riscv: Fix PCI warning by enabling PCI_MSI_ARCH_FALLBACKS

RFC PATCH In review Alexandre Ghiti 7 participants 12 messages Dec 13, 2024 – Apr 22

Subsystems (5)

Stable branch PCI RISC-V LoongArch +1 more subsystems

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Alexandre Ghiti

author

2024-12-13 11:57 UTC #0 lore raw

RFC PATCH 1/1 riscv: Fix PCI warning by enabling PCI_MSI_ARCH_FALLBACKS

When the interrupt controller is not using the IMSIC and ACPI is enabled, the following warning appears:

[    0.866401] WARNING: CPU: 1 PID: 1 at drivers/pci/msi/msi.h:121 pci_msi_setup_msi_irqs+0x2c/0x32
[    0.867071] Modules linked in:
[    0.867389] CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.13.0-rc2-00001-g795582ce7e24-dirty #44
[    0.867538] Hardware name: QEMU QEMU Virtual Machine, BIOS
[    0.867672] epc : pci_msi_setup_msi_irqs+0x2c/0x32
[    0.867738]  ra : __pci_enable_msix_range+0x30c/0x596
[    0.867783] epc : ffffffff8050af80 ra : ffffffff8050a66e sp : ff20000000023750
[    0.867809]  gp : ffffffff815153b0 tp : ff60000080108000 t0 : ff60000081109600
[    0.867833]  t1 : 0000000000000228 t2 : 0000000000000004 s0 : ff20000000023860
[    0.867857]  s1 : ff60000080de1000 a0 : ff60000080de1000 a1 : 0000000000000005
[    0.867880]  a2 : 0000000000000011 a3 : 0000000000000000 a4 : 0000000000000000
[    0.867902]  a5 : 0000000000000000 a6 : ff600000806368f0 a7 : fffffffffffffff0
[    0.867925]  s2 : 0000000000000005 s3 : ffffffffffffffff s4 : 0000000000000000
[    0.867948]  s5 : ff60000080de10c0 s6 : 0000000000000005 s7 : 0000000000000005
[    0.867970]  s8 : ff20000000023a08 s9 : ff600000811093c0 s10: 000000000000002c
[    0.867993]  s11: ff60000081109410 t3 : 0000000000000001 t4 : ff600000803a2878
[    0.868014]  t5 : 0000000000000004 t6 : ff60000080357450
[    0.868036] status: 0000000200000120 badaddr: ffffffff8050af80 cause: 0000000000000003
[    0.868186] [<ffffffff8050af80>] pci_msi_setup_msi_irqs+0x2c/0x32
[    0.868339] [<ffffffff80509172>] pci_alloc_irq_vectors_affinity+0xb8/0xe2
[    0.868362] [<ffffffff8059d62c>] vp_find_vqs_msix+0x12a/0x370
[    0.868385] [<ffffffff8059d8a0>] vp_find_vqs+0x2e/0x1de
[    0.868402] [<ffffffff8059bd80>] vp_modern_find_vqs+0x12/0x4e
[    0.868425] [<ffffffff80624a50>] init_vq+0x2b4/0x336
[    0.868448] [<ffffffff80624c36>] virtblk_probe+0xd4/0x90e
[    0.868469] [<ffffffff80594e02>] virtio_dev_probe+0x14a/0x1e6
[    0.868488] [<ffffffff805fe04c>] really_probe+0x86/0x234
[    0.868509] [<ffffffff805fe256>] __driver_probe_device+0x5c/0xda
[    0.868529] [<ffffffff805fe392>] driver_probe_device+0x2c/0xb2
[    0.868549] [<ffffffff805fe512>] __driver_attach+0x6c/0x11a
[    0.868569] [<ffffffff805fc17e>] bus_for_each_dev+0x60/0xae
[    0.868588] [<ffffffff805fda7c>] driver_attach+0x1a/0x22
[    0.868607] [<ffffffff805fd398>] bus_add_driver+0xce/0x1d6
[    0.868627] [<ffffffff805ff0b2>] driver_register+0x3e/0xd8
[    0.868647] [<ffffffff80594614>] __register_virtio_driver+0x1e/0x2c
[    0.868694] [<ffffffff80a31b82>] virtio_blk_init+0x6a/0x9e
[    0.868733] [<ffffffff8000f128>] do_one_initcall+0x58/0x194
[    0.868755] [<ffffffff80a011b0>] kernel_init_freeable+0x224/0x28e
[    0.868775] [<ffffffff809e4e48>] kernel_init+0x1e/0x13a
[    0.868795] [<ffffffff809ed952>] ret_from_fork+0xe/0x18

So enable PCI_MSI_ARCH_FALLBACKS to get rid of this.

Signed-off-by Alexandre Ghiti <[email protected]>

---

This is an RFC as I'm really not sure this is the right fix, Anup/Sunil/Thomas if you have any idea, please step in! Thanks

 arch/riscv/Kconfig | 1 +
 1 file changed, 1 insertion(+)

arch/riscv/Kconfig +1 -0

index d4a7ca0388c0..40d51feac2bb 100644
@@ -199,6 +199,7 @@ config RISCV
 	select PCI_DOMAINS_GENERIC if PCI
 	select PCI_ECAM if (ACPI && PCI)
 	select PCI_MSI if PCI
+	select PCI_MSI_ARCH_FALLBACKS if PCI
 	select RISCV_ALTERNATIVE if !XIP_KERNEL
 	select RISCV_APLIC
 	select RISCV_IMSIC

Signature · 1 line

2.39.2

Thomas Gleixner

2024-12-13 13:12 UTC #1 lore raw

Quoted 9 lines · Alexandre Ghiti

When the interrupt controller is not using the IMSIC and ACPI is enabled, the following warning appears:

[    0.866401] WARNING: CPU: 1 PID: 1 at drivers/pci/msi/msi.h:121 pci_msi_setup_msi_irqs+0x2c/0x32
[    0.867071] Modules linked in:
[    0.867389] CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.13.0-rc2-00001-g795582ce7e24-dirty #44
[    0.867538] Hardware name: QEMU QEMU Virtual Machine, BIOS
[    0.867672] epc : pci_msi_setup_msi_irqs+0x2c/0x32
[    0.867738]  ra : __pci_enable_msix_range+0x30c/0x596

Removing a ton of badly formatted stack trace:

https://www.kernel.org/doc/html/latest/process/submitting-patches.html#backtraces-in-commit-messages

Quoted 2 lines

So enable PCI_MSI_ARCH_FALLBACKS to get rid of this.

No. PCI_MSI_ARCH_FALLBACKS is really only meant for architectures which implement the legacy fallbacks and not to paper over the underlying logic bug in the pci/msi code. Of course the loongson folks ran into the same problem two years ago and went for the sloppy fix without talking to anyone...

Thanks for bringing it up instead of silently slapping it into the RISCV tree !

The uncompiled patch below should fix this for real.

