4.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: Jayachandran C <[email protected]> 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 <[email protected]> Signed-off-by: Jayachandran C <[email protected]> Signed-off-by: Catalin Marinas <[email protected]> Signed-off-by: Will Deacon <[email protected]> Signed-off-by: Ard Biesheuvel <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- 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);
