[PATCH] kvm: x86: get vmcs12 pages before checking pending interrupts

[Oliver Upton <oupton@google.com>]

vmx_guest_apic_has_interrupt implicitly depends on the virtual APIC
page being present + mapped into the kernel address space. Normally,
upon VMLAUNCH/VMRESUME, we get the vmcs12 pages directly. However, if a
live migration were to occur before reaching vcpu_block, the virtual
APIC will not be restored on the target host.

Fix this by getting vmcs12 pages before inspecting the virtual APIC
page.

Cc: kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Oliver Upton <oupton@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
---

 Parent commit: 7c67f54661fc ("KVM: SVM: do not allow VMRUN inside SMM")

 arch/x86/kvm/x86.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8c0b77ac8dc6..edd3b75ad578 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8494,6 +8494,16 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 
 static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu)
 {
+	/*
+	 * We must first get the vmcs12 pages before checking for interrupts
+	 * (done in kvm_arch_vcpu_runnable) in case L1 is using
+	 * virtual-interrupt delivery.
+	 */
+	if (kvm_check_request(KVM_REQ_GET_VMCS12_PAGES, vcpu)) {
+		if (unlikely(!kvm_x86_ops.nested_ops->get_vmcs12_pages(vcpu)))
+			return 0;
+	}
+
 	if (!kvm_arch_vcpu_runnable(vcpu) &&
 	    (!kvm_x86_ops.pre_block || kvm_x86_ops.pre_block(vcpu) == 0)) {
 		srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
-- 
2.26.2.526.g744177e7f7-goog