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KVM: x86 emulator: consolidate segment accessors
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Instead of separate accessors for the segment selector and cached descriptor,
use one accessor for both.  This simplifies the code somewhat.

Signed-off-by: Avi Kivity <avi@redhat.com>
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@avikivity
avikivity committed May 22, 2011
1 parent 0a434bb commit 1aa3661
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Showing 3 changed files with 83 additions and 93 deletions.
13 changes: 4 additions & 9 deletions arch/x86/include/asm/kvm_emulate.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -164,15 +164,10 @@ struct x86_emulate_ops {
int size, unsigned short port, const void *val,
unsigned int count);

bool (*get_cached_descriptor)(struct x86_emulate_ctxt *ctxt,
struct desc_struct *desc, u32 *base3,
int seg);
void (*set_cached_descriptor)(struct x86_emulate_ctxt *ctxt,
struct desc_struct *desc, u32 base3,
int seg);
u16 (*get_segment_selector)(struct x86_emulate_ctxt *ctxt, int seg);
void (*set_segment_selector)(struct x86_emulate_ctxt *ctxt,
u16 sel, int seg);
bool (*get_segment)(struct x86_emulate_ctxt *ctxt, u16 *selector,
struct desc_struct *desc, u32 *base3, int seg);
void (*set_segment)(struct x86_emulate_ctxt *ctxt, u16 selector,
struct desc_struct *desc, u32 base3, int seg);
unsigned long (*get_cached_segment_base)(struct x86_emulate_ctxt *ctxt,
int seg);
void (*get_gdt)(struct x86_emulate_ctxt *ctxt, struct desc_ptr *dt);
Expand Down
122 changes: 69 additions & 53 deletions arch/x86/kvm/emulate.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -553,6 +553,26 @@ static int emulate_nm(struct x86_emulate_ctxt *ctxt)
return emulate_exception(ctxt, NM_VECTOR, 0, false);
}

static u16 get_segment_selector(struct x86_emulate_ctxt *ctxt, unsigned seg)
{
u16 selector;
struct desc_struct desc;

ctxt->ops->get_segment(ctxt, &selector, &desc, NULL, seg);
return selector;
}

static void set_segment_selector(struct x86_emulate_ctxt *ctxt, u16 selector,
unsigned seg)
{
u16 dummy;
u32 base3;
struct desc_struct desc;

ctxt->ops->get_segment(ctxt, &dummy, &desc, &base3, seg);
ctxt->ops->set_segment(ctxt, selector, &desc, base3, seg);
}

static int __linearize(struct x86_emulate_ctxt *ctxt,
struct segmented_address addr,
unsigned size, bool write, bool fetch,
Expand All @@ -563,6 +583,7 @@ static int __linearize(struct x86_emulate_ctxt *ctxt,
bool usable;
ulong la;
u32 lim;
u16 sel;
unsigned cpl, rpl;

la = seg_base(ctxt, ctxt->ops, addr.seg) + addr.ea;
Expand All @@ -574,8 +595,8 @@ static int __linearize(struct x86_emulate_ctxt *ctxt,
return emulate_gp(ctxt, 0);
break;
default:
usable = ctxt->ops->get_cached_descriptor(ctxt, &desc, NULL,
addr.seg);
usable = ctxt->ops->get_segment(ctxt, &sel, &desc, NULL,
addr.seg);
if (!usable)
goto bad;
/* code segment or read-only data segment */
Expand All @@ -598,7 +619,7 @@ static int __linearize(struct x86_emulate_ctxt *ctxt,
goto bad;
}
cpl = ctxt->ops->cpl(ctxt);
rpl = ctxt->ops->get_segment_selector(ctxt, addr.seg) & 3;
rpl = sel & 3;
cpl = max(cpl, rpl);
if (!(desc.type & 8)) {
/* data segment */
Expand Down Expand Up @@ -1142,9 +1163,10 @@ static void get_descriptor_table_ptr(struct x86_emulate_ctxt *ctxt,
{
if (selector & 1 << 2) {
struct desc_struct desc;
u16 sel;

