RE: [PATCH v3 2/5] iommu/vt-d: Fix NULL domain on device release

[Tian, Kevin]

> From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Tuesday, March 5, 2024 9:33 AM
> 
> In the kdump kernel, the IOMMU operates in deferred_attach mode. In this
> mode, info->domain may not yet be assigned by the time the release_device
> function is called. It leads to the following crash in the crash kernel:
> 
>     BUG: kernel NULL pointer dereference, address: 000000000000003c
>     ...
>     RIP: 0010:do_raw_spin_lock+0xa/0xa0
>     ...
>     _raw_spin_lock_irqsave+0x1b/0x30
>     intel_iommu_release_device+0x96/0x170
>     iommu_deinit_device+0x39/0xf0
>     __iommu_group_remove_device+0xa0/0xd0
>     iommu_bus_notifier+0x55/0xb0
>     notifier_call_chain+0x5a/0xd0
>     blocking_notifier_call_chain+0x41/0x60
>     bus_notify+0x34/0x50
>     device_del+0x269/0x3d0
>     pci_remove_bus_device+0x77/0x100
>     p2sb_bar+0xae/0x1d0
>     ...
>     i801_probe+0x423/0x740
> 
> Use the release_domain mechanism to fix it. The scalable mode context
> entry which is not part of release_domain should be cleared in
> release_device().
> 
> Fixes: 586081d3f6b1 ("iommu/vt-d: Remove DEFER_DEVICE_DOMAIN_INFO")
> Reported-by: Eric Badger <ebadger@xxxxxxxxxxxxxxx>
> Closes: https://lore.kernel.org/r/20240113181713.1817855-1-
> ebadger@xxxxxxxxxxxxxxx
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>