Patch "[Variant 3/Meltdown] arm64: Force KPTI to be disabled on Cavium ThunderX" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

[Variant 3/Meltdown] arm64: Force KPTI to be disabled on Cavium ThunderX

to the 4.14-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-force-kpti-to-be-disabled-on-cavium-thunderx.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 <[email protected]> know about it.

From: Marc Zyngier <[email protected]>
Date: Mon, 29 Jan 2018 11:59:56 +0000
Subject: [Variant 3/Meltdown] arm64: Force KPTI to be disabled on Cavium ThunderX

From: Marc Zyngier <[email protected]>

Commit 6dc52b15c4a4 upstream.

Cavium ThunderX's erratum 27456 results in a corruption of icache entries that are loaded from memory that is mapped as non-global (i.e. ASID-tagged).

As KPTI is based on memory being mapped non-global, let's prevent it from kicking in if this erratum is detected.

---
 arch/arm64/kernel/cpufeature.c |   17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

@@ -803,12 +803,23 @@ static int __kpti_forced; /* 0: not forc
 static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
 				int __unused)
 {
+	char const *str = "command line option";
 	u64 pfr0 = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1);
 
-	/* Forced on command line? */
+	/*
+	 * For reasons that aren't entirely clear, enabling KPTI on Cavium
+	 * ThunderX leads to apparent I-cache corruption of kernel text, which
+	 * ends as well as you might imagine. Don't even try.
+	 */
+	if (cpus_have_const_cap(ARM64_WORKAROUND_CAVIUM_27456)) {
+		str = "ARM64_WORKAROUND_CAVIUM_27456";
+		__kpti_forced = -1;
+	}
+
+	/* Forced? */
 	if (__kpti_forced) {
-		pr_info_once("kernel page table isolation forced %s by command line option\n",
-			     __kpti_forced > 0 ? "ON" : "OFF");
+		pr_info_once("kernel page table isolation forced %s by %s\n",
+			     __kpti_forced > 0 ? "ON" : "OFF", str);
 		return __kpti_forced > 0;
 	}
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/arm-arm64-smccc-make-function-identifiers-an-unsigned-quantity.patch queue-4.14/arm64-move-bp-hardening-to-check_and_switch_context.patch queue-4.14/arm-arm64-kvm-advertise-smccc-v1.1.patch queue-4.14/arm64-move-post_ttbr_update_workaround-to-c-code.patch queue-4.14/firmware-psci-expose-psci-conduit.patch queue-4.14/arm64-force-kpti-to-be-disabled-on-cavium-thunderx.patch queue-4.14/arm64-entry-apply-bp-hardening-for-high-priority-synchronous-exceptions.patch queue-4.14/arm64-kpti-fix-the-interaction-between-asid-switching-and-software-pan.patch queue-4.14/firmware-psci-expose-smccc-version-through-psci_ops.patch queue-4.14/arm64-implement-branch-predictor-hardening-for-affected-cortex-a-cpus.patch queue-4.14/arm-arm64-kvm-add-psci_version-helper.patch queue-4.14/arm64-kill-psci_get_version-as-a-variant-2-workaround.patch queue-4.14/arm64-entry-apply-bp-hardening-for-suspicious-interrupts-from-el0.patch queue-4.14/arm64-capabilities-handle-duplicate-entries-for-a-capability.patch queue-4.14/arm64-add-arm_smccc_arch_workaround_1-bp-hardening-support.patch queue-4.14/arm-arm64-kvm-turn-kvm_psci_version-into-a-static-inline.patch queue-4.14/arm-arm64-kvm-implement-psci-1.0-support.patch queue-4.14/arm64-kvm-add-smccc_arch_workaround_1-fast-handling.patch queue-4.14/arm64-kvm-report-smccc_arch_workaround_1-bp-hardening-support.patch queue-4.14/arm-arm64-smccc-implement-smccc-v1.1-inline-primitive.patch queue-4.14/arm64-idmap-use-awx-flags-for-.idmap.text-.pushsection-directives.patch queue-4.14/arm64-kvm-make-psci_version-a-fast-path.patch queue-4.14/arm64-cpufeature-__this_cpu_has_cap-shouldn-t-stop-early.patch queue-4.14/arm64-kpti-add-enable-callback-to-remap-swapper-using-ng-mappings.patch queue-4.14/arm-arm64-kvm-consolidate-the-psci-include-files.patch queue-4.14/arm64-add-skeleton-to-harden-the-branch-predictor-against-aliasing-attacks.patch queue-4.14/arm-arm64-kvm-add-smccc-accessors-to-psci-code.patch queue-4.14/arm64-kvm-use-per-cpu-vector-when-bp-hardening-is-enabled.patch queue-4.14/arm64-kvm-increment-pc-after-handling-an-smc-trap.patch