iommu/amd: Fix false positive in SB IOAPIC IVRS validation

The check_ioapic_information() function is designed to prevent boot hangs
by ensuring the Southbridge (SB) IOAPIC is properly mapped in the IVRS
table before enabling Interrupt Remapping.

Currently, this check passes if *any* enumerated IOAPIC matches the
expected SB IOAPIC device ID. If a buggy BIOS incorrectly assigns the
SB IOAPIC's device ID to a secondary IOAPIC in the IVRS, while scrambling
the true SB IOAPIC's mapping, the check hits a false positive and
succeeds.

This erroneously enables Interrupt Remapping. Consequently, the IOMMU
blocks unmapped interrupts from the actual SB IOAPIC, dropping the system
timer and leading to a silent kernel boot hang.

Tighten the validation to verify the device ID specifically against the SB
IOAPIC by matching their APIC IDs first. This prevents the validation
check from being bypassed via device ID aliasing.

Fixes: c2ff5cf5294b ("iommu/amd: Work around wrong IOAPIC device-id in IVRS table")
Signed-off-by: Wei Wang <wei.w.wang@hotmail.com>
Tested-by: Yongwei Xu <xuyongwei@open-hieco.net>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

0 files changed, 0 insertions, 0 deletions