From: dann frazier <dann.frazier@canonical.com>
To: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>,
Mark Brown <broonie@kernel.org>,
linux-arm-kernel@lists.infradead.org,
Marc Zyngier <maz@kernel.org>,
Mark Rutland <mark.rutland@arm.com>
Subject: [PATCH] arm64: Restore forced disabling of KPTI on ThunderX
Date: Wed, 22 Sep 2021 07:59:24 -0600 [thread overview]
Message-ID: <20210922135924.3109291-1-dann.frazier@canonical.com> (raw)
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")
Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: stable@vger.kernel.org # 5.13+
Signed-off-by: dann frazier <dann.frazier@canonical.com>
---
arch/arm64/kernel/cpufeature.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index f8a3067d10c6..7275b49034f3 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1528,7 +1528,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
* ThunderX leads to apparent I-cache corruption of kernel text, which
* ends as well as you might imagine. Don't even try.
*/
- 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;
}
--
2.33.0
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next reply other threads:[~2021-09-22 14:07 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-22 13:59 dann frazier [this message]
2021-09-22 14:11 ` [PATCH] arm64: Restore forced disabling of KPTI on ThunderX Mark Brown
2021-09-22 18:59 ` Marc Zyngier
2021-09-23 9:41 ` Suzuki K Poulose
2021-09-23 14:45 ` dann frazier
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