KVM: x86 emulator: Remove no_wb, use dst.type = OP_NONE instead

Remove no_wb, use dst.type = OP_NONE instead, idea stollen from xen-3.1

Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 24 insertions, 52 deletions

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 76b813b6365c..6161e3f66585 100644
--- a/drivers/kvm/x86_emulate.c
+++ b/drivers/kvm/x86_emulate.c
@@ -1016,8 +1016,7 @@ done:
 }
 
 static inline int emulate_grp45(struct x86_emulate_ctxt *ctxt,
-                               struct x86_emulate_ops *ops,
-                               int *no_wb)
+                               struct x86_emulate_ops *ops)
 {
         struct decode_cache *c = &ctxt->decode;
         int rc;
@@ -1055,7 +1054,7 @@ static inline int emulate_grp45(struct x86_emulate_ctxt *ctxt,
                                     c->dst.bytes, ctxt->vcpu);
                 if (rc != 0)
                         return rc;
-                *no_wb = 1;
+                c->dst.type = OP_NONE;
                 break;
         default:
                 DPRINTF("Cannot emulate %02x\n", c->b);
@@ -1137,6 +1136,10 @@ static inline int writeback(struct x86_emulate_ctxt *ctxt,
                                         ctxt->vcpu);
                 if (rc != 0)
                         return rc;
+                break;
+        case OP_NONE:
+                /* no writeback */
+                break;
         default:
                 break;
         }
@@ -1147,7 +1150,6 @@ int
 x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
 {
         unsigned long cr2 = ctxt->cr2;
-        int no_wb = 0;
         u64 msr_data;
         unsigned long saved_eip = 0;
         struct decode_cache *c = &ctxt->decode;
@@ -1344,18 +1346,16 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
                         goto done;
                 break;
         case 0xfe ... 0xff:     /* Grp4/Grp5 */
-                rc = emulate_grp45(ctxt, ops, &no_wb);
+                rc = emulate_grp45(ctxt, ops);
                 if (rc != 0)
                         goto done;
                 break;
         }
 
 writeback:
-        if (!no_wb) {
-                rc = writeback(ctxt, ops);
-                if (rc != 0)
-                        goto done;
-        }
+        rc = writeback(ctxt, ops);
+        if (rc != 0)
+                goto done;
 
         /* Commit shadow register state. */
         memcpy(ctxt->vcpu->regs, c->regs, sizeof c->regs);
@@ -1395,7 +1395,7 @@ special_insn:
 
                 register_address_increment(c->regs[VCPU_REGS_RSP],
                                            c->op_bytes);
-                no_wb = 1; /* Disable writeback. */
+                c->dst.type = OP_NONE;  /* Disable writeback. */
                 break;
         case 0x6a: /* push imm8 */
                 c->src.val = 0L;
@@ -1538,7 +1538,7 @@ special_insn:
         case 0xe9: /* jmp rel */
         case 0xeb: /* jmp rel short */
                 JMP_REL(c->src.val);
-                no_wb = 1; /* Disable writeback. */
+                c->dst.type = OP_NONE; /* Disable writeback. */
                 break;
 
 
@@ -1548,8 +1548,6 @@ special_insn:
 twobyte_insn:
         switch (c->b) {
         case 0x01: /* lgdt, lidt, lmsw */
-                /* Disable writeback. */
-                no_wb = 1;
                 switch (c->modrm_reg) {
                         u16 size;
                         unsigned long address;
@@ -1604,56 +1602,30 @@ twobyte_insn:
                 default:
                         goto cannot_emulate;
                 }
+                /* Disable writeback. */
+                c->dst.type = OP_NONE;
                 break;
         case 0x21: /* mov from dr to reg */
-                no_wb = 1;
                 if (c->modrm_mod != 3)
                         goto cannot_emulate;
                 rc = emulator_get_dr(ctxt, c->modrm_reg, &c->regs[c->modrm_rm]);
+                if (rc)
+                        goto cannot_emulate;
+                c->dst.type = OP_NONE;  /* no writeback */
                 break;
         case 0x23: /* mov from reg to dr */
-                no_wb = 1;
                 if (c->modrm_mod != 3)
                         goto cannot_emulate;
                 rc = emulator_set_dr(ctxt, c->modrm_reg,
                                      c->regs[c->modrm_rm]);
+                if (rc)
+                        goto cannot_emulate;
+                c->dst.type = OP_NONE;  /* no writeback */
                 break;
         case 0x40 ... 0x4f:     /* cmov */
                 c->dst.val = c->dst.orig_val = c->src.val;
-                no_wb = 1;
-                /*
-                 * First, assume we're decoding an even cmov opcode
-                 * (lsb == 0).
-                 */
-                switch ((c->b & 15) >> 1) {
-                case 0: /* cmovo */
-                        no_wb = (ctxt->eflags & EFLG_OF) ? 0 : 1;
-                        break;
-                case 1: /* cmovb/cmovc/cmovnae */
-                        no_wb = (ctxt->eflags & EFLG_CF) ? 0 : 1;
-                        break;
-                case 2: /* cmovz/cmove */
-                        no_wb = (ctxt->eflags & EFLG_ZF) ? 0 : 1;
-                        break;
-                case 3: /* cmovbe/cmovna */
-                        no_wb = (ctxt->eflags & (EFLG_CF | EFLG_ZF)) ? 0 : 1;
-                        break;
-                case 4: /* cmovs */
-                        no_wb = (ctxt->eflags & EFLG_SF) ? 0 : 1;
-                        break;
-                case 5: /* cmovp/cmovpe */
-                        no_wb = (ctxt->eflags & EFLG_PF) ? 0 : 1;
-                        break;
-                case 7: /* cmovle/cmovng */
-                        no_wb = (ctxt->eflags & EFLG_ZF) ? 0 : 1;
-                        /* fall through */
-                case 6: /* cmovl/cmovnge */
-                        no_wb &= (!(ctxt->eflags & EFLG_SF) !=
-                              !(ctxt->eflags & EFLG_OF)) ? 0 : 1;
-                        break;
-                }
-                /* Odd cmov opcodes (lsb == 1) have inverted sense. */
-                no_wb ^= c->b & 1;
+                if (!test_cc(c->b, ctxt->eflags))
+                        c->dst.type = OP_NONE; /* no writeback */
                 break;
         case 0xa3:
               bt:               /* bt */
@@ -1727,8 +1699,6 @@ twobyte_insn:
         goto writeback;
 
 twobyte_special_insn:
-        /* Disable writeback. */
-        no_wb = 1;
         switch (c->b) {
         case 0x06:
                 emulate_clts(ctxt->vcpu);
@@ -1802,6 +1772,8 @@ twobyte_special_insn:
                         goto done;
                 break;
         }
+        /* Disable writeback. */
+        c->dst.type = OP_NONE;
         goto writeback;
 
 cannot_emulate: