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 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
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-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Tue Feb 13 17:25:10 CET 2018
From: Jayachandran C <jnair@xxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxx>
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@xxxxxxx>
Signed-off-by: Jayachandran C <jnair@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/kernel/cpufeature.c | 7 +++++++
1 file changed, 7 insertions(+)
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -866,6 +866,13 @@ 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@xxxxxxxxxxxxxxxxxx are
queue-4.15/arm64-turn-on-kpti-only-on-cpus-that-need-it.patch
queue-4.15/arm64-branch-predictor-hardening-for-cavium-thunderx2.patch
queue-4.15/arm64-cputype-add-midr-values-for-cavium-thunderx2-cpus.patch