Re: [PATCH] iommu/amd: Skip non-IVMD entries when parsing IVRS memory definitions

[Vasant Hegde]

On 10/18/2026 1:15 PM, Akshay Jindal wrote:
> init_memory_definitions() walks every top-level subtable including the
> IVHD blocks (type 0x10/0x11/0x40) in the IVRS ACPI table. It interprets
> each one as a 'struct ivmd_header', solely on m->flags, without first
> checking that the subtable's type actually is one of the IVMD types
> (ACPI_IVMD_TYPE, ACPI_IVMD_TYPE_ALL, ACPI_IVMD_TYPE_RANGE).
> 
>     if (m->flags & (IVMD_FLAG_UNITY_MAP | IVMD_FLAG_EXCL_RANGE))
>             init_unity_map_range(m, table);
> 
> IVMD_FLAG_UNITY_MAP (0x01) occupies the same bit position as the IVHD
> flags field's HtTunEn bit. Unlike real hardware, QEMU's AMD IOMMU
> emulation sets HtTunEn unconditionally (flags=0xD1 for type 0x10,
> 0x11 for type 0x11), so every QEMU-emitted IVHD block is misidentified
> as a unity-map/exclusion-range IVMD entry, which subsequently results
> in the creation of a bogus pci segment. Eg:
> 
>     AMD-Vi: PCI segment : 0x4000, last bdf : 0x0000
> 
> Fix by checking the subtable's type before treating it as IVMD.
> 
> Fixes: be2a022c0dd0 ("x86, AMD IOMMU: add functions to parse IOMMU memory mapping requirements for devices")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Akshay Jindal <Akshay.Jindal@xxxxxxx>

Thanks. Queued for rc.

-Vasant