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arm64: kpti: Whitelist Cortex-A CPUs that don't implement the CSV3 field

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commit 2a355ec25729053bb9a1a89b6c1d1cdd6c3b3fb1 upstream.

While the CSV3 field of the ID_AA64_PFR0 CPU ID register can be checked
to see if a CPU is susceptible to Meltdown and therefore requires kpti
to be enabled, existing CPUs do not implement this field.

We therefore whitelist all unaffected Cortex-A CPUs that do not implement
the CSV3 field.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Niklas Cassel <niklas.cassel@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Will Deacon 2018-12-13 13:47:38 +00:00 committed by Greg Kroah-Hartman
parent aaa800052a
commit fe24ee7832
1 changed files with 5 additions and 0 deletions
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5
arch/arm64/kernel/cpufeature.c
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@ -838,6 +838,11 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
switch (read_cpuid_id() & MIDR_CPU_MODEL_MASK) {
case MIDR_CAVIUM_THUNDERX2:
case MIDR_BRCM_VULCAN:
case MIDR_CORTEX_A53:
case MIDR_CORTEX_A55:
case MIDR_CORTEX_A57:
case MIDR_CORTEX_A72:
case MIDR_CORTEX_A73:
return false;
}