memset (dt, 0, sizeof *dt);
if (!ops->get_cached_descriptor(ctxt, &desc, NULL,
VCPU_SREG_LDTR))
if (!ops->get_segment(ctxt, &sel, &desc, NULL, VCPU_SREG_LDTR))
return;

dt->size = desc_limit_scaled(&desc); /* what if limit > 65535? */
Expand Down Expand Up @@ -1305,8 +1327,7 @@ static int load_segment_descriptor(struct x86_emulate_ctxt *ctxt,
return ret;
}
load:
ops->set_segment_selector(ctxt, selector, seg);
ops->set_cached_descriptor(ctxt, &seg_desc, 0, seg);
ops->set_segment(ctxt, selector, &seg_desc, 0, seg);
return X86EMUL_CONTINUE;
exception:
emulate_exception(ctxt, err_vec, err_code, true);
Expand Down Expand Up @@ -1464,7 +1485,7 @@ static int emulate_push_sreg(struct x86_emulate_ctxt *ctxt,
{
struct decode_cache *c = &ctxt->decode;

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

return em_push(ctxt);
}
Expand Down Expand Up @@ -1552,7 +1573,7 @@ int emulate_int_real(struct x86_emulate_ctxt *ctxt,

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

c->src.val = ops->get_segment_selector(ctxt, VCPU_SREG_CS);
c->src.val = get_segment_selector(ctxt, VCPU_SREG_CS);
rc = em_push(ctxt);
if (rc != X86EMUL_CONTINUE)
return rc;
Expand Down Expand Up @@ -1838,8 +1859,10 @@ setup_syscalls_segments(struct x86_emulate_ctxt *ctxt,
struct x86_emulate_ops *ops, struct desc_struct *cs,
struct desc_struct *ss)
{
u16 selector;

memset(cs, 0, sizeof(struct desc_struct));
ops->get_cached_descriptor(ctxt, cs, NULL, VCPU_SREG_CS);
ops->get_segment(ctxt, &selector, cs, NULL, VCPU_SREG_CS);
memset(ss, 0, sizeof(struct desc_struct));

cs->l = 0; /* will be adjusted later */
Expand Down Expand Up @@ -1888,10 +1911,8 @@ emulate_syscall(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
cs.d = 0;
cs.l = 1;
}
ops->set_cached_descriptor(ctxt, &cs, 0, VCPU_SREG_CS);
ops->set_segment_selector(ctxt, cs_sel, VCPU_SREG_CS);
ops->set_cached_descriptor(ctxt, &ss, 0, VCPU_SREG_SS);
ops->set_segment_selector(ctxt, ss_sel, VCPU_SREG_SS);
ops->set_segment(ctxt, cs_sel, &cs, 0, VCPU_SREG_CS);
ops->set_segment(ctxt, ss_sel, &ss, 0, VCPU_SREG_SS);

c->regs[VCPU_REGS_RCX] = c->eip;
if (efer & EFER_LMA) {
Expand Down Expand Up @@ -1961,10 +1982,8 @@ emulate_sysenter(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
cs.l = 1;
}

ops->set_cached_descriptor(ctxt, &cs, 0, VCPU_SREG_CS);
ops->set_segment_selector(ctxt, cs_sel, VCPU_SREG_CS);
ops->set_cached_descriptor(ctxt, &ss, 0, VCPU_SREG_SS);
ops->set_segment_selector(ctxt, ss_sel, VCPU_SREG_SS);
ops->set_segment(ctxt, cs_sel, &cs, 0, VCPU_SREG_CS);
ops->set_segment(ctxt, ss_sel, &ss, 0, VCPU_SREG_SS);

ops->get_msr(ctxt, MSR_IA32_SYSENTER_EIP, &msr_data);
c->eip = msr_data;
Expand Down Expand Up @@ -2018,10 +2037,8 @@ emulate_sysexit(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
cs_sel |= SELECTOR_RPL_MASK;
ss_sel |= SELECTOR_RPL_MASK;

