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Commit 7cf30855 authored by Sheng Yang's avatar Sheng Yang Committed by Avi Kivity
Browse files

KVM: x86: Use unlazy_fpu() for host FPU 



We can avoid unnecessary fpu load when userspace process
didn't use FPU frequently.

Derived from Avi's idea.

Signed-off-by: default avatarSheng Yang <sheng@linux.intel.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 5ee481da

arch/x86/include/asm/kvm_host.h

+0 −1
Original line number Diff line number Diff line
@@ -301,7 +301,6 @@ struct kvm_vcpu_arch { 
		unsigned long mmu_seq;

	} update_pte;



	struct i387_fxsave_struct host_fx_image;

	struct i387_fxsave_struct guest_fx_image;



	gva_t mmio_fault_cr2;

arch/x86/kvm/x86.c

+2 −16
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ 
#include <asm/desc.h>

#include <asm/mtrr.h>

#include <asm/mce.h>

#include <asm/i387.h>



#define MAX_IO_MSRS 256

#define CR0_RESERVED_BITS						\
@@ -5134,21 +5135,10 @@ void fx_init(struct kvm_vcpu *vcpu) 
{

	unsigned after_mxcsr_mask;



	/*

	 * Touch the fpu the first time in non atomic context as if

	 * this is the first fpu instruction the exception handler

	 * will fire before the instruction returns and it'll have to

	 * allocate ram with GFP_KERNEL.

	 */

	if (!used_math())

		kvm_fx_save(&vcpu->arch.host_fx_image);



	/* Initialize guest FPU by resetting ours and saving into guest's */

	preempt_disable();

	kvm_fx_save(&vcpu->arch.host_fx_image);

	kvm_fx_finit();

	kvm_fx_save(&vcpu->arch.guest_fx_image);

	kvm_fx_restore(&vcpu->arch.host_fx_image);

	preempt_enable();



	vcpu->arch.cr0 |= X86_CR0_ET;
@@ -5165,7 +5155,7 @@ void kvm_load_guest_fpu(struct kvm_vcpu *vcpu) 
		return;



	vcpu->guest_fpu_loaded = 1;

	kvm_fx_save(&vcpu->arch.host_fx_image);

	unlazy_fpu(current);

	kvm_fx_restore(&vcpu->arch.guest_fx_image);

	trace_kvm_fpu(1);

}
@@ -5177,7 +5167,6 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu) 


	vcpu->guest_fpu_loaded = 0;

	kvm_fx_save(&vcpu->arch.guest_fx_image);

	kvm_fx_restore(&vcpu->arch.host_fx_image);

	++vcpu->stat.fpu_reload;

	set_bit(KVM_REQ_DEACTIVATE_FPU, &vcpu->requests);

	trace_kvm_fpu(0);
@@ -5203,9 +5192,6 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu) 
{

	int r;



	/* We do fxsave: this must be aligned. */

	BUG_ON((unsigned long)&vcpu->arch.host_fx_image & 0xF);



	vcpu->arch.mtrr_state.have_fixed = 1;

	vcpu_load(vcpu);

	r = kvm_arch_vcpu_reset(vcpu);