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From: Marc Zyngier <maz@kernel.org>
To: linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
Cc: James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	kernel-team@android.com, stable@vger.kernel.org
Subject: [PATCH] KVM: arm64: Fully zero the vcpu state on reset
Date: Wed,  7 Apr 2021 19:13:08 +0100
Message-ID: <20210407181308.2265808-1-maz@kernel.org> (raw)

On vcpu reset, we expect all the registers to be brought back
to their initial state, which happens to be a bunch of zeroes.

However, some recent commit broke this, and is now leaving a bunch
of registers (such as a FP state) with whatever was left by the
guest. My bad.

Just zero the whole vcpu context on reset. It is more than we
strictly need, but at least we won't miss anything. This also
zeroes the __hyp_running_vcpu pointer, which is always NULL
for a vcpu anyway.

Cc: stable@vger.kernel.org
Fixes: e47c2055c68e ("KVM: arm64: Make struct kvm_regs userspace-only")
Signed-off-by: Marc Zyngier <maz@kernel.org>
 arch/arm64/kvm/reset.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index bd354cd45d28..ef1c49a1a3ad 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -240,8 +240,8 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
-	/* Reset core registers */
-	memset(vcpu_gp_regs(vcpu), 0, sizeof(*vcpu_gp_regs(vcpu)));
+	/* Zero all registers */
+	memset(&vcpu->arch.ctxt, 0, sizeof(vcpu->arch.ctxt));
 	vcpu_gp_regs(vcpu)->pstate = pstate;
 	/* Reset system registers */

             reply index

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-07 18:13 Marc Zyngier [this message]
2021-04-08 15:36 ` Alexandru Elisei
2021-04-09 17:18   ` Marc Zyngier

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