KVM: x86: MOVNTI emulation min opsize is not respected

Commit 3b32004a66e9 ("KVM: x86: movnti minimum op size of 32-bit is not kept")
did not fully fix the minimum operand size of MONTI emulation. Still, MOVNTI
may be mistakenly performed using 16-bit opsize.

This patch add No16 flag to mark an instruction does not support 16-bits
operand size.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index dab9b74..e020fed 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -167,6 +167,7 @@
 #define NoBigReal   ((u64)1 << 50)  /* No big real mode */
 #define PrivUD      ((u64)1 << 51)  /* #UD instead of #GP on CPL > 0 */
 #define NearBranch  ((u64)1 << 52)  /* Near branches */
+#define No16       ((u64)1 << 53)  /* No 16 bit operand */
 
 #define DstXacc     (DstAccLo | SrcAccHi | SrcWrite)
 
@@ -4134,7 +4135,7 @@ static const struct opcode twobyte_table[256] = {
        D(DstReg | SrcMem8 | ModRM | Mov), D(DstReg | SrcMem16 | ModRM | Mov),
        /* 0xC0 - 0xC7 */
        F2bv(DstMem | SrcReg | ModRM | SrcWrite | Lock, em_xadd),
-       N, D(DstMem | SrcReg | ModRM | Mov),
+       N, I(DstMem | SrcReg | ModRM | No16 | Mov, em_mov),
        N, N, N, GD(0, &group9),
        /* 0xC8 - 0xCF */
        X8(I(DstReg, em_bswap)),
@@ -4571,7 +4572,8 @@ done_prefixes:
                return EMULATION_FAILED;
 
        if (unlikely(ctxt->d &
-           (NotImpl|Stack|Op3264|Sse|Mmx|Intercept|CheckPerm|NearBranch))) {
+           (NotImpl|Stack|Op3264|Sse|Mmx|Intercept|CheckPerm|NearBranch|
+            No16))) {
                /*
                 * These are copied unconditionally here, and checked unconditionally
                 * in x86_emulate_insn.
@@ -4596,6 +4598,9 @@ done_prefixes:
                                ctxt->op_bytes = 4;
                }
 
+               if ((ctxt->d & No16) && ctxt->op_bytes == 2)
+                       ctxt->op_bytes = 4;
+
                if (ctxt->d & Sse)
                        ctxt->op_bytes = 16;
                else if (ctxt->d & Mmx)
@@ -5061,11 +5066,6 @@ twobyte_insn:
                ctxt->dst.val = (ctxt->src.bytes == 1) ? (s8) ctxt->src.val :
                                                        (s16) ctxt->src.val;
                break;
-       case 0xc3:              /* movnti */
-               ctxt->dst.bytes = ctxt->op_bytes;
-               ctxt->dst.val = (ctxt->op_bytes == 8) ? (u64) ctxt->src.val :
-                                                       (u32) ctxt->src.val;
-               break;
        default:
                goto cannot_emulate;
        }