Thanks,

tglx
---

arch/loongarch/Kconfig +0 -1

@@ -185,7 +185,6 @@ config LOONGARCH
 	select PCI_DOMAINS_GENERIC
 	select PCI_ECAM if ACPI
 	select PCI_LOONGSON
-	select PCI_MSI_ARCH_FALLBACKS
 	select PCI_QUIRKS
 	select PERF_USE_VMALLOC
 	select RTC_LIB

drivers/pci/msi/irqdomain.c +5 -2

@@ -350,8 +350,11 @@ bool pci_msi_domain_supports(struct pci_
 
 	domain = dev_get_msi_domain(&pdev->dev);
 
-	if (!domain || !irq_domain_is_hierarchy(domain))
-		return mode == ALLOW_LEGACY;
+	if (!domain || !irq_domain_is_hierarchy(domain)) {
+		if (IS_ENABLED(CONFIG_PCI_MSI_ARCH_FALLBACKS))
+			return mode == ALLOW_LEGACY;
+		return false;
+	}
 
 	if (!irq_domain_is_msi_parent(domain)) {
 		/*

drivers/pci/msi/msi.c +4 -0

@@ -442,6 +442,10 @@ int __pci_enable_msi_range(struct pci_de
 	if (nvec > maxvec)
 		nvec = maxvec;
 
+	/* Test for the availability of MSI support */
+	if (!pci_msi_domain_supports(dev, 0, ALLOW_LEGACY))
+		return -ENOTSUPP;
+
 	rc = pci_setup_msi_context(dev);
 	if (rc)
 		return rc;

Alexandre Ghiti

author Tested-by

2024-12-13 13:52 UTC #2 lore raw

Hi Thomas,

Quoted 12 lines · Thomas Gleixner

Quoted 9 lines · Alexandre Ghiti

When the interrupt controller is not using the IMSIC and ACPI is enabled, the following warning appears:

[    0.866401] WARNING: CPU: 1 PID: 1 at drivers/pci/msi/msi.h:121 pci_msi_setup_msi_irqs+0x2c/0x32
[    0.867071] Modules linked in:
[    0.867389] CPU: 1 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.13.0-rc2-00001-g795582ce7e24-dirty #44
[    0.867538] Hardware name: QEMU QEMU Virtual Machine, BIOS
[    0.867672] epc : pci_msi_setup_msi_irqs+0x2c/0x32
[    0.867738]  ra : __pci_enable_msix_range+0x30c/0x596

Quoted 3 lines

Removing a ton of badly formatted stack trace:
https://www.kernel.org/doc/html/latest/process/submitting-patches.html#backtraces-in-commit-messages

Thanks for the pointer.

Quoted 10 lines

Quoted 3 lines
So enable PCI_MSI_ARCH_FALLBACKS to get rid of this.
No. PCI_MSI_ARCH_FALLBACKS is really only meant for architectures which implement the legacy fallbacks and not to paper over the underlying logic bug in the pci/msi code. Of course the loongson folks ran into the same problem two years ago and went for the sloppy fix without talking to anyone...

Quoted 4 lines

Thanks for bringing it up instead of silently slapping it into the RISCV tree !
The uncompiled patch below should fix this for real.

It does, when applied the warning disappears (on riscv at least). You can add:

Tested-by Alexandre Ghiti <[email protected]> # riscv

Thanks for your quick answer!

Alex

Quoted 44 lines

Thanks,

tglx
---

arch/loongarch/Kconfig +0 -1

@@ -185,7 +185,6 @@ config LOONGARCH
        select PCI_DOMAINS_GENERIC
        select PCI_ECAM if ACPI
        select PCI_LOONGSON
-       select PCI_MSI_ARCH_FALLBACKS
        select PCI_QUIRKS
        select PERF_USE_VMALLOC
        select RTC_LIB

drivers/pci/msi/irqdomain.c +5 -2

@@ -350,8 +350,11 @@ bool pci_msi_domain_supports(struct pci_
 
        domain = dev_get_msi_domain(&pdev->dev);
 
-       if (!domain || !irq_domain_is_hierarchy(domain))
-               return mode == ALLOW_LEGACY;
+       if (!domain || !irq_domain_is_hierarchy(domain)) {
+               if (IS_ENABLED(CONFIG_PCI_MSI_ARCH_FALLBACKS))
+                       return mode == ALLOW_LEGACY;
+               return false;
+       }
 
        if (!irq_domain_is_msi_parent(domain)) {
                /*

drivers/pci/msi/msi.c +4 -0

@@ -442,6 +442,10 @@ int __pci_enable_msi_range(struct pci_de
        if (nvec > maxvec)
                nvec = maxvec;
 
+       /* Test for the availability of MSI support */
+       if (!pci_msi_domain_supports(dev, 0, ALLOW_LEGACY))
+               return -ENOTSUPP;
+
        rc = pci_setup_msi_context(dev);
        if (rc)
                return rc;

Thomas Gleixner

2024-12-14 11:50 UTC #3 lore raw

PATCH 1/1 PCI/MSI: Handle lack of irqdomain gracefully

Alexandre observed a warning emitted from pci_msi_setup_msi_irqs() on a RISCV platform which does not provide PCI/MSI support:

 WARNING: CPU: 1 PID: 1 at drivers/pci/msi/msi.h:121 pci_msi_setup_msi_irqs+0x2c/0x32
 __pci_enable_msix_range+0x30c/0x596
 pci_msi_setup_msi_irqs+0x2c/0x32
 pci_alloc_irq_vectors_affinity+0xb8/0xe2

RISCV uses hierarchical interrupt domains and correctly does not implement the legacy fallback. The warning triggers from the legacy fallback stub.

That warning is bogus as the PCI/MSI layer knows whether a PCI/MSI parent domain is associated with the device or not. There is a check for MSI-X, which has a legacy assumption. But that legacy fallback assumption is only valid when legacy support is enabled, but otherwise the check should simply return -ENOTSUPP.

Loongarch tripped over the same problem and blindly enabled legacy support without implementing the legacy fallbacks. There are weak implementations which return an error, so the problem was papered over.

Correct pci_msi_domain_supports() to evaluate the legacy mode and add the missing supported check into the MSI enable path to complete it.

Fixes d2a463b29741 ("PCI/MSI: Reject multi-MSI early")

Reported-by Alexandre Ghiti <[email protected]>

Signed-off-by Thomas Gleixner <[email protected]>

Tested-by Alexandre Ghiti <[email protected]>

Cc [email protected]

---
 drivers/pci/msi/irqdomain.c |    7 +++++--
 drivers/pci/msi/msi.c       |    4 ++++
 2 files changed, 9 insertions(+), 2 deletions(-)

drivers/pci/msi/irqdomain.c +5 -2

@@ -350,8 +350,11 @@ bool pci_msi_domain_supports(struct pci_
 
 	domain = dev_get_msi_domain(&pdev->dev);
 
-	if (!domain || !irq_domain_is_hierarchy(domain))
-		return mode == ALLOW_LEGACY;
+	if (!domain || !irq_domain_is_hierarchy(domain)) {
+		if (IS_ENABLED(CONFIG_PCI_MSI_ARCH_FALLBACKS))
+			return mode == ALLOW_LEGACY;
+		return false;
+	}
 
 	if (!irq_domain_is_msi_parent(domain)) {
 		/*

drivers/pci/msi/msi.c +4 -0

@@ -433,6 +433,10 @@ int __pci_enable_msi_range(struct pci_de
 	if (WARN_ON_ONCE(dev->msi_enabled))
 		return -EINVAL;
 
+	/* Test for the availability of MSI support */
+	if (!pci_msi_domain_supports(dev, 0, ALLOW_LEGACY))
+		return -ENOTSUPP;
+
 	nvec = pci_msi_vec_count(dev);
 	if (nvec < 0)
 		return nvec;

tip-bot2 for Thomas Gleixner

merge bot Applied

2024-12-17 13:08 UTC #4 lore raw

[tip: irq/urgent] PCI/MSI: Handle lack of irqdomain gracefully

The following commit has been merged into the irq/urgent branch of tip:

Commit-ID:     a60b990798eb17433d0283788280422b1bd94b18
Gitweb:        https://git.kernel.org/tip/a60b990798eb17433d0283788280422b1bd94b18
Author:        Thomas Gleixner <[email protected]>
AuthorDate:    Sat, 14 Dec 2024 12:50:18 +01:00
Committer:     Thomas Gleixner <[email protected]>
CommitterDate: Mon, 16 Dec 2024 10:59:47 +01:00

PCI/MSI: Handle lack of irqdomain gracefully

Alexandre observed a warning emitted from pci_msi_setup_msi_irqs() on a RISCV platform which does not provide PCI/MSI support:

 WARNING: CPU: 1 PID: 1 at drivers/pci/msi/msi.h:121 pci_msi_setup_msi_irqs+0x2c/0x32
 __pci_enable_msix_range+0x30c/0x596
 pci_msi_setup_msi_irqs+0x2c/0x32
 pci_alloc_irq_vectors_affinity+0xb8/0xe2

RISCV uses hierarchical interrupt domains and correctly does not implement the legacy fallback. The warning triggers from the legacy fallback stub.