ops->set_cached_descriptor(ctxt, &cs, 0, VCPU_SREG_CS);
ops->set_segment_selector(ctxt, cs_sel, VCPU_SREG_CS);
ops->set_cached_descriptor(ctxt, &ss, 0, VCPU_SREG_SS);
ops->set_segment_selector(ctxt, ss_sel, VCPU_SREG_SS);
ops->set_segment(ctxt, cs_sel, &cs, 0, VCPU_SREG_CS);
ops->set_segment(ctxt, ss_sel, &ss, 0, VCPU_SREG_SS);

c->eip = c->regs[VCPU_REGS_RDX];
c->regs[VCPU_REGS_RSP] = c->regs[VCPU_REGS_RCX];
Expand All @@ -2048,11 +2065,11 @@ static bool emulator_io_port_access_allowed(struct x86_emulate_ctxt *ctxt,
struct desc_struct tr_seg;
u32 base3;
int r;
u16 io_bitmap_ptr, perm, bit_idx = port & 0x7;
u16 tr, io_bitmap_ptr, perm, bit_idx = port & 0x7;
unsigned mask = (1 << len) - 1;
unsigned long base;

ops->get_cached_descriptor(ctxt, &tr_seg, &base3, VCPU_SREG_TR);
ops->get_segment(ctxt, &tr, &tr_seg, &base3, VCPU_SREG_TR);
if (!tr_seg.p)
return false;
if (desc_limit_scaled(&tr_seg) < 103)
Expand Down Expand Up @@ -2107,11 +2124,11 @@ static void save_state_to_tss16(struct x86_emulate_ctxt *ctxt,
tss->si = c->regs[VCPU_REGS_RSI];
tss->di = c->regs[VCPU_REGS_RDI];

tss->es = ops->get_segment_selector(ctxt, VCPU_SREG_ES);
tss->cs = ops->get_segment_selector(ctxt, VCPU_SREG_CS);
tss->ss = ops->get_segment_selector(ctxt, VCPU_SREG_SS);
tss->ds = ops->get_segment_selector(ctxt, VCPU_SREG_DS);
tss->ldt = ops->get_segment_selector(ctxt, VCPU_SREG_LDTR);
tss->es = get_segment_selector(ctxt, VCPU_SREG_ES);
tss->cs = get_segment_selector(ctxt, VCPU_SREG_CS);
tss->ss = get_segment_selector(ctxt, VCPU_SREG_SS);
tss->ds = get_segment_selector(ctxt, VCPU_SREG_DS);
tss->ldt = get_segment_selector(ctxt, VCPU_SREG_LDTR);
}

static int load_state_from_tss16(struct x86_emulate_ctxt *ctxt,
Expand All @@ -2136,11 +2153,11 @@ static int load_state_from_tss16(struct x86_emulate_ctxt *ctxt,
* SDM says that segment selectors are loaded before segment
* descriptors
*/
ops->set_segment_selector(ctxt, tss->ldt, VCPU_SREG_LDTR);
ops->set_segment_selector(ctxt, tss->es, VCPU_SREG_ES);
ops->set_segment_selector(ctxt, tss->cs, VCPU_SREG_CS);
ops->set_segment_selector(ctxt, tss->ss, VCPU_SREG_SS);
ops->set_segment_selector(ctxt, tss->ds, VCPU_SREG_DS);
set_segment_selector(ctxt, tss->ldt, VCPU_SREG_LDTR);
set_segment_selector(ctxt, tss->es, VCPU_SREG_ES);
set_segment_selector(ctxt, tss->cs, VCPU_SREG_CS);
set_segment_selector(ctxt, tss->ss, VCPU_SREG_SS);
set_segment_selector(ctxt, tss->ds, VCPU_SREG_DS);

