KVM: x86/mmu: clear MMIO cache when unloading the MMU

For cleanliness, do not leave a stale GVA in the cache after all the roots are
cleared.  In practice, kvm_mmu_load will go through kvm_mmu_sync_roots if
paging is on, and will not use vcpu_match_mmio_gva at all if paging is off.
However, leaving data in the cache might cause bugs in the future.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -5082,6 +5082,7 @@ void kvm_mmu_unload(struct kvm_vcpu *vcpu)
 	WARN_ON(VALID_PAGE(vcpu->arch.root_mmu.root.hpa));
 	kvm_mmu_free_roots(kvm, &vcpu->arch.guest_mmu, KVM_MMU_ROOTS_ALL);
 	WARN_ON(VALID_PAGE(vcpu->arch.guest_mmu.root.hpa));
+	vcpu_clear_mmio_info(vcpu, MMIO_GVA_ANY);
 }
 
 static bool need_remote_flush(u64 old, u64 new)