Correct pci_msi_domain_supports() to evaluate the legacy mode and add the missing supported check into the MSI enable path to complete it.

Fixes d2a463b29741 ("PCI/MSI: Reject multi-MSI early")

Reported-by Alexandre Ghiti <[email protected]>

Signed-off-by Thomas Gleixner <[email protected]>

Tested-by Alexandre Ghiti <[email protected]>

Cc [email protected]

Link https://lore.kernel.org/all/87ed2a8ow5.ffs@tglx open here

---
 drivers/pci/msi/irqdomain.c | 7 +++++--
 drivers/pci/msi/msi.c       | 4 ++++
 2 files changed, 9 insertions(+), 2 deletions(-)

drivers/pci/msi/irqdomain.c +5 -2

index 5691257..d7ba879 100644
@@ -350,8 +350,11 @@ bool pci_msi_domain_supports(struct pci_dev *pdev, unsigned int feature_mask,
 
 	domain = dev_get_msi_domain(&pdev->dev);
 
-	if (!domain || !irq_domain_is_hierarchy(domain))
-		return mode == ALLOW_LEGACY;
+	if (!domain || !irq_domain_is_hierarchy(domain)) {
+		if (IS_ENABLED(CONFIG_PCI_MSI_ARCH_FALLBACKS))
+			return mode == ALLOW_LEGACY;
+		return false;
+	}
 
 	if (!irq_domain_is_msi_parent(domain)) {
 		/*

drivers/pci/msi/msi.c +4 -0

index 3a45879..2f647ca 100644
@@ -433,6 +433,10 @@ int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
 	if (WARN_ON_ONCE(dev->msi_enabled))
 		return -EINVAL;
 
+	/* Test for the availability of MSI support */
+	if (!pci_msi_domain_supports(dev, 0, ALLOW_LEGACY))
+		return -ENOTSUPP;
+
 	nvec = pci_msi_vec_count(dev);
 	if (nvec < 0)
 		return nvec;

[email protected]

CI Applied

2025-02-03 19:15 UTC #5 lore raw

Re: [Patch] PCI/MSI: Handle lack of irqdomain gracefully

In reply to Thomas Gleixner

This patch was applied to riscv/linux.git (fixes) by Thomas Gleixner <[email protected]>:

Hello:

This patch was applied to riscv/linux.git (fixes)
by Thomas Gleixner <[email protected]>:

Quoted 9 lines · On Sat, 14 Dec 2024 12:50:18 +0100 you wrote:

Alexandre observed a warning emitted from pci_msi_setup_msi_irqs() on a RISCV platform which does not provide PCI/MSI support:
 WARNING: CPU: 1 PID: 1 at drivers/pci/msi/msi.h:121 pci_msi_setup_msi_irqs+0x2c/0x32
 __pci_enable_msix_range+0x30c/0x596
 pci_msi_setup_msi_irqs+0x2c/0x32
 pci_alloc_irq_vectors_affinity+0xb8/0xe2
[...]

Here is the summary with links:
- PCI/MSI: Handle lack of irqdomain gracefully

    https://git.kernel.org/riscv/c/a60b990798eb

You are awesome, thank you!

Signature · 2 lines

Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

Uwe Kleine-König

2026-03-11 11:22 UTC #6 lore raw

Re: [Patch] PCI/MSI: Handle lack of irqdomain gracefully

In reply to Thomas Gleixner

Control: forwarded -1 https://lore.kernel.org/lkml/abE_QoS5DM-ZltaV@monoceros

#regzbot introduced: a60b990798eb17433d0283788280422b1bd94b18 #regzbot from: "Aaron D. Johnson" <[email protected]> #regzbot monitor: https://bugs.debian.org/1127635

Hello,

Quoted 21 lines · Thomas Gleixner

Alexandre observed a warning emitted from pci_msi_setup_msi_irqs() on a RISCV platform which does not provide PCI/MSI support:
 WARNING: CPU: 1 PID: 1 at drivers/pci/msi/msi.h:121 pci_msi_setup_msi_irqs+0x2c/0x32
 __pci_enable_msix_range+0x30c/0x596
 pci_msi_setup_msi_irqs+0x2c/0x32
 pci_alloc_irq_vectors_affinity+0xb8/0xe2
RISCV uses hierarchical interrupt domains and correctly does not implement the legacy fallback. The warning triggers from the legacy fallback stub.
That warning is bogus as the PCI/MSI layer knows whether a PCI/MSI parent domain is associated with the device or not. There is a check for MSI-X, which has a legacy assumption. But that legacy fallback assumption is only valid when legacy support is enabled, but otherwise the check should simply return -ENOTSUPP.
Loongarch tripped over the same problem and blindly enabled legacy support without implementing the legacy fallbacks. There are weak implementations which return an error, so the problem was papered over.

Quoted 8 lines

Correct pci_msi_domain_supports() to evaluate the legacy mode and add the missing supported check into the MSI enable path to complete it.
Fixes d2a463b29741 ("PCI/MSI: Reject multi-MSI early")
Reported-by Alexandre Ghiti <[email protected]>
Signed-off-by Thomas Gleixner <[email protected]>
Tested-by Alexandre Ghiti <[email protected]>
Cc [email protected]

this patch became a60b990798eb17433d0283788280422b1bd94b18 in v6.13-rc5 and was backported to 6.12.y and 6.6.y (aed157301c65 and b1f7476e07b9 respectively).

