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| author | dann frazier <dann.frazier@canonical.com> | 2021-09-23 08:50:02 -0600 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2021-09-23 15:59:15 +0100 |
| commit | 22b70e6f2da0a4c8b1421b00cfc3016bc9d4d9d4 (patch) | |
| tree | bbd4e04dcf32a7db7296e56a6d1905389d2c9288 /arch | |
| parent | 0e3dbf765fe22060acbcb8eb8c4d256e655a1247 (diff) | |
| download | linux-22b70e6f2da0a4c8b1421b00cfc3016bc9d4d9d4.tar.bz2 | |
arm64: Restore forced disabling of KPTI on ThunderX
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.
Because all ThunderX implementations have homogeneous CPUs, we can remove
this dependency by just checking the current CPU for the erratum.
Fixes: 0c6c2d3615ef ("arm64: Generate cpucaps.h")
Cc: <stable@vger.kernel.org> # 5.13.x
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210923145002.3394558-1-dann.frazier@canonical.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm64/kernel/cpufeature.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index f8a3067d10c6..6ec7036ef7e1 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -1526,9 +1526,13 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, /* * For reasons that aren't entirely clear, enabling KPTI on Cavium * ThunderX leads to apparent I-cache corruption of kernel text, which - * ends as well as you might imagine. Don't even try. + * ends as well as you might imagine. Don't even try. We cannot rely + * on the cpus_have_*cap() helpers here to detect the CPU erratum + * because cpucap detection order may change. However, since we know + * affected CPUs are always in a homogeneous configuration, it is + * safe to rely on this_cpu_has_cap() here. */ - if (cpus_have_const_cap(ARM64_WORKAROUND_CAVIUM_27456)) { + if (this_cpu_has_cap(ARM64_WORKAROUND_CAVIUM_27456)) { str = "ARM64_WORKAROUND_CAVIUM_27456"; __kpti_forced = -1; } |