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Subject[RFC PATCH v2 5/6] KVM: emulate: rework seg_override
Date
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>
---
arch/x86/include/asm/kvm_emulate.h | 3 +--
arch/x86/kvm/emulate.c | 41 +++++++++++++++-----------------------
2 files changed, 17 insertions(+), 27 deletions(-)

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index d2ec45d..08a7696 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -322,12 +322,10 @@ 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 */
@@ -338,6 +336,7 @@ struct x86_emulate_ctxt {
u8 modrm_reg;
u8 modrm_rm;
u8 modrm_seg;
+ u8 seg_override;
u64 d;
unsigned long _eip;
struct operand memop;
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 5517dd2..b8affac 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -512,12 +512,6 @@ 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)
@@ -526,14 +520,6 @@ 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)
{
@@ -4192,7 +4178,7 @@ 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;
@@ -4203,7 +4189,7 @@ 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:
@@ -4250,6 +4236,7 @@ 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;
@@ -4303,11 +4290,13 @@ 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)
@@ -4438,17 +4427,19 @@ done_prefixes:
/* 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;
@@ -4550,8 +4541,8 @@ 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;
--
1.8.3.1


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