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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: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Sheng Yang 2010-05-17 17:08:27 +08:00 committed by Avi Kivity
parent 5ee481da7b
commit 7cf30855e0
2 changed files with 2 additions and 17 deletions
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1
arch/x86/include/asm/kvm_host.h
View File

@ -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;

18
arch/x86/kvm/x86.c
View File

@ -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);