[Xen-changelog] [xen stable-4.1] vmx: fix handling of NMI VMEXIT.

[patchbot@xxxxxxx]

commit 677c9126023e79cb8e0a74bc002bd7af06b53214
Author:     Tim Deegan <tim@xxxxxxx>
AuthorDate: Tue Mar 12 16:22:03 2013 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Mar 12 16:22:03 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 918c624..e9f1323 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2154,6 +2154,13 @@ 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);
@@ -2327,7 +2334,7 @@ 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 dd62276..a7ce078 100644
--- a/xen/arch/x86/x86_32/entry.S
+++ b/xen/arch/x86/x86_32/entry.S
@@ -624,6 +624,14 @@ 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
@@ -637,7 +645,7 @@ 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 be8a0c5..bc75041 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -648,6 +648,22 @@ 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 ad91c55..2662308 100644
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -587,6 +587,8 @@ DECLARE_TRAP_HANDLER(alignment_check);
 DECLARE_TRAP_HANDLER(spurious_interrupt_bug);
 #undef DECLARE_TRAP_HANDLER
 
+void enable_nmis(void);
+
 int cpuid_hypervisor_leaves( uint32_t idx, uint32_t sub_idx,
           uint32_t *eax, uint32_t *ebx, uint32_t *ecx, uint32_t *edx);
 int rdmsr_hypervisor_regs(uint32_t idx, uint64_t *val);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.1

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