linux-kernel - [PATCH 06/16] KVM: arm64: Force a full unmap on vpcu reinit

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Message-Id: <20210715163159.1480168-7-maz@kernel.org>
Date:   Thu, 15 Jul 2021 17:31:49 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     will@...nel.org, qperret@...gle.com, dbrazdil@...gle.com,
        Srivatsa Vaddagiri <vatsa@...eaurora.org>,
        Shanker R Donthineni <sdonthineni@...dia.com>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        kernel-team@...roid.com
Subject: [PATCH 06/16] KVM: arm64: Force a full unmap on vpcu reinit

As we now keep information in the S2PT, we must be careful not
to keep it across a VM reboot, which could otherwise lead to
interesting problems.

Make sure that the S2 is completely discarded on reset of
a vcpu, and remove the flag that enforces the MMIO check.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 arch/arm64/kvm/arm.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 97ab1512c44f..b0d2225190d2 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1096,12 +1096,18 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
 	 * ensuring that the data side is always coherent. We still
 	 * need to invalidate the I-cache though, as FWB does *not*
 	 * imply CTR_EL0.DIC.
+	 *
+	 * If the MMIO guard was enabled, we pay the price of a full
+	 * unmap to get back to a sane state (and clear the flag).
 	 */
 	if (vcpu->arch.has_run_once) {
-		if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB))
+		if (!cpus_have_final_cap(ARM64_HAS_STAGE2_FWB) ||
+		    test_bit(KVM_ARCH_FLAG_MMIO_GUARD, &vcpu->kvm->arch.flags))
 			stage2_unmap_vm(vcpu->kvm);
 		else
 			icache_inval_all_pou();
+
+		clear_bit(KVM_ARCH_FLAG_MMIO_GUARD, &vcpu->kvm->arch.flags);
 	}
 
 	vcpu_reset_hcr(vcpu);
-- 
2.30.2