Re: [PATCH 1/1] iommu/vt-d: Fix WARN_ON in iommu probe path

[Baolu Lu <baolu.lu@linux.intel.com>]

On 4/7/24 9:14 AM, Lu Baolu wrote:
> Commit 1a75cc710b95 ("iommu/vt-d: Use rbtree to track iommu probed
> devices") adds all devices probed by the iommu driver in a rbtree
> indexed by the source ID of each device. It assumes that each device
> has a unique source ID. This assumption is incorrect and the VT-d
> spec doesn't state this requirement either.
> 
> The reason for using a rbtree to track devices is to look up the device
> with PCI bus and devfunc in the paths of handling ATS invalidation time
> out error and the PRI I/O page faults. Both are PCI ATS feature related.
> 
> Only track the devices that have PCI ATS capabilities in the rbtree to
> avoid unnecessary WARN_ON in the iommu probe path. Otherwise, on some
> platforms below kernel splat will be displayed and the iommu probe results
> in failure.
> 
>   WARNING: CPU: 3 PID: 166 at drivers/iommu/intel/iommu.c:158 intel_iommu_probe_device+0x319/0xd90
>   Call Trace:
>    <TASK>
>    ? __warn+0x7e/0x180
>    ? intel_iommu_probe_device+0x319/0xd90
>    ? report_bug+0x1f8/0x200
>    ? handle_bug+0x3c/0x70
>    ? exc_invalid_op+0x18/0x70
>    ? asm_exc_invalid_op+0x1a/0x20
>    ? intel_iommu_probe_device+0x319/0xd90
>    ? debug_mutex_init+0x37/0x50
>    __iommu_probe_device+0xf2/0x4f0
>    iommu_probe_device+0x22/0x70
>    iommu_bus_notifier+0x1e/0x40
>    notifier_call_chain+0x46/0x150
>    blocking_notifier_call_chain+0x42/0x60
>    bus_notify+0x2f/0x50
>    device_add+0x5ed/0x7e0
>    platform_device_add+0xf5/0x240
>    mfd_add_devices+0x3f9/0x500
>    ? preempt_count_add+0x4c/0xa0
>    ? up_write+0xa2/0x1b0
>    ? __debugfs_create_file+0xe3/0x150
>    intel_lpss_probe+0x49f/0x5b0
>    ? pci_conf1_write+0xa3/0xf0
>    intel_lpss_pci_probe+0xcf/0x110 [intel_lpss_pci]
>    pci_device_probe+0x95/0x120
>    really_probe+0xd9/0x370
>    ? __pfx___driver_attach+0x10/0x10
>    __driver_probe_device+0x73/0x150
>    driver_probe_device+0x19/0xa0
>    __driver_attach+0xb6/0x180
>    ? __pfx___driver_attach+0x10/0x10
>    bus_for_each_dev+0x77/0xd0
>    bus_add_driver+0x114/0x210
>    driver_register+0x5b/0x110
>    ? __pfx_intel_lpss_pci_driver_init+0x10/0x10 [intel_lpss_pci]
>    do_one_initcall+0x57/0x2b0
>    ? kmalloc_trace+0x21e/0x280
>    ? do_init_module+0x1e/0x210
>    do_init_module+0x5f/0x210
>    load_module+0x1d37/0x1fc0
>    ? init_module_from_file+0x86/0xd0
>    init_module_from_file+0x86/0xd0
>    idempotent_init_module+0x17c/0x230
>    __x64_sys_finit_module+0x56/0xb0
>    do_syscall_64+0x6e/0x140
>    entry_SYSCALL_64_after_hwframe+0x71/0x79
> 
> Fixes: 1a75cc710b95 ("iommu/vt-d: Use rbtree to track iommu probed devices")
> Signed-off-by: Lu Baolu<baolu.lu@linux.intel.com>
> ---
>   drivers/iommu/intel/iommu.c | 11 +++++++----
>   1 file changed, 7 insertions(+), 4 deletions(-)

This patch closes a boot bug described here.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10689

I will queue it for v6.9-rc if no objection.

Best regards,
baolu