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@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_emulate.h | 1 +
arch/x86/kvm/emulate.c | 13 +------------
arch/x86/kvm/x86.c | 7 +++++++
3 files changed, 9 insertions(+), 12 deletions(-)
diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index f751657..df53ba2 100644
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -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);
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 37b20c3..41c77a1 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -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 ? */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 69db0c8..2829e8f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3652,6 +3652,12 @@ 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)
{
@@ -3742,6 +3748,7 @@ 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,
--
1.6.5
--
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