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>

diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c
index 76b813b6365c449a59c7329a456e95c7351e3f87..6161e3f665856cc6b90ef7d5a01baada0f5f9ad2 100644 (file)
--- 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:

diff --git a/drivers/kvm/x86_emulate.h b/drivers/kvm/x86_emulate.h
index 28acad416bcad0b4cfbb001f67a444b959bcfa4f..f03b1287700a6e9877e0cc394713721f82cfec2e 100644 (file)
--- a/drivers/kvm/x86_emulate.h
+++ b/drivers/kvm/x86_emulate.h
@@ -114,7 +114,7 @@ struct x86_emulate_ops {
 
 /* Type, address-of, and value of an instruction's operand. */
 struct operand {
-       enum { OP_REG, OP_MEM, OP_IMM } type;
+       enum { OP_REG, OP_MEM, OP_IMM, OP_NONE } type;
        unsigned int bytes;
        unsigned long val, orig_val, *ptr;
 };