A Debian user (Aaron, on Cc:) on powerpc has boot problems and bisected them to this commit. The relevant boot log of the failure is:

[    2.643879] BUG: Kernel NULL pointer dereference on read at 0x00000000
[    2.643891] Faulting instruction address: 0xc000000000a39514
[    2.643902] Oops: Kernel access of bad area, sig: 11 [#1]
[    2.643909] BE PAGE_SIZE=4K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
[    2.643920] Modules linked in: ohci_pci(+) ehci_hcd nvme_fabrics ohci_hcd nvme_keyring nvme_core usbcore nvme_auth scsi_transport_fc ipr configfs ehea(+) usb_common
[    2.643965] CPU: 5 UID: 0 PID: 250 Comm: (udev-worker) Not tainted 6.12.17-powerpc64 #1  Debian 6.12.17-1
[    2.643976] Hardware name: IBM,8204-E8A POWER6 (architected) 0x3e0302 0xf000002 of:IBM,EL350_118 hv:phyp pSeries
[    2.643986] NIP:  c000000000a39514 LR: c000000000a36ed8 CTR: c000000000a35820
[    2.643995] REGS: c0000000351f6f60 TRAP: 0300   Not tainted  (6.12.17-powerpc64 Debian 6.12.17-1)
[    2.644004] MSR:  8000000000009032 <SF,EE,ME,IR,DR,RI>  CR: 24222288  XER: 00000000
[    2.644031] CFAR: c00000000000cfc4 DAR: 0000000000000000 DSISR: 40000000 IRQMASK: 0
[    2.644031] GPR00: c000000000a36ed8 c0000000351f7200 c00000000182e200 c0000003df294000
[    2.644031] GPR04: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[    2.644031] GPR08: 0000000000000001 0000000000000000 c00000000228fcc0 0000000044222288
[    2.644031] GPR12: c000000000a35820 c00000000eeacb00 0000000000000020 0000010037fcab20
[    2.644031] GPR16: 0000000022222248 0000000000020000 0000000000000000 00003fffebe8bb80
[    2.644031] GPR20: 0000000000000000 c00000000204db60 c00000000204dd60 c00000000b1ae780
[    2.644031] GPR24: 0000000000000000 00003fff8c9ac758 0000000000000000 c0000003df294000
[    2.644031] GPR28: 0000000000000001 0000000000000000 c0000003df294000 0000000000000001
[    2.644164] NIP [c000000000a39514] pci_msi_domain_supports (drivers/pci/msi/irqdomain.c:366)
[    2.644181] LR [c000000000a36ed8] __pci_enable_msi_range (drivers/pci/msi/msi.c:437)
[    2.644192] Call Trace:
[    2.644197] [c0000000351f7200] [c0000000351f7304] 0xc0000000351f7304 (unreliable)
[    2.644211] [c0000000351f7340] [c000000000a3578c] pci_alloc_irq_vectors_affinity (drivers/pci/msi/api.c:277)
[    2.644225] [c0000000351f73d0] [c0003d0007d2f4d4] usb_hcd_pci_probe (drivers/usb/core/hcd-pci.c:192) usbcore
[    2.644246] [c0000000351f7470] [c0003d00084e6030] ohci_pci_probe (drivers/usb/host/ohci-pci.c:285) ohci_pci
[    2.644260] [c0000000351f7490] [c000000000a260e8] local_pci_probe (drivers/pci/pci-driver.c:324)
[    2.644274] [c0000000351f7510] [c000000000a26218] pci_call_probe (drivers/pci/pci-driver.c:392 (discriminator 1))
[    2.644287] [c0000000351f7670] [c000000000a27348] pci_device_probe (drivers/pci/pci-driver.c:452)
[    2.644300] [c0000000351f76b0] [c000000000b2e658] really_probe (drivers/base/dd.c:579 drivers/base/dd.c:658)
[    2.644314] [c0000000351f7740] [c000000000b2eb24] __driver_probe_device (drivers/base/dd.c:800)
[    2.644327] [c0000000351f77c0] [c000000000b2edc4] driver_probe_device (drivers/base/dd.c:831)
[    2.644340] [c0000000351f7800] [c000000000b2f188] __driver_attach (drivers/base/dd.c:1217)
[    2.644352] [c0000000351f7880] [c000000000b2ac64] bus_for_each_dev (drivers/base/bus.c:370)
[    2.644365] [c0000000351f78e0] [c000000000b2dac4] driver_attach (drivers/base/dd.c:1234)
[    2.644377] [c0000000351f7900] [c000000000b2cd98] bus_add_driver (drivers/base/bus.c:675)
[    2.644389] [c0000000351f7990] [c000000000b30ae4] driver_register (drivers/base/driver.c:246)
[    2.644402] [c0000000351f7a00] [c000000000a24f88] __pci_register_driver (drivers/pci/pci-driver.c:1450)
[    2.644415] [c0000000351f7a20] [c0003d00084e6800] ohci_pci_init (drivers/usb/host/ohci-pci.c:308) ohci_pci
[    2.644429] [c0000000351f7a50] [c00000000000fd60] do_one_initcall (init/main.c:1269)
[    2.644444] [c0000000351f7b30] [c0000000002760f8] do_init_module (kernel/module/main.c:2543)
[    2.644460] [c0000000351f7bb0] [c000000000278fe4] init_module_from_file (kernel/module/main.c:3199)
[    2.644473] [c0000000351f7c90] [c0000000002793e0] sys_finit_module (kernel/module/main.c:3211 kernel/module/main.c:3238 kernel/module/main.c:3221)
[    2.644487] [c0000000351f7da0] [c00000000002c084] system_call_exception (arch/powerpc/kernel/syscall.c:171)
[    2.644500] [c0000000351f7e50] [c00000000000cb54] system_call_common (arch/powerpc/kernel/interrupt_64.S:292)
[    2.644515] --- interrupt: c00 at 0x3fff8d653d8c
[    2.644522] NIP:  00003fff8d653d8c LR: 00003fff8c9a4680 CTR: 0000000000000000
[    2.644531] REGS: c0000000351f7e80 TRAP: 0c00   Not tainted  (6.12.17-powerpc64 Debian 6.12.17-1)
[    2.644541] MSR:  800000000200f032 <SF,VEC,EE,PR,FP,ME,IR,DR,RI>  CR: 22222222  XER: 00000000
[    2.644573] IRQMASK: 0
[    2.644573] GPR00: 0000000000000161 00003fffebe8b640 00003fff8d757100 0000000000000052
[    2.644573] GPR04: 00003fff8c9ac758 0000000000000004 0000000000000058 000000000000005a
[    2.644573] GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[    2.644573] GPR12: 0000000000000000 00003fff8de947c0 0000000000000020 0000010037fcab20
[    2.644573] GPR16: 0000000022222248 0000000000020000 0000000000000000 00003fffebe8bb80
[    2.644573] GPR20: 0000000000000000 00003fffebe8bb70 0000000000000007 0000010037fca210
[    2.644573] GPR24: 0000000000000000 0000000000000000 0000010037f6be40 0000000000000004
[    2.644573] GPR28: 00003fff8c9ac758 0000000000020000 0000000000000004 0000010037fca210
[    2.644698] NIP [00003fff8d653d8c] 0x3fff8d653d8c
[    2.644705] LR [00003fff8c9a4680] 0x3fff8c9a4680
[    2.644713] --- interrupt: c00
[ 2.644719] Code: 4182002c e92a0088 80690000 7c632038 7c632278 7c630034 5463d97e 786307e0 4e800020 60000000 60000000 e92a0020 <80690000> 4bffffd8 60000000 7ca50034
All code
========
   0:*	41 82 00 2c 	beq     0x2c		<-- trapping instruction
   4:	e9 2a 00 88 	ld      r9,136(r10)
   8:	80 69 00 00 	lwz     r3,0(r9)
   c:	7c 63 20 38 	and     r3,r3,r4
  10:	7c 63 22 78 	xor     r3,r3,r4
  14:	7c 63 00 34 	cntlzw  r3,r3
  18:	54 63 d9 7e 	srwi    r3,r3,5
  1c:	78 63 07 e0 	clrldi  r3,r3,63
  20:	4e 80 00 20 	blr
  24:	60 00 00 00 	nop
  28:	60 00 00 00 	nop
  2c:	e9 2a 00 20 	ld      r9,32(r10)
  30:	80 69 00 00 	lwz     r3,0(r9)
  34:	4b ff ff d8 	b       0xc

38: 60 00 00 00 nop
3c: 7c a5 00 34 cntlzw r5,r5

Code starting with the faulting instruction
===========================================
0: 80 69 00 00 lwz r3,0(r9)
4: 4b ff ff d8 b 0xffffffffffffffdc
8: 60 00 00 00 nop
c: 7c a5 00 34 cntlzw r5,r5

[    2.644769] ---[ end trace 0000000000000000 ]---

(That's the bug splat from the bug report piped through scripts/decode_stacktrace.sh)

The kernel has CONFIG_PCI_MSI_ARCH_FALLBACKS=y, so the first hunk shouldn't change anything.

