This is a note to let you know that I've just added the patch titled
[Variant 3/Meltdown] arm64: Turn on KPTI only on CPUs that need it
to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: arm64-turn-on-kpti-only-on-cpus-that-need-it.patch and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From foo@baz Wed Feb 14 14:44:54 CET 2018
From: Jayachandran C jnair@caviumnetworks.com Date: Fri, 19 Jan 2018 04:22:48 -0800 Subject: [Variant 3/Meltdown] arm64: Turn on KPTI only on CPUs that need it
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);
Patches currently in stable-queue which might be from jnair@caviumnetworks.com are
queue-4.14/arm64-turn-on-kpti-only-on-cpus-that-need-it.patch queue-4.14/arm64-branch-predictor-hardening-for-cavium-thunderx2.patch queue-4.14/arm64-cputype-add-midr-values-for-cavium-thunderx2-cpus.patch