[PATCH v2 2/4] VMX: Fix the mistake of exception execution

[Xudong Hao <xudong.hao@intel.com>]

Fix the mistake for debug exception(#DB), overflow exception(#OF) and
INT3(#BP), INTn instruction emulation.

Add inslen field in struct hvm_trap. According to instruction length,
to distinguish INT3 is generated by opcode 'CC' or 'CD ib =3',
so do INTO and #DB(debug exception).

Note:
 * For INTn (CD ib), it should use type 4 (software interrupt).

 * For INT3 (CC; NOT CD ib with ib=3) and INTO (CE; NOT CD ib with ib=4),
   it should use type 6 (software exception).

 * For other exceptions (#DE, #DB, #BR, #UD, #NM, #TS, #NP, #SS, #GP, #PF, #MF,
   #AC, #MC, and #XM), it should use type 3 (hardware exception).

 * In the unlikely event that you are emulating the undocumented opcode F1
   (informally called INT1 or ICEBP), it would use type 5 (privileged software
   exception).

Signed-off-by: Xudong Hao <xudong.hao@intel.com>
Signed-off-by: Eddie Dong <eddie.dong@intel.com>
Signed-off-by: Xiantao Zhang <xiantao.zhang@intel.com>
---
 xen/arch/x86/hvm/vmx/vmx.c    |   43 ++++++++++++++++++++++++++++++++++++++++-
 xen/include/asm-x86/hvm/hvm.h |    2 +
 2 files changed, 44 insertions(+), 1 deletions(-)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index c96d18b..cf08a11 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -1381,6 +1381,19 @@ void vmx_inject_nmi(void)
                            HVM_DELIVER_NO_ERROR_CODE);
 }
 
+/*
+ * Generate the virtual event to guest.
+ * NOTE:
+ *    This is for processor execution generated exceptions,
+ * and handle #DB hardware exception and all software 
+ * exception/interrupt, which include:
+ *  - INT 3(CC), INTO (CE) instruction emulation, which should
+ *    use X86_EVENTTYPE_SW_EXCEPTION;
+ *  - INT nn (CD nn) instruction emulation, which should use
+ *    X86_EVENTTYPE_SW_INTERRUPT as interrupt type;
+ *  - opcode 0xf1 generated #DB should use privileged software
+ *    exception.
+ */
 static void vmx_inject_trap(struct hvm_trap *trap)
 {
     unsigned long intr_info;
@@ -1399,6 +1412,12 @@ static void vmx_inject_trap(struct hvm_trap *trap)
     switch ( _trap.vector )
     {
     case TRAP_debug:
+        _trap.type = X86_EVENTTYPE_HW_EXCEPTION;
+        if ( _trap.inslen != 1 ) {
+            _trap.type = X86_EVENTTYPE_PRI_SW_EXCEPTION;  /* opcode 0xf1 */
+            __vmwrite(VM_ENTRY_INSTRUCTION_LEN, _trap.inslen);
+        }
+
         if ( guest_cpu_user_regs()->eflags & X86_EFLAGS_TF )
         {
             __restore_debug_registers(curr);
@@ -1414,6 +1433,27 @@ static void vmx_inject_trap(struct hvm_trap *trap)
             domain_pause_for_debugger();
             return;
         }
+        _trap.type = X86_EVENTTYPE_SW_EXCEPTION;  /* CC */
+        if ( _trap.inslen != 1 )
+            _trap.type = X86_EVENTTYPE_SW_INTERRUPT;  /* CD ib with ib=3 */
+        __vmwrite(VM_ENTRY_INSTRUCTION_LEN, _trap.inslen);
+        break;
+
+    case TRAP_overflow:
+        _trap.type = X86_EVENTTYPE_SW_EXCEPTION;  /* CE */
+        if ( _trap.inslen != 1 )
+            _trap.type = X86_EVENTTYPE_SW_INTERRUPT;  /* CD ib with ib=4 */
+        __vmwrite(VM_ENTRY_INSTRUCTION_LEN, _trap.inslen);
+        break;
+
+    default:
+        if ( _trap.vector > TRAP_last_reserved ) /* int imm8 */
+        {
+            _trap.type = X86_EVENTTYPE_SW_INTERRUPT;
+            __vmwrite(VM_ENTRY_INSTRUCTION_LEN, _trap.inslen);
+        }
+        break;
+
     }
 
     if ( unlikely(intr_info & INTR_INFO_VALID_MASK) &&
@@ -2424,7 +2464,8 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
                     struct hvm_trap trap = {
                         .vector = TRAP_int3,
                         .type = X86_EVENTTYPE_SW_EXCEPTION,
-                        .error_code = HVM_DELIVER_NO_ERROR_CODE
+                        .error_code = HVM_DELIVER_NO_ERROR_CODE,
+                        .inslen = __vmread(VM_EXIT_INSTRUCTION_LEN)
                     };
                     hvm_inject_trap(&trap);
                     break;
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index 65f7e20..a3d8bf1 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -76,6 +76,7 @@ struct hvm_trap {
     unsigned int  type;         /* X86_EVENTTYPE_* */
     int           error_code;   /* HVM_DELIVER_NO_ERROR_CODE if n/a */
     unsigned long cr2;          /* Only for TRAP_page_fault h/w exception */
+    int           inslen;       /* Instruction length */ 
 };
 
 /*
@@ -375,6 +376,7 @@ static inline int hvm_do_pmu_interrupt(struct cpu_user_regs *regs)
 #define X86_EVENTTYPE_NMI                   2    /* NMI                */
 #define X86_EVENTTYPE_HW_EXCEPTION          3    /* hardware exception */
 #define X86_EVENTTYPE_SW_INTERRUPT          4    /* software interrupt */
+#define X86_EVENTTYPE_PRI_SW_EXCEPTION      5    /* privileged software exception */
 #define X86_EVENTTYPE_SW_EXCEPTION          6    /* software exception */
 
 int hvm_event_needs_reinjection(uint8_t type, uint8_t vector);
-- 
1.5.5