The disassembly of pci_msi_domain_supports in the kernel looks as follows:

	c000000000a394c0 <pci_msi_domain_supports>:
	pci_msi_domain_supports():
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:334
	c000000000a394c0:       60 00 00 00     nop
	c000000000a394c4:       60 00 00 00     nop
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:353
	c000000000a394c8:       e9 43 02 e8     ld      r10,744(r3)
	c000000000a394cc:       2c 2a 00 00     cmpdi   r10,0
	c000000000a394d0:       41 82 00 50     beq     c000000000a39520 <pci_msi_domain_supports+0x60>
	irq_domain_is_hierarchy():
	debian/build/build_powerpc_none_powerpc64/include/linux/irqdomain.h:661
	c000000000a394d4:       81 2a 00 28     lwz     r9,40(r10)
	pci_msi_domain_supports():
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:353 (discriminator 1)
	c000000000a394d8:       71 28 00 01     andi.   r8,r9,1
	c000000000a394dc:       41 82 00 44     beq     c000000000a39520 <pci_msi_domain_supports+0x60>
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:359 (discriminator 1)
	c000000000a394e0:       71 29 01 00     andi.   r9,r9,256
	c000000000a394e4:       41 82 00 2c     beq     c000000000a39510 <pci_msi_domain_supports+0x50>
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:375
	c000000000a394e8:       e9 2a 00 88     ld      r9,136(r10)
	c000000000a394ec:       80 69 00 00     lwz     r3,0(r9)
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:378
	c000000000a394f0:       7c 63 20 38     and     r3,r3,r4
	c000000000a394f4:       7c 63 22 78     xor     r3,r3,r4
	c000000000a394f8:       7c 63 00 34     cntlzw  r3,r3
	c000000000a394fc:       54 63 d9 7e     srwi    r3,r3,5
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:379
	c000000000a39500:       78 63 07 e0     clrldi  r3,r3,63
	c000000000a39504:       4e 80 00 20     blr
	c000000000a39508:       60 00 00 00     nop
	c000000000a3950c:       60 00 00 00     nop
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:366
	c000000000a39510:       e9 2a 00 20     ld      r9,32(r10)
	c000000000a39514:       80 69 00 00     lwz     r3,0(r9)
	c000000000a39518:       4b ff ff d8     b       c000000000a394f0 <pci_msi_domain_supports+0x30>
	c000000000a3951c:       60 00 00 00     nop
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:355
	c000000000a39520:       7c a5 00 34     cntlzw  r5,r5
	c000000000a39524:       54 a3 d9 7e     srwi    r3,r5,5
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:379
	c000000000a39528:       78 63 07 e0     clrldi  r3,r3,63
	c000000000a3952c:       4e 80 00 20     blr

so the trapping happens in drivers/pci/msi/irqdomain.c:366 which is:

365 info = domain->host_data;
366 supported = info->flags;

According to the register dump domain == r10 == NULL, but then this code would not have been reached and the faulting instruction would be at c000000000a39510. So maybe it's only .host_data = NULL and the register dump is unreliable??

The offsets match: .host_data is at offset 32 of struct irq_domain and .flags is at offset 0 of struct msi_domain_info.

For more details see
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1127635 .

Does someone spot the issue?

Best regards
Uwe

Thorsten Leemhuis

2026-04-22 08:50 UTC #7 lore raw

Re: [Patch] PCI/MSI: Handle lack of irqdomain gracefully

Quoted 3 lines · Uwe Kleine-König

Control: forwarded -1 https://lore.kernel.org/lkml/abE_QoS5DM-ZltaV@monoceros
#regzbot introduced: a60b990798eb17433d0283788280422b1bd94b18

Thomas, in case you missed it: this is a change of yours: a60b990798eb17 ("PCI/MSI: Handle lack of irqdomain gracefully") [v6.13-rc5]

Quoted 2 lines

#regzbot from: "Aaron D. Johnson" <[email protected]> #regzbot monitor: https://bugs.debian.org/1127635

Thx for forwarding the regression. Nothing happened since then -- or am I missing something? If so: is that okay for everybody, or should we do anything about this?

BTW, did anyone check if this happens with mainline (6.13/7.0) as well to rule out that this is something that only happenens in the stable series it was backported too? If it's the latter I wonder if reverting it there might be a easy way to resolve this.

Ciao, Thorsten

Quoted 202 lines · Alexander Stein

Quoted 21 lines · Thomas Gleixner

Alexandre observed a warning emitted from pci_msi_setup_msi_irqs() on a RISCV platform which does not provide PCI/MSI support:
 WARNING: CPU: 1 PID: 1 at drivers/pci/msi/msi.h:121 pci_msi_setup_msi_irqs+0x2c/0x32
 __pci_enable_msix_range+0x30c/0x596
 pci_msi_setup_msi_irqs+0x2c/0x32
 pci_alloc_irq_vectors_affinity+0xb8/0xe2
RISCV uses hierarchical interrupt domains and correctly does not implement the legacy fallback. The warning triggers from the legacy fallback stub.
That warning is bogus as the PCI/MSI layer knows whether a PCI/MSI parent domain is associated with the device or not. There is a check for MSI-X, which has a legacy assumption. But that legacy fallback assumption is only valid when legacy support is enabled, but otherwise the check should simply return -ENOTSUPP.
Loongarch tripped over the same problem and blindly enabled legacy support without implementing the legacy fallbacks. There are weak implementations which return an error, so the problem was papered over.

Quoted 8 lines

Correct pci_msi_domain_supports() to evaluate the legacy mode and add the missing supported check into the MSI enable path to complete it.
Fixes d2a463b29741 ("PCI/MSI: Reject multi-MSI early")
Reported-by Alexandre Ghiti <[email protected]>
Signed-off-by Thomas Gleixner <[email protected]>
Tested-by Alexandre Ghiti <[email protected]>
Cc [email protected]

this patch became a60b990798eb17433d0283788280422b1bd94b18 in v6.13-rc5 and was backported to 6.12.y and 6.6.y (aed157301c65 and b1f7476e07b9 respectively).

