| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.14 049/195] [Variant 3/Meltdown] arm64: Turn on KPTI only on CPUs that need it | Date | Thu, 15 Feb 2018 16:15:40 +0100 |
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4.14-stable review patch. If anyone has any objections, please let me know.
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From: Jayachandran C <jnair@caviumnetworks.com>
Commit 0ba2e29c7fc1 upstream.
Whitelist Broadcom Vulcan/Cavium ThunderX2 processors in unmap_kernel_at_el0(). These CPUs are not vulnerable to CVE-2017-5754 and do not need KPTI when KASLR is off.
Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Jayachandran C <jnair@caviumnetworks.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- arch/arm64/kernel/cpufeature.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -816,6 +816,13 @@ static bool unmap_kernel_at_el0(const st if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) return true; + /* Don't force KPTI for CPUs that are not vulnerable */ + switch (read_cpuid_id() & MIDR_CPU_MODEL_MASK) { + case MIDR_CAVIUM_THUNDERX2: + case MIDR_BRCM_VULCAN: + return false; + } + /* Defer to CPU feature registers */ return !cpuid_feature_extract_unsigned_field(pfr0, ID_AA64PFR0_CSV3_SHIFT);
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