/*
* Now load segment descriptors. If fault happenes at this stage
Expand Down Expand Up @@ -2227,13 +2244,13 @@ static void save_state_to_tss32(struct x86_emulate_ctxt *ctxt,
tss->esi = c->regs[VCPU_REGS_RSI];
tss->edi = c->regs[VCPU_REGS_RDI];

tss->es = ops->get_segment_selector(ctxt, VCPU_SREG_ES);
tss->cs = ops->get_segment_selector(ctxt, VCPU_SREG_CS);
tss->ss = ops->get_segment_selector(ctxt, VCPU_SREG_SS);
tss->ds = ops->get_segment_selector(ctxt, VCPU_SREG_DS);
tss->fs = ops->get_segment_selector(ctxt, VCPU_SREG_FS);
tss->gs = ops->get_segment_selector(ctxt, VCPU_SREG_GS);
tss->ldt_selector = ops->get_segment_selector(ctxt, VCPU_SREG_LDTR);
tss->es = get_segment_selector(ctxt, VCPU_SREG_ES);
tss->cs = get_segment_selector(ctxt, VCPU_SREG_CS);
tss->ss = get_segment_selector(ctxt, VCPU_SREG_SS);
tss->ds = get_segment_selector(ctxt, VCPU_SREG_DS);
tss->fs = get_segment_selector(ctxt, VCPU_SREG_FS);
tss->gs = get_segment_selector(ctxt, VCPU_SREG_GS);
tss->ldt_selector = get_segment_selector(ctxt, VCPU_SREG_LDTR);
}

static int load_state_from_tss32(struct x86_emulate_ctxt *ctxt,
Expand All @@ -2260,13 +2277,13 @@ static int load_state_from_tss32(struct x86_emulate_ctxt *ctxt,
* SDM says that segment selectors are loaded before segment
* descriptors
*/
ops->set_segment_selector(ctxt, tss->ldt_selector, VCPU_SREG_LDTR);
ops->set_segment_selector(ctxt, tss->es, VCPU_SREG_ES);
ops->set_segment_selector(ctxt, tss->cs, VCPU_SREG_CS);
ops->set_segment_selector(ctxt, tss->ss, VCPU_SREG_SS);
ops->set_segment_selector(ctxt, tss->ds, VCPU_SREG_DS);
ops->set_segment_selector(ctxt, tss->fs, VCPU_SREG_FS);
ops->set_segment_selector(ctxt, tss->gs, VCPU_SREG_GS);
set_segment_selector(ctxt, tss->ldt_selector, VCPU_SREG_LDTR);
set_segment_selector(ctxt, tss->es, VCPU_SREG_ES);
set_segment_selector(ctxt, tss->cs, VCPU_SREG_CS);
set_segment_selector(ctxt, tss->ss, VCPU_SREG_SS);
set_segment_selector(ctxt, tss->ds, VCPU_SREG_DS);
set_segment_selector(ctxt, tss->fs, VCPU_SREG_FS);
set_segment_selector(ctxt, tss->gs, VCPU_SREG_GS);

/*
* Now load segment descriptors. If fault happenes at this stage
Expand Down Expand Up @@ -2348,7 +2365,7 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
{
struct desc_struct curr_tss_desc, next_tss_desc;
int ret;
u16 old_tss_sel = ops->get_segment_selector(ctxt, VCPU_SREG_TR);
u16 old_tss_sel = get_segment_selector(ctxt, VCPU_SREG_TR);
ulong old_tss_base =
ops->get_cached_segment_base(ctxt, VCPU_SREG_TR);
u32 desc_limit;
Expand Down Expand Up @@ -2411,8 +2428,7 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
}

ops->set_cr(ctxt, 0, ops->get_cr(ctxt, 0) | X86_CR0_TS);
ops->set_cached_descriptor(ctxt, &next_tss_desc, 0, VCPU_SREG_TR);
ops->set_segment_selector(ctxt, tss_selector, VCPU_SREG_TR);
ops->set_segment(ctxt, tss_selector, &next_tss_desc, 0, VCPU_SREG_TR);

