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>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 0c06148..d93601c 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -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;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4c2096f..54ce775 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -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);