Linux drivers find their MSI and MSI-X registers through pdev->msi_cap and
pdev->msix_cap, which hold where those capabilities start in PCI config
space. LinuxKPI never set them, so they stayed 0, and every access meant
for the MSI registers went to the start of config space instead.

Drivers using these fields, e.g. ath11k and amdgpu, are affected.

Fill in both fields from the capability offsets that the native PCI code
already records.

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quentin.thebault_defenso.fr created this revision.Mon, Nov 2, 3:19 AM

Herald added subscribers: linuxkpi, emaste, imp. · View Herald TranscriptMon, Nov 2, 3:19 AM

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Harbormaster completed remote builds in B78655: Diff 191268.Mon, Nov 2, 3:19 AM

nice catch! bz, what do you think?

Adding @dumbbell as msix will change behaviour for amdgpu I believe; msi is indeed ath11k only currently. I'll deal with this as soon as I have stable internet again (as one notices as the submit didn't work the first time).

I'd suggest to reduce it to this.
The ath11k explanation in the commit message is for ath11k but not generic LinuxKPI. There's a further issue if the commit message is correct to be dealt with as the native PCI stack, I believe tracks MSI state (also for resume) and may not be able to do so?

I removed the comment as we generally don't explain fields in details; the information is in the commit message.
I also moved the lines further down to not interfere with the block the comment above says we do.

Author:     Quentin ThÃbault <quentin.thebault@defenso.fr>
AuthorDate: Mon Nov 2 21:43:24 2026 +0000
Commit:     Bjoern A. Zeeb <bz@FreeBSD.org>
CommitDate: Mon Nov 2 21:45:19 2026 +0000

    LinuxKPI: set pci_dev msi_cap and msix_cap
    
    Linux drivers find their MSI and MSI-X registers through pdev->msi_cap and
    pdev->msix_cap, which hold where those capabilities start in PCI config
    space.  LinuxKPI never set them, so they stayed 0, and every access meant
    for the MSI registers went to the start of config space instead.
    
    Drivers using these fields, e.g. ath11k and amdgpu, are affected.
    
    Fill in both fields from the capability offsets that the native PCI code
    already records.
    
    Sponsored by:   Defenso
    Signed-off-by:  Quentin ThÃbault <quentin.thebault@defenso.fr>
    Reviewed by:    bz
    MFC after:      3 days
    Differential Revision: https://reviews.freebsd.org/D61125

diff --git sys/compat/linuxkpi/common/src/linux_pci.c sys/compat/linuxkpi/common/src/linux_pci.c
index bd51082fb4d1..e19a12c295e3 100644
--- sys/compat/linuxkpi/common/src/linux_pci.c
+++ sys/compat/linuxkpi/common/src/linux_pci.c
@@ -521,6 +521,8 @@ lkpi_pci_dev_init_common(device_t dev, struct pci_dev *pdev)
                 */
                pdev->bus->self = pdev;
        }
+       pdev->msi_cap = dinfo->cfg.msi.msi_location;
+       pdev->msix_cap = dinfo->cfg.msix.msix_location;
        pdev->dev.bsddev = dev;
        pdev->dev.parent = &linux_root_device;