vmx: fix handling of NMI VMEXIT.

Call do_nmi() directly and explicitly re-enable NMIs rather than
raising an NMI through the APIC. Since NMIs are disabled after the
VMEXIT, the raised NMI would be blocked until the next IRET
instruction (i.e. the next real interrupt, or after scheduling a PV
guest) and in the meantime the guest will spin taking NMI VMEXITS.

Also, handle NMIs before re-enabling interrupts, since if we handle an
interrupt (and therefore IRET) before calling do_nmi(), we may end up
running the NMI handler with NMIs enabled.

Signed-off-by: Tim Deegan <tim@xen.org>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 53789286cec910de80adfe3db2d5df2c6412e547..04dbefbd2a8c38b36d06cb07964b6304dcf85c44 100644 (file)
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2313,6 +2313,13 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
         vector = intr_info & INTR_INFO_VECTOR_MASK;
         if ( vector == TRAP_machine_check )
             do_machine_check(regs);
+        if ( vector == TRAP_nmi
+             && ((intr_info & INTR_INFO_INTR_TYPE_MASK) ==
+                 (X86_EVENTTYPE_NMI << 8)) )
+        {
+            do_nmi(regs);
+            enable_nmis();
+        }
         break;
     case EXIT_REASON_MCE_DURING_VMENTRY:
         do_machine_check(regs);
@@ -2486,7 +2493,7 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
                  (X86_EVENTTYPE_NMI << 8) )
                 goto exit_and_crash;
             HVMTRACE_0D(NMI);
-            self_nmi(); /* Real NMI, vector 2: normal processing. */
+            /* Already handled above. */
             break;
         case TRAP_machine_check:
             HVMTRACE_0D(MCE);