A Debian user (Aaron, on Cc:) on powerpc has boot problems and bisected them to this commit. The relevant boot log of the failure is:

[    2.643879] BUG: Kernel NULL pointer dereference on read at 0x00000000
[    2.643891] Faulting instruction address: 0xc000000000a39514
[    2.643902] Oops: Kernel access of bad area, sig: 11 [#1]
[    2.643909] BE PAGE_SIZE=4K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
[    2.643920] Modules linked in: ohci_pci(+) ehci_hcd nvme_fabrics ohci_hcd nvme_keyring nvme_core usbcore nvme_auth scsi_transport_fc ipr configfs ehea(+) usb_common
[    2.643965] CPU: 5 UID: 0 PID: 250 Comm: (udev-worker) Not tainted 6.12.17-powerpc64 #1  Debian 6.12.17-1
[    2.643976] Hardware name: IBM,8204-E8A POWER6 (architected) 0x3e0302 0xf000002 of:IBM,EL350_118 hv:phyp pSeries
[    2.643986] NIP:  c000000000a39514 LR: c000000000a36ed8 CTR: c000000000a35820
[    2.643995] REGS: c0000000351f6f60 TRAP: 0300   Not tainted  (6.12.17-powerpc64 Debian 6.12.17-1)
[    2.644004] MSR:  8000000000009032 <SF,EE,ME,IR,DR,RI>  CR: 24222288  XER: 00000000
[    2.644031] CFAR: c00000000000cfc4 DAR: 0000000000000000 DSISR: 40000000 IRQMASK: 0
[    2.644031] GPR00: c000000000a36ed8 c0000000351f7200 c00000000182e200 c0000003df294000
[    2.644031] GPR04: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[    2.644031] GPR08: 0000000000000001 0000000000000000 c00000000228fcc0 0000000044222288
[    2.644031] GPR12: c000000000a35820 c00000000eeacb00 0000000000000020 0000010037fcab20
[    2.644031] GPR16: 0000000022222248 0000000000020000 0000000000000000 00003fffebe8bb80
[    2.644031] GPR20: 0000000000000000 c00000000204db60 c00000000204dd60 c00000000b1ae780
[    2.644031] GPR24: 0000000000000000 00003fff8c9ac758 0000000000000000 c0000003df294000
[    2.644031] GPR28: 0000000000000001 0000000000000000 c0000003df294000 0000000000000001
[    2.644164] NIP [c000000000a39514] pci_msi_domain_supports (drivers/pci/msi/irqdomain.c:366)
[    2.644181] LR [c000000000a36ed8] __pci_enable_msi_range (drivers/pci/msi/msi.c:437)
[    2.644192] Call Trace:
[    2.644197] [c0000000351f7200] [c0000000351f7304] 0xc0000000351f7304 (unreliable)
[    2.644211] [c0000000351f7340] [c000000000a3578c] pci_alloc_irq_vectors_affinity (drivers/pci/msi/api.c:277)
[    2.644225] [c0000000351f73d0] [c0003d0007d2f4d4] usb_hcd_pci_probe (drivers/usb/core/hcd-pci.c:192) usbcore
[    2.644246] [c0000000351f7470] [c0003d00084e6030] ohci_pci_probe (drivers/usb/host/ohci-pci.c:285) ohci_pci
[    2.644260] [c0000000351f7490] [c000000000a260e8] local_pci_probe (drivers/pci/pci-driver.c:324)
[    2.644274] [c0000000351f7510] [c000000000a26218] pci_call_probe (drivers/pci/pci-driver.c:392 (discriminator 1))
[    2.644287] [c0000000351f7670] [c000000000a27348] pci_device_probe (drivers/pci/pci-driver.c:452)
[    2.644300] [c0000000351f76b0] [c000000000b2e658] really_probe (drivers/base/dd.c:579 drivers/base/dd.c:658)
[    2.644314] [c0000000351f7740] [c000000000b2eb24] __driver_probe_device (drivers/base/dd.c:800)
[    2.644327] [c0000000351f77c0] [c000000000b2edc4] driver_probe_device (drivers/base/dd.c:831)
[    2.644340] [c0000000351f7800] [c000000000b2f188] __driver_attach (drivers/base/dd.c:1217)
[    2.644352] [c0000000351f7880] [c000000000b2ac64] bus_for_each_dev (drivers/base/bus.c:370)
[    2.644365] [c0000000351f78e0] [c000000000b2dac4] driver_attach (drivers/base/dd.c:1234)
[    2.644377] [c0000000351f7900] [c000000000b2cd98] bus_add_driver (drivers/base/bus.c:675)
[    2.644389] [c0000000351f7990] [c000000000b30ae4] driver_register (drivers/base/driver.c:246)
[    2.644402] [c0000000351f7a00] [c000000000a24f88] __pci_register_driver (drivers/pci/pci-driver.c:1450)
[    2.644415] [c0000000351f7a20] [c0003d00084e6800] ohci_pci_init (drivers/usb/host/ohci-pci.c:308) ohci_pci
[    2.644429] [c0000000351f7a50] [c00000000000fd60] do_one_initcall (init/main.c:1269)
[    2.644444] [c0000000351f7b30] [c0000000002760f8] do_init_module (kernel/module/main.c:2543)
[    2.644460] [c0000000351f7bb0] [c000000000278fe4] init_module_from_file (kernel/module/main.c:3199)
[    2.644473] [c0000000351f7c90] [c0000000002793e0] sys_finit_module (kernel/module/main.c:3211 kernel/module/main.c:3238 kernel/module/main.c:3221)
[    2.644487] [c0000000351f7da0] [c00000000002c084] system_call_exception (arch/powerpc/kernel/syscall.c:171)
[    2.644500] [c0000000351f7e50] [c00000000000cb54] system_call_common (arch/powerpc/kernel/interrupt_64.S:292)
[    2.644515] --- interrupt: c00 at 0x3fff8d653d8c
[    2.644522] NIP:  00003fff8d653d8c LR: 00003fff8c9a4680 CTR: 0000000000000000
[    2.644531] REGS: c0000000351f7e80 TRAP: 0c00   Not tainted  (6.12.17-powerpc64 Debian 6.12.17-1)
[    2.644541] MSR:  800000000200f032 <SF,VEC,EE,PR,FP,ME,IR,DR,RI>  CR: 22222222  XER: 00000000
[    2.644573] IRQMASK: 0
[    2.644573] GPR00: 0000000000000161 00003fffebe8b640 00003fff8d757100 0000000000000052
[    2.644573] GPR04: 00003fff8c9ac758 0000000000000004 0000000000000058 000000000000005a
[    2.644573] GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[    2.644573] GPR12: 0000000000000000 00003fff8de947c0 0000000000000020 0000010037fcab20
[    2.644573] GPR16: 0000000022222248 0000000000020000 0000000000000000 00003fffebe8bb80
[    2.644573] GPR20: 0000000000000000 00003fffebe8bb70 0000000000000007 0000010037fca210
[    2.644573] GPR24: 0000000000000000 0000000000000000 0000010037f6be40 0000000000000004
[    2.644573] GPR28: 00003fff8c9ac758 0000000000020000 0000000000000004 0000010037fca210
[    2.644698] NIP [00003fff8d653d8c] 0x3fff8d653d8c
[    2.644705] LR [00003fff8c9a4680] 0x3fff8c9a4680
[    2.644713] --- interrupt: c00
[ 2.644719] Code: 4182002c e92a0088 80690000 7c632038 7c632278 7c630034 5463d97e 786307e0 4e800020 60000000 60000000 e92a0020 <80690000> 4bffffd8 60000000 7ca50034
All code
========
   0:*	41 82 00 2c 	beq     0x2c		<-- trapping instruction
   4:	e9 2a 00 88 	ld      r9,136(r10)
   8:	80 69 00 00 	lwz     r3,0(r9)
   c:	7c 63 20 38 	and     r3,r3,r4
  10:	7c 63 22 78 	xor     r3,r3,r4
  14:	7c 63 00 34 	cntlzw  r3,r3
  18:	54 63 d9 7e 	srwi    r3,r3,5
  1c:	78 63 07 e0 	clrldi  r3,r3,63
  20:	4e 80 00 20 	blr
  24:	60 00 00 00 	nop
  28:	60 00 00 00 	nop
  2c:	e9 2a 00 20 	ld      r9,32(r10)
  30:	80 69 00 00 	lwz     r3,0(r9)
  34:	4b ff ff d8 	b       0xc

38: 60 00 00 00 nop
3c: 7c a5 00 34 cntlzw r5,r5

[    2.644769] ---[ end trace 0000000000000000 ]---

(That's the bug splat from the bug report piped through scripts/decode_stacktrace.sh)

The kernel has CONFIG_PCI_MSI_ARCH_FALLBACKS=y, so the first hunk shouldn't change anything.

