linux-kernel - [PATCH 4.9 47/59] ARM: KVM: invalidate icache on guest exit for Cortex-A15

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Date:   Wed, 21 Nov 2018 20:07:02 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Marc Zyngier <marc.zyngier@....com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Tony Lindgren <tony@...mide.com>,
        "David A. Long" <dave.long@...aro.org>
Subject: [PATCH 4.9 47/59] ARM: KVM: invalidate icache on guest exit for Cortex-A15

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marc Zyngier <marc.zyngier@....com>

Commit 0c47ac8cd157727e7a532d665d6fb1b5fd333977 upstream.

In order to avoid aliasing attacks against the branch predictor
on Cortex-A15, let's invalidate the BTB on guest exit, which can
only be done by invalidating the icache (with ACTLR[0] being set).

We use the same hack as for A12/A17 to perform the vector decoding.

Signed-off-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
Boot-tested-by: Tony Lindgren <tony@...mide.com>
Reviewed-by: Tony Lindgren <tony@...mide.com>
Signed-off-by: David A. Long <dave.long@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm/include/asm/kvm_mmu.h |    5 +++++
 arch/arm/kvm/hyp/hyp-entry.S   |   24 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+)

--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -257,6 +257,11 @@ static inline void *kvm_get_hyp_vector(v
 		return kvm_ksym_ref(__kvm_hyp_vector_bp_inv);
 	}
 
+	case ARM_CPU_PART_CORTEX_A15:
+	{
+		extern char __kvm_hyp_vector_ic_inv[];
+		return kvm_ksym_ref(__kvm_hyp_vector_ic_inv);
+	}
 #endif
 	default:
 	{
--- a/arch/arm/kvm/hyp/hyp-entry.S
+++ b/arch/arm/kvm/hyp/hyp-entry.S
@@ -73,6 +73,28 @@ __kvm_hyp_vector:
 
 #ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
 	.align 5
+__kvm_hyp_vector_ic_inv:
+	.global __kvm_hyp_vector_ic_inv
+
+	/*
+	 * We encode the exception entry in the bottom 3 bits of
+	 * SP, and we have to guarantee to be 8 bytes aligned.
+	 */
+	W(add)	sp, sp, #1	/* Reset 	  7 */
+	W(add)	sp, sp, #1	/* Undef	  6 */
+	W(add)	sp, sp, #1	/* Syscall	  5 */
+	W(add)	sp, sp, #1	/* Prefetch abort 4 */
+	W(add)	sp, sp, #1	/* Data abort	  3 */
+	W(add)	sp, sp, #1	/* HVC		  2 */
+	W(add)	sp, sp, #1	/* IRQ		  1 */
+	W(nop)			/* FIQ		  0 */
+
+	mcr	p15, 0, r0, c7, c5, 0	/* ICIALLU */
+	isb
+
+	b	decode_vectors
+
+	.align 5
 __kvm_hyp_vector_bp_inv:
 	.global __kvm_hyp_vector_bp_inv
 
@@ -92,6 +114,8 @@ __kvm_hyp_vector_bp_inv:
 	mcr	p15, 0, r0, c7, c5, 6	/* BPIALL */
 	isb
 
+decode_vectors:
+
 #ifdef CONFIG_THUMB2_KERNEL
 	/*
 	 * Yet another silly hack: Use VPIDR as a temp register.