KVM: VMX: Support for NMI task gates

Properly set GUEST_INTR_STATE_NMI and reset nmi_injected when a
task-switch vmexit happened due to a task gate being used for handling
NMIs. Also avoid the false warning about valid vectoring info in
kvm_handle_exit.

Based on original patch by Gleb Natapov.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 15 insertions, 3 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 81cf12b8d12a..8d0fc68fd4ec 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2832,6 +2832,7 @@ static int handle_apic_access(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 
 static int handle_task_switch(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 {
+        struct vcpu_vmx *vmx = to_vmx(vcpu);
         unsigned long exit_qualification;
         u16 tss_selector;
         int reason;
@@ -2839,6 +2840,15 @@ static int handle_task_switch(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
         exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
 
         reason = (u32)exit_qualification >> 30;
+        if (reason == TASK_SWITCH_GATE && vmx->vcpu.arch.nmi_injected &&
+            (vmx->idt_vectoring_info & VECTORING_INFO_VALID_MASK) &&
+            (vmx->idt_vectoring_info & VECTORING_INFO_TYPE_MASK)
+            == INTR_TYPE_NMI_INTR) {
+                vcpu->arch.nmi_injected = false;
+                if (cpu_has_virtual_nmis())
+                        vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO,
+                                      GUEST_INTR_STATE_NMI);
+        }
         tss_selector = exit_qualification;
 
         return kvm_task_switch(vcpu, tss_selector, reason);
@@ -3012,9 +3022,11 @@ static int kvm_handle_exit(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu)
 
         if ((vectoring_info & VECTORING_INFO_VALID_MASK) &&
                         (exit_reason != EXIT_REASON_EXCEPTION_NMI &&
-                        exit_reason != EXIT_REASON_EPT_VIOLATION))
-                printk(KERN_WARNING "%s: unexpected, valid vectoring info and "
-                       "exit reason is 0x%x\n", __func__, exit_reason);
+                        exit_reason != EXIT_REASON_EPT_VIOLATION &&
+                        exit_reason != EXIT_REASON_TASK_SWITCH))
+                printk(KERN_WARNING "%s: unexpected, valid vectoring info "
+                       "(0x%x) and exit reason is 0x%x\n",
+                       __func__, vectoring_info, exit_reason);
         if (exit_reason < kvm_vmx_max_exit_handlers
             && kvm_vmx_exit_handlers[exit_reason])
                 return kvm_vmx_exit_handlers[exit_reason](vcpu, kvm_run);