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KVM: emulate: rework seg_override
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x86_decode_insn already sets a default for seg_override,
so remove it from the zeroed area. Also replace set/get functions
with direct access to the field.

Signed-off-by: Bandan Das <bsd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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@whitebrandy @bonzini
whitebrandy authored and bonzini committed Jul 11, 2014
1 parent c44b4c6 commit 573e80f
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Showing 2 changed files with 17 additions and 27 deletions.
3 changes: 1 addition & 2 deletions arch/x86/include/asm/kvm_emulate.h
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Original file line number Diff line number Diff line change
Expand Up @@ -295,12 +295,10 @@ struct x86_emulate_ctxt {
struct operand dst;
int (*execute)(struct x86_emulate_ctxt *ctxt);
int (*check_perm)(struct x86_emulate_ctxt *ctxt);
bool has_seg_override;
bool rip_relative;
u8 rex_prefix;
u8 lock_prefix;
u8 rep_prefix;
u8 seg_override;
/* bitmaps of registers in _regs[] that can be read */
u32 regs_valid;
/* bitmaps of registers in _regs[] that have been written */
Expand All @@ -311,6 +309,7 @@ struct x86_emulate_ctxt {
u8 modrm_reg;
u8 modrm_rm;
u8 modrm_seg;
u8 seg_override;
u64 d;
unsigned long _eip;
struct operand memop;
Expand Down
41 changes: 16 additions & 25 deletions arch/x86/kvm/emulate.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -514,12 +514,6 @@ static u32 desc_limit_scaled(struct desc_struct *desc)
return desc->g ? (limit << 12) | 0xfff : limit;
}

static void set_seg_override(struct x86_emulate_ctxt *ctxt, int seg)
{
ctxt->has_seg_override = true;
ctxt->seg_override = seg;
}

static unsigned long seg_base(struct x86_emulate_ctxt *ctxt, int seg)
{
if (ctxt->mode == X86EMUL_MODE_PROT64 && seg < VCPU_SREG_FS)
Expand All @@ -528,14 +522,6 @@ static unsigned long seg_base(struct x86_emulate_ctxt *ctxt, int seg)
return ctxt->ops->get_cached_segment_base(ctxt, seg);
}

static unsigned seg_override(struct x86_emulate_ctxt *ctxt)
{
if (!ctxt->has_seg_override)
return 0;

return ctxt->seg_override;
}

static int emulate_exception(struct x86_emulate_ctxt *ctxt, int vec,
u32 error, bool valid)
{
Expand Down Expand Up @@ -4169,7 +4155,7 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
op->bytes = (ctxt->d & ByteOp) ? 1 : ctxt->op_bytes;
op->addr.mem.ea =
register_address(ctxt, reg_read(ctxt, VCPU_REGS_RSI));
op->addr.mem.seg = seg_override(ctxt);
op->addr.mem.seg = ctxt->seg_override;
op->val = 0;
op->count = 1;
break;
Expand All @@ -4180,7 +4166,7 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
register_address(ctxt,
reg_read(ctxt, VCPU_REGS_RBX) +
(reg_read(ctxt, VCPU_REGS_RAX) & 0xff));
op->addr.mem.seg = seg_override(ctxt);
op->addr.mem.seg = ctxt->seg_override;
op->val = 0;
break;
case OpImmFAddr:
Expand Down Expand Up @@ -4227,6 +4213,7 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
int mode = ctxt->mode;
int def_op_bytes, def_ad_bytes, goffset, simd_prefix;
bool op_prefix = false;
bool has_seg_override = false;
struct opcode opcode;

ctxt->memop.type = OP_NONE;
Expand Down Expand Up @@ -4280,11 +4267,13 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
case 0x2e: /* CS override */
case 0x36: /* SS override */
case 0x3e: /* DS override */
set_seg_override(ctxt, (ctxt->b >> 3) & 3);
has_seg_override = true;
ctxt->seg_override = (ctxt->b >> 3) & 3;
break;
case 0x64: /* FS override */
case 0x65: /* GS override */
set_seg_override(ctxt, ctxt->b & 7);
has_seg_override = true;
ctxt->seg_override = ctxt->b & 7;
break;
case 0x40 ... 0x4f: /* REX */
if (mode != X86EMUL_MODE_PROT64)
Expand Down Expand Up @@ -4422,17 +4411,19 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
/* ModRM and SIB bytes. */
if (ctxt->d & ModRM) {
rc = decode_modrm(ctxt, &ctxt->memop);
if (!ctxt->has_seg_override)
set_seg_override(ctxt, ctxt->modrm_seg);
if (!has_seg_override) {
has_seg_override = true;
ctxt->seg_override = ctxt->modrm_seg;
}
} else if (ctxt->d & MemAbs)
rc = decode_abs(ctxt, &ctxt->memop);
if (rc != X86EMUL_CONTINUE)
goto done;

if (!ctxt->has_seg_override)
set_seg_override(ctxt, VCPU_SREG_DS);
if (!has_seg_override)
ctxt->seg_override = VCPU_SREG_DS;

ctxt->memop.addr.mem.seg = seg_override(ctxt);
ctxt->memop.addr.mem.seg = ctxt->seg_override;

if (ctxt->memop.type == OP_MEM && ctxt->ad_bytes != 8)
ctxt->memop.addr.mem.ea = (u32)ctxt->memop.addr.mem.ea;
Expand Down Expand Up @@ -4534,8 +4525,8 @@ static int fastop(struct x86_emulate_ctxt *ctxt, void (*fop)(struct fastop *))

void init_decode_cache(struct x86_emulate_ctxt *ctxt)
{
memset(&ctxt->has_seg_override, 0,
(void *)&ctxt->modrm - (void *)&ctxt->has_seg_override);
memset(&ctxt->rip_relative, 0,
(void *)&ctxt->modrm - (void *)&ctxt->rip_relative);

ctxt->io_read.pos = 0;
ctxt->io_read.end = 0;
Expand Down

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