[Xen-changelog] [xen stable-4.2] vmx: fix handling of NMI VMEXIT.

[patchbot@xxxxxxx]

commit d0058d3973c3f699b09c45ae20c93156e28192c9
Author:     Tim Deegan <tim@xxxxxxx>
AuthorDate: Tue Mar 12 16:10:23 2013 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Mar 12 16:10:23 2013 +0100

    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@xxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    master changeset: 7dd3b06ff031c9a8c727df16c5def2afb382101c
    master date: 2013-02-28 14:00:18 +0000
---
 xen/arch/x86/hvm/vmx/vmx.c      |    9 ++++++++-
 xen/arch/x86/x86_32/entry.S     |   10 +++++++++-
 xen/arch/x86/x86_64/entry.S     |   16 ++++++++++++++++
 xen/include/asm-x86/processor.h |    2 ++
 4 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index ca92b86..de6340d 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2311,6 +2311,13 @@ 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);
@@ -2484,7 +2491,7 @@ 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);
diff --git a/xen/arch/x86/x86_32/entry.S b/xen/arch/x86/x86_32/entry.S
index 2982679..ae7a1b2 100644
--- a/xen/arch/x86/x86_32/entry.S
+++ b/xen/arch/x86/x86_32/entry.S
@@ -621,6 +621,14 @@ ENTRY(machine_check)
         pushl $TRAP_machine_check<<16
         jmp   handle_nmi_mce
 
+/* Enable NMIs.  No special register assumptions. All registers are preserved. 
*/
+ENTRY(enable_nmis)
+        /* Set up stack frame */
+        pushf          # EFLAGS
+        push  %cs      # CS
+        push  $.Lret   # EIP
+        iret           # Disable the hardware NMI latch
+
 ENTRY(setup_vm86_frame)
         mov %ecx,%ds
         mov %ecx,%es
@@ -634,7 +642,7 @@ ENTRY(setup_vm86_frame)
         .endm
         copy_vm86_words
         addl $16,%esp
-        ret
+.Lret:  ret
 
 .section .rodata, "a", @progbits
 
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 997bc94..abc5037 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -643,6 +643,22 @@ ENTRY(machine_check)
         movl  $TRAP_machine_check,4(%rsp)
         jmp   handle_ist_exception
 
+/* Enable NMIs.  No special register assumptions. Only %rax is not preserved. 
*/
+ENTRY(enable_nmis)
+        movq  %rsp, %rax /* Grab RSP before pushing */
+
+        /* Set up stack frame */
+        pushq $0               /* SS */
+        pushq %rax             /* RSP */
+        pushfq                 /* RFLAGS */
+        pushq $__HYPERVISOR_CS /* CS */
+        leaq  1f(%rip),%rax
+        pushq %rax             /* RIP */
+
+        iretq /* Disable the hardware NMI latch */
+1:
+        retq
+
 .section .rodata, "a", @progbits
 
 ENTRY(exception_table)
diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index 7164a50..4ce47eb 100644
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -584,6 +584,8 @@ DECLARE_TRAP_HANDLER(alignment_check);
 DECLARE_TRAP_HANDLER(spurious_interrupt_bug);
 #undef DECLARE_TRAP_HANDLER
 
+void enable_nmis(void);
+
 void syscall_enter(void);
 void sysenter_entry(void);
 void sysenter_eflags_saved(void);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.2

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