 7246a4520b4b ("PCI: Use preserve_config in place of pci_flags"). On our board, the 002:00:07.0 bridge is misconfigured by the bootloader. Both its secondary and subordinate bus numbers are initialized to 0, while its fixed secondary bus number is set to 8.
What do you mean by 'fixed secondary bus number'?
The 'fixed secondary bus number' refers to the value returned by the function pci_ea_fixed_busnrs(), which reads the fixed Secondary and Subordinate bus numbers from the EA (Extended Attributes) capability, if present.
Thanks! It'd be good to mention the EA capability.
In the code at drivers/pci/probe.c, line 1439, we have the following:
/* Read bus numbers from EA Capability (if present) */ fixed_buses = pci_ea_fixed_busnrs(dev, &fixed_sec, &fixed_sub); if (fixed_buses) next_busnr = fixed_sec; else next_busnr = max + 1;However, bus number 8 is also assigned to another bridge (0002:00:0f.0). Although this is a bootloader issue, before the change in commit 7246a4520b4b, the PCI_REASSIGN_ALL_BUS flag was set by default when PCI_PROBE_ONLY was enabled, ensuing that all the bus number for these bridges were reassigned, avoiding any conflicts.
Isn't the opposite? PCI_REASSIGN_ALL_BUS was only added if the PCI_PROBE_ONLY flag was not set:
/* Do not reassign resources if probe only */ if (!pci_has_flag(PCI_PROBE_ONLY)) pci_add_flags(PCI_REASSIGN_ALL_BUS);Yes, you are correct. It’s a typo; it should be "when PCI_PROBE_ONLY was not enabled." I will fix this in v2.
After the change introduced in commit 7246a4520b4b, the bus numbers assigned by the bootloader are reused by all other bridges, except the misconfigured 002:00:07.0 bridge. The kernel attempt to reconfigure 002:00:07.0 by reusing the fixed secondary bus number 8 assigned by bootloader. However, since a pci_bus has already been allocated for bus 8 due to the probe of 0002:00:0f.0, no new pci_bus allocated for 002:00:07.0.
How come 0002:00:0f.0 is enumerated before 0002:00:07.0 in a depth first manner?
The device 0002:00:07.0 is actually enumerated before 0002:00:0f.0, but it appears misconfigured. The kernel attempts to reconfigure it during initialization, which is where the issue arises.
Ok, thanks for the clarification. I think the bug is in this part of the code: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/driv...
It just reuses the fixed bus number even if the bus already exists, which is wrong. I think this should be fixed by evaluating the bus number read from EA capability as below:
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index b6536ed599c3..097e2a01faae 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -1438,10 +1438,21 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
/* Read bus numbers from EA Capability (if present) */ fixed_buses = pci_ea_fixed_busnrs(dev, &fixed_sec, &fixed_sub); - if (fixed_buses) - next_busnr = fixed_sec; - else + if (fixed_buses) { + /* + * If the fixed bus number is already taken, use the + * next available bus number. This can happen if the + * bootloader has assigned a wrong bus number in EA + * capability of the bridge. + */ + child = pci_find_bus(pci_domain_nr(bus), fixed_sec); + if (child) + next_busnr = max + 1; + else + next_busnr = fixed_sec; + } else { next_busnr = max + 1; + }
/* * Prevent assigning a bus number that already exists.
- Mani
linux-stable-mirror@lists.linaro.org
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Bo Sun -
Manivannan Sadhasivam -
Manivannan Sadhasivam