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@kernel.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);