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KVM: x86 emulator: Remove no_wb, use dst.type = OP_NONE instead
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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>
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Laurent Vivier authored and Avi Kivity committed Jan 30, 2008
1 parent 05f086f commit a01af5e
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Showing 2 changed files with 25 additions and 53 deletions.
76 changes: 24 additions & 52 deletions drivers/kvm/x86_emulate.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1016,8 +1016,7 @@ static inline int emulate_grp3(struct x86_emulate_ctxt *ctxt,
}

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;
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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;
}
Expand All @@ -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;
Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -1395,7 +1395,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)

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;
Expand Down Expand Up @@ -1538,7 +1538,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
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;


Expand All @@ -1548,8 +1548,6 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
twobyte_insn:
switch (c->b) {
case 0x01: /* lgdt, lidt, lmsw */
/* Disable writeback. */
no_wb = 1;
switch (c->modrm_reg) {
u16 size;
unsigned long address;
Expand Down Expand Up @@ -1604,56 +1602,30 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
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 */
Expand Down Expand Up @@ -1727,8 +1699,6 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
goto writeback;

twobyte_special_insn:
/* Disable writeback. */
no_wb = 1;
switch (c->b) {
case 0x06:
emulate_clts(ctxt->vcpu);
Expand Down Expand Up @@ -1802,6 +1772,8 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
goto done;
break;
}
/* Disable writeback. */
c->dst.type = OP_NONE;
goto writeback;

cannot_emulate:
Expand Down
2 changes: 1 addition & 1 deletion drivers/kvm/x86_emulate.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
};
Expand Down

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