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KVM: x86 emulator: Make emulate_push() store the value directly
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PUSH emulation stores the value by calling writeback() after setting
the dst operand appropriately in emulate_push().

This writeback() using dst is not needed at all because we know the
target is the stack.  So this patch makes emulate_push() call, newly
introduced, segmented_write() directly.

By this, many inlined writeback()'s are removed.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
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Takuya Yoshikawa authored and Avi Kivity committed May 11, 2011
1 parent 575e7c1 commit 4179bb0
Showing 1 changed file with 34 additions and 53 deletions.
87 changes: 34 additions & 53 deletions arch/x86/kvm/emulate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1345,17 +1345,19 @@ static inline int writeback(struct x86_emulate_ctxt *ctxt,
return X86EMUL_CONTINUE;
}

static inline void emulate_push(struct x86_emulate_ctxt *ctxt,
struct x86_emulate_ops *ops)
static int emulate_push(struct x86_emulate_ctxt *ctxt,
struct x86_emulate_ops *ops)
{
struct decode_cache *c = &ctxt->decode;
struct segmented_address addr;

c->dst.type = OP_MEM;
c->dst.bytes = c->op_bytes;
c->dst.val = c->src.val;
register_address_increment(c, &c->regs[VCPU_REGS_RSP], -c->op_bytes);
c->dst.addr.mem.ea = register_address(c, c->regs[VCPU_REGS_RSP]);
c->dst.addr.mem.seg = VCPU_SREG_SS;
addr.ea = register_address(c, c->regs[VCPU_REGS_RSP]);
addr.seg = VCPU_SREG_SS;

/* Disable writeback. */
c->dst.type = OP_NONE;
return segmented_write(ctxt, addr, &c->src.val, c->op_bytes);
}

static int emulate_pop(struct x86_emulate_ctxt *ctxt,
Expand Down Expand Up @@ -1417,14 +1419,14 @@ static int emulate_popf(struct x86_emulate_ctxt *ctxt,
return rc;
}

static void emulate_push_sreg(struct x86_emulate_ctxt *ctxt,
struct x86_emulate_ops *ops, int seg)
static int emulate_push_sreg(struct x86_emulate_ctxt *ctxt,
struct x86_emulate_ops *ops, int seg)
{
struct decode_cache *c = &ctxt->decode;

c->src.val = ops->get_segment_selector(seg, ctxt->vcpu);

emulate_push(ctxt, ops);
return emulate_push(ctxt, ops);
}

static int emulate_pop_sreg(struct x86_emulate_ctxt *ctxt,
Expand Down Expand Up @@ -1454,18 +1456,13 @@ static int emulate_pusha(struct x86_emulate_ctxt *ctxt,
(reg == VCPU_REGS_RSP) ?
(c->src.val = old_esp) : (c->src.val = c->regs[reg]);

emulate_push(ctxt, ops);

rc = writeback(ctxt, ops);
rc = emulate_push(ctxt, ops);
if (rc != X86EMUL_CONTINUE)
return rc;

++reg;
}

/* Disable writeback. */
c->dst.type = OP_NONE;

return rc;
}

Expand Down Expand Up @@ -1503,27 +1500,22 @@ int emulate_int_real(struct x86_emulate_ctxt *ctxt,

/* TODO: Add limit checks */
c->src.val = ctxt->eflags;
emulate_push(ctxt, ops);
rc = writeback(ctxt, ops);
rc = emulate_push(ctxt, ops);
if (rc != X86EMUL_CONTINUE)
return rc;

ctxt->eflags &= ~(EFLG_IF | EFLG_TF | EFLG_AC);

c->src.val = ops->get_segment_selector(VCPU_SREG_CS, ctxt->vcpu);
emulate_push(ctxt, ops);
rc = writeback(ctxt, ops);
rc = emulate_push(ctxt, ops);
if (rc != X86EMUL_CONTINUE)
return rc;

c->src.val = c->eip;
emulate_push(ctxt, ops);
rc = writeback(ctxt, ops);
rc = emulate_push(ctxt, ops);
if (rc != X86EMUL_CONTINUE)
return rc;

c->dst.type = OP_NONE;

ops->get_idt(&dt, ctxt->vcpu);

eip_addr = dt.address + (irq << 2);
Expand Down Expand Up @@ -1713,6 +1705,7 @@ static inline int emulate_grp45(struct x86_emulate_ctxt *ctxt,
struct x86_emulate_ops *ops)
{
struct decode_cache *c = &ctxt->decode;
int rc = X86EMUL_CONTINUE;

switch (c->modrm_reg) {
case 0: /* inc */
Expand All @@ -1726,17 +1719,17 @@ static inline int emulate_grp45(struct x86_emulate_ctxt *ctxt,
old_eip = c->eip;
c->eip = c->src.val;
c->src.val = old_eip;
emulate_push(ctxt, ops);
rc = emulate_push(ctxt, ops);
break;
}
case 4: /* jmp abs */
c->eip = c->src.val;
break;
case 6: /* push */
emulate_push(ctxt, ops);
rc = emulate_push(ctxt, ops);
break;
}
return X86EMUL_CONTINUE;
return rc;
}

static inline int emulate_grp9(struct x86_emulate_ctxt *ctxt,
Expand Down Expand Up @@ -2380,7 +2373,7 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
c->op_bytes = c->ad_bytes = (next_tss_desc.type & 8) ? 4 : 2;
c->lock_prefix = 0;
c->src.val = (unsigned long) error_code;
emulate_push(ctxt, ops);
ret = emulate_push(ctxt, ops);
}

