ANBZ: #6882 iommu/vt-d: Fix kdump kernels boot failure with scalable mode · Pull Request !2341 · anolis/cloud-kernel

bugzilla: https://bugzilla.openanolis.cn/show_bug.cgi?id=6882

The translation table copying code for kdump kernels is currently based
on the extended root/context entry formats of ECS mode defined in older
VT-d v2.5, and doesn't handle the scalable mode formats. This causes
the kexec capture kernel boot failure with DMAR faults if the IOMMU was
enabled in scalable mode by the previous kernel.

The ECS mode has already been deprecated by the VT-d spec since v3.0 and
Intel IOMMU driver doesn't support this mode as there's no real hardware
implementation. Hence this converts ECS checking in copying table code
into scalable mode.

The existing copying code consumes a bit in the context entry as a mark
of copied entry. It needs to work for the old format as well as for the
extended context entries. As it's hard to find such a common bit for both
legacy and scalable mode context entries. This replaces it with a per-
IOMMU bitmap.

Test passed:
1. config kdump as usual. 
2. append intel_iommu=on, sm_on to kernel command line
3. trigger kdump, 
# echo c > /proc/sysrq-trigger
Kdump works.

Help to review and merge

Thanks,
Ethan

类型	指派人员	状态
审查	Guanjun zelindeng Xuchun Shang	已完成 (0/0人)
测试	小龙已测试通过	已完成 (1/1人)

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