From mboxrd@z Thu Jan 1 00:00:00 1970 From: jnair@caviumnetworks.com (Jayachandran C) Date: Fri, 19 Jan 2018 04:22:48 -0800 Subject: [PATCH v3 2/2] arm64: Turn on KPTI only on CPUs that need it In-Reply-To: <1516364568-95577-1-git-send-email-jnair@caviumnetworks.com> References: <20180118135354.GB20783@arm.com> <1516364568-95577-1-git-send-email-jnair@caviumnetworks.com> Message-ID: <1516364568-95577-2-git-send-email-jnair@caviumnetworks.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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. Signed-off-by: Jayachandran C --- arch/arm64/kernel/cpufeature.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 647d44b..fb698ca 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -866,6 +866,13 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, 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); -- 2.7.4