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KVM: x86 emulator: add get_cached_segment_base() callback to x86_emulate_ops

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On VMX it is expensive to call get_cached_descriptor() just to get segment
base since multiple vmcs_reads are done instead of only one. Introduce
new call back get_cached_segment_base() for efficiency.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Gleb Natapov 2010-04-28 19:15:29 +03:00 committed by Avi Kivity
parent 3fb1b5dbd3
commit 5951c44237
3 changed files with 9 additions and 12 deletions
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1
arch/x86/include/asm/kvm_emulate.h
View File

@ -132,6 +132,7 @@ struct x86_emulate_ops {
int seg, struct kvm_vcpu *vcpu);
u16 (*get_segment_selector)(int seg, struct kvm_vcpu *vcpu);
void (*set_segment_selector)(u16 sel, int seg, struct kvm_vcpu *vcpu);
unsigned long (*get_cached_segment_base)(int seg, struct kvm_vcpu *vcpu);
void (*get_gdt)(struct desc_ptr *dt, struct kvm_vcpu *vcpu);
ulong (*get_cr)(int cr, struct kvm_vcpu *vcpu);
void (*set_cr)(int cr, ulong val, struct kvm_vcpu *vcpu);

13
arch/x86/kvm/emulate.c
View File

@ -2097,17 +2097,6 @@ static bool emulator_io_permited(struct x86_emulate_ctxt *ctxt,
return true;
}
static u32 get_cached_descriptor_base(struct x86_emulate_ctxt *ctxt,
struct x86_emulate_ops *ops,
int seg)
{
struct desc_struct desc;
if (ops->get_cached_descriptor(&desc, seg, ctxt->vcpu))
return get_desc_base(&desc);
else
return ~0;
}
static void save_state_to_tss16(struct x86_emulate_ctxt *ctxt,
struct x86_emulate_ops *ops,
struct tss_segment_16 *tss)
@ -2383,7 +2372,7 @@ static int emulator_do_task_switch(struct x86_emulate_ctxt *ctxt,
int ret;
u16 old_tss_sel = ops->get_segment_selector(VCPU_SREG_TR, ctxt->vcpu);
ulong old_tss_base =
get_cached_descriptor_base(ctxt, ops, VCPU_SREG_TR);
ops->get_cached_segment_base(VCPU_SREG_TR, ctxt->vcpu);
u32 desc_limit;
/* FIXME: old_tss_base == ~0 ? */

7
arch/x86/kvm/x86.c
View File

@ -3714,6 +3714,12 @@ static void emulator_get_gdt(struct desc_ptr *dt, struct kvm_vcpu *vcpu)
kvm_x86_ops->get_gdt(vcpu, dt);
}
static unsigned long emulator_get_cached_segment_base(int seg,
struct kvm_vcpu *vcpu)
{
return get_segment_base(vcpu, seg);
}
static bool emulator_get_cached_descriptor(struct desc_struct *desc, int seg,
struct kvm_vcpu *vcpu)
{
@ -3804,6 +3810,7 @@ static struct x86_emulate_ops emulate_ops = {
.set_cached_descriptor = emulator_set_cached_descriptor,
.get_segment_selector = emulator_get_segment_selector,
.set_segment_selector = emulator_set_segment_selector,
.get_cached_segment_base = emulator_get_cached_segment_base,
.get_gdt = emulator_get_gdt,
.get_cr = emulator_get_cr,
.set_cr = emulator_set_cr,