linux-kernel - [PATCH 3.16 028/233] kvm: arm/arm64: Force reading uncached stage2 PGD

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Date:   Sat, 09 Sep 2017 22:47:14 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Christoffer Dall" <cdall@...aro.org>,
        "Marc Zyngier" <marc.zyngier@....com>,
        "Suzuki K Poulose" <suzuki.poulose@....com>
Subject: [PATCH 3.16 028/233] kvm: arm/arm64: Force reading uncached
 stage2 PGD

3.16.48-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Suzuki K Poulose <suzuki.poulose@....com>

commit 2952a6070e07ebdd5896f1f5b861acad677caded upstream.

Make sure we don't use a cached value of the KVM stage2 PGD while
resetting the PGD.

Cc: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
Reviewed-by: Christoffer Dall <cdall@...aro.org>
Signed-off-by: Christoffer Dall <cdall@...aro.org>
[bwh: Backported to 3.16:
 - s/READ_ONCE/ACCESS_ONCE/
 - Adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/arm/kvm/mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -643,7 +643,7 @@ void kvm_free_stage2_pgd(struct kvm *kvm
 	spin_lock(&kvm->mmu_lock);
 	if (kvm->arch.pgd) {
 		unmap_stage2_range(kvm, 0, KVM_PHYS_SIZE);
-		pgd = kvm->arch.pgd;
+		pgd = ACCESS_ONCE(kvm->arch.pgd);
 		kvm->arch.pgd = NULL;
 	}
 	spin_unlock(&kvm->mmu_lock);