The disassembly of pci_msi_domain_supports in the kernel looks as follows:

	c000000000a394c0 <pci_msi_domain_supports>:
	pci_msi_domain_supports():
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:334
	c000000000a394c0:       60 00 00 00     nop
	c000000000a394c4:       60 00 00 00     nop
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:353
	c000000000a394c8:       e9 43 02 e8     ld      r10,744(r3)
	c000000000a394cc:       2c 2a 00 00     cmpdi   r10,0
	c000000000a394d0:       41 82 00 50     beq     c000000000a39520 <pci_msi_domain_supports+0x60>
	irq_domain_is_hierarchy():
	debian/build/build_powerpc_none_powerpc64/include/linux/irqdomain.h:661
	c000000000a394d4:       81 2a 00 28     lwz     r9,40(r10)
	pci_msi_domain_supports():
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:353 (discriminator 1)
	c000000000a394d8:       71 28 00 01     andi.   r8,r9,1
	c000000000a394dc:       41 82 00 44     beq     c000000000a39520 <pci_msi_domain_supports+0x60>
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:359 (discriminator 1)
	c000000000a394e0:       71 29 01 00     andi.   r9,r9,256
	c000000000a394e4:       41 82 00 2c     beq     c000000000a39510 <pci_msi_domain_supports+0x50>
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:375
	c000000000a394e8:       e9 2a 00 88     ld      r9,136(r10)
	c000000000a394ec:       80 69 00 00     lwz     r3,0(r9)
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:378
	c000000000a394f0:       7c 63 20 38     and     r3,r3,r4
	c000000000a394f4:       7c 63 22 78     xor     r3,r3,r4
	c000000000a394f8:       7c 63 00 34     cntlzw  r3,r3
	c000000000a394fc:       54 63 d9 7e     srwi    r3,r3,5
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:379
	c000000000a39500:       78 63 07 e0     clrldi  r3,r3,63
	c000000000a39504:       4e 80 00 20     blr
	c000000000a39508:       60 00 00 00     nop
	c000000000a3950c:       60 00 00 00     nop
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:366
	c000000000a39510:       e9 2a 00 20     ld      r9,32(r10)
	c000000000a39514:       80 69 00 00     lwz     r3,0(r9)
	c000000000a39518:       4b ff ff d8     b       c000000000a394f0 <pci_msi_domain_supports+0x30>
	c000000000a3951c:       60 00 00 00     nop
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:355
	c000000000a39520:       7c a5 00 34     cntlzw  r5,r5
	c000000000a39524:       54 a3 d9 7e     srwi    r3,r5,5
	debian/build/build_powerpc_none_powerpc64/drivers/pci/msi/irqdomain.c:379
	c000000000a39528:       78 63 07 e0     clrldi  r3,r3,63
	c000000000a3952c:       4e 80 00 20     blr

so the trapping happens in drivers/pci/msi/irqdomain.c:366 which is:

365 info = domain->host_data;
366 supported = info->flags;

The offsets match: .host_data is at offset 32 of struct irq_domain and .flags is at offset 0 of struct msi_domain_info.

For more details see
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1127635 .

Does someone spot the issue?

Best regards
Uwe

Aaron D. Johnson

2026-04-22 15:16 UTC #8 lore raw

Re: [Patch] PCI/MSI: Handle lack of irqdomain gracefully

Quoted 3 lines · Thorsten Leemhuis

Thx for forwarding the regression. Nothing happened since then -- or am I missing something? If so: is that okay for everybody, or should we do anything about this?

I have not seen any discussion. As the initial reporter, I can accept that it is a very niche hardware platform and may well go unfixed forever. The machine in question has left my possession. It may come back in the future. Or maybe not. The next-generation newer ppc64 machine I have (an IBM 8205-E6C p740) does not exhibit this behavior.

Quoted 4 lines

BTW, did anyone check if this happens with mainline (6.13/7.0) as well to rule out that this is something that only happenens in the stable series it was backported too? If it's the latter I wonder if reverting it there might be a easy way to resolve this.

I didn't check mainline specifically, no. All bisection was done against the stable git repo.

Thanks!

- Aaron

Thomas Gleixner

2026-04-22 19:52 UTC #9 lore raw

Re: [Patch] PCI/MSI: Handle lack of irqdomain gracefully

In reply to Thorsten Leemhuis

Quoted 7 lines · Thorsten Leemhuis

Quoted 3 lines · Uwe Kleine-König
Control: forwarded -1 https://lore.kernel.org/lkml/abE_QoS5DM-ZltaV@monoceros
#regzbot introduced: a60b990798eb17433d0283788280422b1bd94b18
Thomas, in case you missed it: this is a change of yours: a60b990798eb17 ("PCI/MSI: Handle lack of irqdomain gracefully") [v6.13-rc5]

Yes. That fell through the cracks.

Quoted 11 lines

Quoted 2 lines
#regzbot from: "Aaron D. Johnson" <[email protected]> #regzbot monitor: https://bugs.debian.org/1127635
Thx for forwarding the regression. Nothing happened since then -- or am I missing something? If so: is that okay for everybody, or should we do anything about this?
BTW, did anyone check if this happens with mainline (6.13/7.0) as well to rule out that this is something that only happenens in the stable series it was backported too? If it's the latter I wonder if reverting it there might be a easy way to resolve this.

Let me have a look.

Thomas Gleixner

2026-04-22 21:22 UTC #10 lore raw

Re: [Patch] PCI/MSI: Handle lack of irqdomain gracefully

In reply to Uwe Kleine-König

Quoted 47 lines · Uwe Kleine-König

this patch became a60b990798eb17433d0283788280422b1bd94b18 in v6.13-rc5 and was backported to 6.12.y and 6.6.y (aed157301c65 and b1f7476e07b9 respectively).

A Debian user (Aaron, on Cc:) on powerpc has boot problems and bisected them to this commit. The relevant boot log of the failure is:

