[3.19.y-ckt stable] Patch "arm64: KVM: Add workaround for Cortex-A57 erratum 834220" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    arm64: KVM: Add workaround for Cortex-A57 erratum 834220

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From fcf70c81f42f39a6b0120bc7e713dd2d337c6449 Mon Sep 17 00:00:00 2001
From: Marc Zyngier <marc.zyngier at arm.com>
Date: Mon, 16 Nov 2015 10:28:18 +0000
Subject: arm64: KVM: Add workaround for Cortex-A57 erratum 834220

commit 498cd5c32be6e32bc0f8efcad48ab094bb2bfdf3 upstream.

Cortex-A57 parts up to r1p2 can misreport Stage 2 translation faults
when a Stage 1 permission fault or device alignment fault should
have been reported.

This patch implements the workaround (which is to validate that the
Stage-1 translation actually succeeds) by using code patching.

Reviewed-by: Will Deacon <will.deacon at arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
[ kamal: backport to 3.19-stable: context ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/arm64/Kconfig                  | 21 +++++++++++++++++++++
 arch/arm64/include/asm/cpufeature.h |  3 ++-
 arch/arm64/kernel/cpu_errata.c      |  9 +++++++++
 arch/arm64/kvm/hyp.S                |  6 ++++++
 4 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 67f5ba5..128ea92 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -310,6 +310,27 @@ config ARM64_ERRATUM_832075

 	  If unsure, say Y.

+config ARM64_ERRATUM_834220
+	bool "Cortex-A57: 834220: Stage 2 translation fault might be incorrectly reported in presence of a Stage 1 fault"
+	depends on KVM
+	default y
+	help
+	  This option adds an alternative code sequence to work around ARM
+	  erratum 834220 on Cortex-A57 parts up to r1p2.
+
+	  Affected Cortex-A57 parts might report a Stage 2 translation
+	  fault as the result of a Stage 1 fault for load crossing a
+	  page boundary when there is a permission or device memory
+	  alignment fault at Stage 1 and a translation fault at Stage 2.
+
+	  The workaround is to verify that the Stage 1 translation
+	  doesn't generate a fault before handling the Stage 2 fault.
+	  Please note that this does not necessarily enable the workaround,
+	  as it depends on the alternative framework, which will only patch
+	  the kernel if an affected CPU is detected.
+
+	  If unsure, say Y.
+
 config ARM64_ERRATUM_845719
 	bool "Cortex-A53: 845719: a load might read incorrect data"
 	depends on COMPAT
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 5fe4bef..8a90489 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -24,8 +24,9 @@
 #define ARM64_WORKAROUND_CLEAN_CACHE		0
 #define ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE	1
 #define ARM64_WORKAROUND_845719			2
+#define ARM64_WORKAROUND_834220			3

-#define ARM64_NCAPS				3
+#define ARM64_NCAPS				4

 #ifndef __ASSEMBLY__

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index ad6d523..40fe97e 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -92,6 +92,15 @@ struct arm64_cpu_capabilities arm64_errata[] = {
 			   (1 << MIDR_VARIANT_SHIFT) | 2),
 	},
 #endif
+#ifdef CONFIG_ARM64_ERRATUM_834220
+	{
+	/* Cortex-A57 r0p0 - r1p2 */
+		.desc = "ARM erratum 834220",
+		.capability = ARM64_WORKAROUND_834220,
+		MIDR_RANGE(MIDR_CORTEX_A57, 0x00,
+			   (1 << MIDR_VARIANT_SHIFT) | 2),
+	},
+#endif
 #ifdef CONFIG_ARM64_ERRATUM_845719
 	{
 	/* Cortex-A53 r0p[01234] */
diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index 0a2ff0f..8fc281c 100644
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -1187,9 +1187,15 @@ el1_trap:
 	b.ne	1f		// Not an abort we care about

 	/* This is an abort. Check for permission fault */
+alternative_if_not ARM64_WORKAROUND_834220
 	and	x2, x1, #ESR_EL2_FSC_TYPE
 	cmp	x2, #FSC_PERM
 	b.ne	1f		// Not a permission fault
+alternative_else
+	nop			// Use the permission fault path to
+	nop			// check for a valid S1 translation,
+	nop			// regardless of the ESR value.
+alternative_endif

 	/*
 	 * Check for Stage-1 page table walk, which is guaranteed
--
1.9.1