return ret;
Expand All @@ -2400,11 +2393,8 @@ int emulator_task_switch(struct x86_emulate_ctxt *ctxt,
rc = emulator_do_task_switch(ctxt, ops, tss_selector, reason,
has_error_code, error_code);

if (rc == X86EMUL_CONTINUE) {
rc = writeback(ctxt, ops);
if (rc == X86EMUL_CONTINUE)
ctxt->eip = c->eip;
}
if (rc == X86EMUL_CONTINUE)
ctxt->eip = c->eip;

return (rc == X86EMUL_UNHANDLEABLE) ? EMULATION_FAILED : EMULATION_OK;
}
Expand All @@ -2422,8 +2412,7 @@ static void string_addr_inc(struct x86_emulate_ctxt *ctxt, unsigned seg,

static int em_push(struct x86_emulate_ctxt *ctxt)
{
emulate_push(ctxt, ctxt->ops);
return X86EMUL_CONTINUE;
return emulate_push(ctxt, ctxt->ops);
}

static int em_das(struct x86_emulate_ctxt *ctxt)
Expand Down Expand Up @@ -2483,20 +2472,12 @@ static int em_call_far(struct x86_emulate_ctxt *ctxt)
memcpy(&c->eip, c->src.valptr, c->op_bytes);

c->src.val = old_cs;
emulate_push(ctxt, ctxt->ops);
rc = writeback(ctxt, ctxt->ops);
rc = emulate_push(ctxt, ctxt->ops);
if (rc != X86EMUL_CONTINUE)
return rc;

c->src.val = old_eip;
emulate_push(ctxt, ctxt->ops);
rc = writeback(ctxt, ctxt->ops);
if (rc != X86EMUL_CONTINUE)
return rc;

c->dst.type = OP_NONE;

return X86EMUL_CONTINUE;
return emulate_push(ctxt, ctxt->ops);
}

static int em_ret_near_imm(struct x86_emulate_ctxt *ctxt)
Expand Down Expand Up @@ -3625,7 +3606,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
emulate_2op_SrcV("add", c->src, c->dst, ctxt->eflags);
break;
case 0x06: /* push es */
emulate_push_sreg(ctxt, ops, VCPU_SREG_ES);
rc = emulate_push_sreg(ctxt, ops, VCPU_SREG_ES);
break;
case 0x07: /* pop es */
rc = emulate_pop_sreg(ctxt, ops, VCPU_SREG_ES);
Expand All @@ -3635,14 +3616,14 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
emulate_2op_SrcV("or", c->src, c->dst, ctxt->eflags);
break;
case 0x0e: /* push cs */
emulate_push_sreg(ctxt, ops, VCPU_SREG_CS);
rc = emulate_push_sreg(ctxt, ops, VCPU_SREG_CS);
break;
case 0x10 ... 0x15:
adc: /* adc */
emulate_2op_SrcV("adc", c->src, c->dst, ctxt->eflags);
break;
case 0x16: /* push ss */
emulate_push_sreg(ctxt, ops, VCPU_SREG_SS);
rc = emulate_push_sreg(ctxt, ops, VCPU_SREG_SS);
break;
case 0x17: /* pop ss */
rc = emulate_pop_sreg(ctxt, ops, VCPU_SREG_SS);
Expand All @@ -3652,7 +3633,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
emulate_2op_SrcV("sbb", c->src, c->dst, ctxt->eflags);
break;
case 0x1e: /* push ds */
emulate_push_sreg(ctxt, ops, VCPU_SREG_DS);
rc = emulate_push_sreg(ctxt, ops, VCPU_SREG_DS);
break;
case 0x1f: /* pop ds */
rc = emulate_pop_sreg(ctxt, ops, VCPU_SREG_DS);
Expand Down Expand Up @@ -3789,7 +3770,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
break;
case 0x9c: /* pushf */
c->src.val = (unsigned long) ctxt->eflags;
emulate_push(ctxt, ops);
rc = emulate_push(ctxt, ops);
break;
case 0x9d: /* popf */
c->dst.type = OP_REG;
Expand Down Expand Up @@ -3864,7 +3845,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
long int rel = c->src.val;
c->src.val = (unsigned long) c->eip;
jmp_rel(c, rel);
emulate_push(ctxt, ops);
rc = emulate_push(ctxt, ops);
break;
}
case 0xe9: /* jmp rel */
Expand Down Expand Up @@ -4157,7 +4138,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
c->dst.val = test_cc(c->b, ctxt->eflags);
break;
case 0xa0: /* push fs */
emulate_push_sreg(ctxt, ops, VCPU_SREG_FS);
rc = emulate_push_sreg(ctxt, ops, VCPU_SREG_FS);
break;
case 0xa1: /* pop fs */
rc = emulate_pop_sreg(ctxt, ops, VCPU_SREG_FS);
Expand All @@ -4174,7 +4155,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
emulate_2op_cl("shld", c->src2, c->src, c->dst, ctxt->eflags);
break;
case 0xa8: /* push gs */
emulate_push_sreg(ctxt, ops, VCPU_SREG_GS);
rc = emulate_push_sreg(ctxt, ops, VCPU_SREG_GS);
break;
case 0xa9: /* pop gs */
rc = emulate_pop_sreg(ctxt, ops, VCPU_SREG_GS);
Expand Down

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