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Commit 5951c442 authored by Gleb Natapov's avatar Gleb Natapov Committed by Avi Kivity
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KVM: x86 emulator: add get_cached_segment_base() callback to x86_emulate_ops 



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: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 3fb1b5db

arch/x86/include/asm/kvm_emulate.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

arch/x86/kvm/emulate.c

+1 −12
Original line number Diff line number Diff line
@@ -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 ? */

arch/x86/kvm/x86.c

+7 −0
Original line number Diff line number Diff line
@@ -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,