On Thu, 23 Sep 2021 08:50:02 -0600, dann frazier wrote:

A noted side-effect of commit 0c6c2d3615ef ("arm64: Generate cpucaps.h")
is that cpucaps are now sorted, changing the enumeration order. This
assumed no dependencies between cpucaps, which turned out not to be true
in one case. UNMAP_KERNEL_AT_EL0 currently needs to be processed after
WORKAROUND_CAVIUM_27456. ThunderX systems are incompatible with KPTI, so
unmap_kernel_at_el0() bails if WORKAROUND_CAVIUM_27456 is set. But because
of the sorting, WORKAROUND_CAVIUM_27456 will not yet have been considered
when unmap_kernel_at_el0() checks for it, so the kernel tries to
run w/ KPTI - and quickly falls over.

[...]

Applied to arm64 (for-next/fixes), thanks!

[1/1] arm64: Restore forced disabling of KPTI on ThunderX
      https://git.kernel.org/arm64/c/22b70e6f2da0

-- 
Catalin


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