if (has_error_code) {
struct decode_cache *c = &ctxt->decode;
Expand Down Expand Up @@ -2503,7 +2519,7 @@ static int em_call_far(struct x86_emulate_ctxt *ctxt)
ulong old_eip;
int rc;

old_cs = ctxt->ops->get_segment_selector(ctxt, VCPU_SREG_CS);
old_cs = get_segment_selector(ctxt, VCPU_SREG_CS);
old_eip = c->eip;

memcpy(&sel, c->src.valptr + c->op_bytes, 2);
Expand Down Expand Up @@ -3881,7 +3897,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
rc = emulate_ud(ctxt);
goto done;
}
c->dst.val = ops->get_segment_selector(ctxt, c->modrm_reg);
c->dst.val = get_segment_selector(ctxt, c->modrm_reg);
break;
case 0x8d: /* lea r16/r32, m */
c->dst.val = c->src.addr.mem.ea;
Expand Down
41 changes: 10 additions & 31 deletions arch/x86/kvm/x86.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4304,13 +4304,14 @@ static unsigned long emulator_get_cached_segment_base(
return get_segment_base(emul_to_vcpu(ctxt), seg);
}

static bool emulator_get_cached_descriptor(struct x86_emulate_ctxt *ctxt,
struct desc_struct *desc, u32 *base3,
int seg)
static bool emulator_get_segment(struct x86_emulate_ctxt *ctxt, u16 *selector,
struct desc_struct *desc, u32 *base3,
int seg)
{
struct kvm_segment var;

kvm_get_segment(emul_to_vcpu(ctxt), &var, seg);
*selector = var.selector;

if (var.unusable)
return false;
Expand All @@ -4335,16 +4336,14 @@ static bool emulator_get_cached_descriptor(struct x86_emulate_ctxt *ctxt,
return true;
}

static void emulator_set_cached_descriptor(struct x86_emulate_ctxt *ctxt,
struct desc_struct *desc, u32 base3,
int seg)
static void emulator_set_segment(struct x86_emulate_ctxt *ctxt, u16 selector,
struct desc_struct *desc, u32 base3,
int seg)
{
struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
struct kvm_segment var;

/* needed to preserve selector */
kvm_get_segment(vcpu, &var, seg);

var.selector = selector;
var.base = get_desc_base(desc);
#ifdef CONFIG_X86_64
var.base |= ((u64)base3) << 32;
Expand All @@ -4368,24 +4367,6 @@ static void emulator_set_cached_descriptor(struct x86_emulate_ctxt *ctxt,
return;
}

static u16 emulator_get_segment_selector(struct x86_emulate_ctxt *ctxt, int seg)
{
struct kvm_segment kvm_seg;

kvm_get_segment(emul_to_vcpu(ctxt), &kvm_seg, seg);
return kvm_seg.selector;
}

static void emulator_set_segment_selector(struct x86_emulate_ctxt *ctxt,
u16 sel, int seg)
{
struct kvm_segment kvm_seg;

kvm_get_segment(emul_to_vcpu(ctxt), &kvm_seg, seg);
kvm_seg.selector = sel;
kvm_set_segment(emul_to_vcpu(ctxt), &kvm_seg, seg);
}

static int emulator_get_msr(struct x86_emulate_ctxt *ctxt,
u32 msr_index, u64 *pdata)
{
Expand Down Expand Up @@ -4436,10 +4417,8 @@ static struct x86_emulate_ops emulate_ops = {
.invlpg = emulator_invlpg,
.pio_in_emulated = emulator_pio_in_emulated,
.pio_out_emulated = emulator_pio_out_emulated,
.get_cached_descriptor = emulator_get_cached_descriptor,
.set_cached_descriptor = emulator_set_cached_descriptor,
.get_segment_selector = emulator_get_segment_selector,
.set_segment_selector = emulator_set_segment_selector,
.get_segment = emulator_get_segment,
.set_segment = emulator_set_segment,
.get_cached_segment_base = emulator_get_cached_segment_base,
.get_gdt = emulator_get_gdt,
.get_idt = emulator_get_idt,
Expand Down

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