[    2.643879] BUG: Kernel NULL pointer dereference on read at 0x00000000
[    2.643891] Faulting instruction address: 0xc000000000a39514
[    2.643902] Oops: Kernel access of bad area, sig: 11 [#1]
[    2.643909] BE PAGE_SIZE=4K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
[    2.643920] Modules linked in: ohci_pci(+) ehci_hcd nvme_fabrics ohci_hcd nvme_keyring nvme_core usbcore nvme_auth scsi_transport_fc ipr configfs ehea(+) usb_common
[    2.643965] CPU: 5 UID: 0 PID: 250 Comm: (udev-worker) Not tainted 6.12.17-powerpc64 #1  Debian 6.12.17-1
[    2.643976] Hardware name: IBM,8204-E8A POWER6 (architected) 0x3e0302 0xf000002 of:IBM,EL350_118 hv:phyp pSeries
[    2.643986] NIP:  c000000000a39514 LR: c000000000a36ed8 CTR: c000000000a35820
[    2.643995] REGS: c0000000351f6f60 TRAP: 0300   Not tainted  (6.12.17-powerpc64 Debian 6.12.17-1)
[    2.644004] MSR:  8000000000009032 <SF,EE,ME,IR,DR,RI>  CR: 24222288  XER: 00000000
[    2.644031] CFAR: c00000000000cfc4 DAR: 0000000000000000 DSISR: 40000000 IRQMASK: 0
[    2.644031] GPR00: c000000000a36ed8 c0000000351f7200 c00000000182e200 c0000003df294000
[    2.644031] GPR04: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[    2.644031] GPR08: 0000000000000001 0000000000000000 c00000000228fcc0 0000000044222288
[    2.644031] GPR12: c000000000a35820 c00000000eeacb00 0000000000000020 0000010037fcab20
[    2.644031] GPR16: 0000000022222248 0000000000020000 0000000000000000 00003fffebe8bb80
[    2.644031] GPR20: 0000000000000000 c00000000204db60 c00000000204dd60 c00000000b1ae780
[    2.644031] GPR24: 0000000000000000 00003fff8c9ac758 0000000000000000 c0000003df294000
[    2.644031] GPR28: 0000000000000001 0000000000000000 c0000003df294000 0000000000000001
[    2.644164] NIP [c000000000a39514] pci_msi_domain_supports (drivers/pci/msi/irqdomain.c:366)
[    2.644181] LR [c000000000a36ed8] __pci_enable_msi_range (drivers/pci/msi/msi.c:437)
[    2.644192] Call Trace:
[    2.644197] [c0000000351f7200] [c0000000351f7304] 0xc0000000351f7304 (unreliable)
[    2.644211] [c0000000351f7340] [c000000000a3578c] pci_alloc_irq_vectors_affinity (drivers/pci/msi/api.c:277)

========
0:* 41 82 00 2c beq 0x2c <-- trapping instruction

   4:	e9 2a 00 88 	ld      r9,136(r10)
   8:	80 69 00 00 	lwz     r3,0(r9)
   c:	7c 63 20 38 	and     r3,r3,r4
  10:	7c 63 22 78 	xor     r3,r3,r4
  14:	7c 63 00 34 	cntlzw  r3,r3
  18:	54 63 d9 7e 	srwi    r3,r3,5
  1c:	78 63 07 e0 	clrldi  r3,r3,63
  20:	4e 80 00 20 	blr
  24:	60 00 00 00 	nop
  28:	60 00 00 00 	nop
  2c:	e9 2a 00 20 	ld      r9,32(r10)
  30:	80 69 00 00 	lwz     r3,0(r9)
  34:	4b ff ff d8 	b       0xc

Quoted 8 lines

38: 60 00 00 00 nop
3c: 7c a5 00 34 cntlzw r5,r5
Code starting with the faulting instruction
===========================================
0: 80 69 00 00 lwz r3,0(r9)
[    2.644031] GPR08: 0000000000000001 0000000000000000 c00000000228fcc0 0000000044222288

So R9 is NULL, R10 is the domain pointer.

Quoted 11 lines

   4:	4b ff ff d8 	b       0xffffffffffffffdc
   8:	60 00 00 00 	nop
   c:	7c a5 00 34 	cntlzw  r5,r5
[    2.644769] ---[ end trace 0000000000000000 ]---
(That's the bug splat from the bug report piped through scripts/decode_stacktrace.sh)
The kernel has CONFIG_PCI_MSI_ARCH_FALLBACKS=y, so the first hunk shouldn't change anything.

Correct. But the Ooops is in the unchanged code part of pci_msi_domain_supports().

Quoted 6 lines

so the trapping happens in drivers/pci/msi/irqdomain.c:366 which is:
365 info = domain->host_data;
366 supported = info->flags;
According to the register dump domain == r10 == NULL, but then this code

No. You are looking at the wrong register set. The second one is the user space register set from the syscall entry.

R10 contains the domain pointer and R9 is NULL, which does not make any sense.

On 6.12 power64 still uses the global PCI/MSI domain model. According to the splat this is pseries so the global PCI/MSI domain is created in __pseries_msi_allocate_domains() via pci_msi_create_irq_domain(). The latter takes a pointer to

       static struct msi_domain_info_pseries_msi_domain_info;

which is assigned to the global PCI/MSI domain::host_data.

Upstream got rid of that and uses per device domains, so it might have been magically fixed by now, but I doubt it:

That new check in __pci_enable_msi_range() is benign as the actual allocation code further down relies on domain::host_data being a valid pointer as well.

It might not reach that point due to the subsequent checks, but if the PCI device has pdev::dev::msi::domain populated, then this has to be either a global PCI/MSI domain or a MSI parent domain. Both have domain::host_data populated with a msi_domain_info pointer.

Something is mighty fishy here.

Aaron, can you please apply the patch below and see whether it fixes the issue and provide the dmesg with the output of those pr_warn()'s?

The other information which would be useful: When you boot a kernel with the commit reverted and look at that OHCI controller with lspci -vvv then you should see whether it has MSI enabled or not. If it has MSI enabled, then please provide the output of

/sys/kernel/debug/irq/irqs/$IRQNR

You need to enable CONFIG_GENERIC_IRQ_DEBUGFS for that.

And that's actually useful for the debug patch below too because you can then look at the domain name output and gather more information from

/sys/kernel/debug/irq/domains/$NAME

Thanks,

tglx

---
 drivers/pci/msi/irqdomain.c |   15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

drivers/pci/msi/irqdomain.c +14 -1

@@ -115,6 +115,8 @@ struct irq_domain *pci_msi_create_irq_do
 					     struct msi_domain_info *info,
 					     struct irq_domain *parent)
 {
+	struct irq_domain *domain;
+
 	if (WARN_ON(info->flags & MSI_FLAG_LEVEL_CAPABLE))
 		info->flags &= ~MSI_FLAG_LEVEL_CAPABLE;

@@ -135,7 +137,12 @@ struct irq_domain *pci_msi_create_irq_do
 	/* Let the core update the bus token */
 	info->bus_token = DOMAIN_BUS_PCI_MSI;
 
-	return msi_create_irq_domain(fwnode, info, parent);
+	domain = msi_create_irq_domain(fwnode, info, parent);
+	if (domain) {
+		pr_warn("Created global PCI/MSI domain %lx %s flags: %x\n",
+			(unsigned long)domain, domain->name, domain->flags);
+	}
+	return domain;
 }
 EXPORT_SYMBOL_GPL(pci_msi_create_irq_domain);

@@ -356,6 +363,12 @@ bool pci_msi_domain_supports(struct pci_
 		return false;
 	}
 
+	if (!domain->host_data) {
+		pr_warn("Device MSI domain %lx %s %x lacks host data\n",
+			(unsigned long)domain, domain->name, domain->flags);
+		return false;
+	}
+
 	if (!irq_domain_is_msi_parent(domain)) {
 		/*
 		 * For "global" PCI/MSI interrupt domains the associated

Aaron D. Johnson

2026-04-22 22:35 UTC #11 lore raw

Re: [Patch] PCI/MSI: Handle lack of irqdomain gracefully

Quoted 3 lines · Thomas Gleixner

Aaron, can you please apply the patch below and see whether it fixes the issue and provide the dmesg with the output of those pr_warn()'s?

I can build it. But as stated earlier, the machine is no longer in my possession. If it comes back, (and it might -- its new owner is having problems supplying sufficient input power in his apartment), I will be happy to test patches.

Quoted 8 lines

The other information which would be useful: When you boot a kernel with the commit reverted and look at that OHCI controller with lspci -vvv then you should see whether it has MSI enabled or not. If it has MSI enabled, then please provide the output of
/sys/kernel/debug/irq/irqs/$IRQNR
You need to enable CONFIG_GENERIC_IRQ_DEBUGFS for that.

Noted. And thanks for the time looking into it.

- Aaron