KVM: MMU: handle invalid root_hpa at __direct_map

It is possible for __direct_map to be called on invalid root_hpa
(-1), two examples:

1) try_async_pf -> can_do_async_pf
    -> vmx_interrupt_allowed -> nested_vmx_vmexit
2) vmx_handle_exit -> vmx_interrupt_allowed -> nested_vmx_vmexit

Then to load_vmcs12_host_state and kvm_mmu_reset_context.

Check for this possibility, let fault exception be regenerated.

BZ: https://bugzilla.redhat.com/show_bug.cgi?id=924916

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 40772ef0f2b1..31a570287fcc 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2659,6 +2659,9 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write,
         int emulate = 0;
         gfn_t pseudo_gfn;
 
+        if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
+                return 0;
+
         for_each_shadow_entry(vcpu, (u64)gfn << PAGE_SHIFT, iterator) {
                 if (iterator.level == level) {
                         mmu_set_spte(vcpu, iterator.sptep, ACC_ALL,