KVM: Use alignment properties of vcpu to simplify FPU ops
Now we use a kmem cache for allocating vcpus, we can get the 16-byte
alignment required by fxsave & fxrstor instructions, and avoid
manually aligning the buffer.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 4166a08..bfb1b6d 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -154,8 +154,8 @@
return;
vcpu->guest_fpu_loaded = 1;
- fx_save(vcpu->host_fx_image);
- fx_restore(vcpu->guest_fx_image);
+ fx_save(&vcpu->host_fx_image);
+ fx_restore(&vcpu->guest_fx_image);
}
EXPORT_SYMBOL_GPL(kvm_load_guest_fpu);
@@ -165,8 +165,8 @@
return;
vcpu->guest_fpu_loaded = 0;
- fx_save(vcpu->guest_fx_image);
- fx_restore(vcpu->host_fx_image);
+ fx_save(&vcpu->guest_fx_image);
+ fx_restore(&vcpu->host_fx_image);
}
EXPORT_SYMBOL_GPL(kvm_put_guest_fpu);
@@ -262,10 +262,6 @@
}
vcpu->pio_data = page_address(page);
- vcpu->host_fx_image = (char*)ALIGN((hva_t)vcpu->fx_buf,
- FX_IMAGE_ALIGN);
- vcpu->guest_fx_image = vcpu->host_fx_image + FX_IMAGE_SIZE;
-
r = kvm_mmu_create(vcpu);
if (r < 0)
goto fail_free_pio_data;
@@ -615,30 +611,20 @@
void fx_init(struct kvm_vcpu *vcpu)
{
- struct __attribute__ ((__packed__)) fx_image_s {
- u16 control; //fcw
- u16 status; //fsw
- u16 tag; // ftw
- u16 opcode; //fop
- u64 ip; // fpu ip
- u64 operand;// fpu dp
- u32 mxcsr;
- u32 mxcsr_mask;
-
- } *fx_image;
+ unsigned after_mxcsr_mask;
/* Initialize guest FPU by resetting ours and saving into guest's */
preempt_disable();
- fx_save(vcpu->host_fx_image);
+ fx_save(&vcpu->host_fx_image);
fpu_init();
- fx_save(vcpu->guest_fx_image);
- fx_restore(vcpu->host_fx_image);
+ fx_save(&vcpu->guest_fx_image);
+ fx_restore(&vcpu->host_fx_image);
preempt_enable();
- fx_image = (struct fx_image_s *)vcpu->guest_fx_image;
- fx_image->mxcsr = 0x1f80;
- memset(vcpu->guest_fx_image + sizeof(struct fx_image_s),
- 0, FX_IMAGE_SIZE - sizeof(struct fx_image_s));
+ after_mxcsr_mask = offsetof(struct i387_fxsave_struct, st_space);
+ vcpu->guest_fx_image.mxcsr = 0x1f80;
+ memset((void *)&vcpu->guest_fx_image + after_mxcsr_mask,
+ 0, sizeof(struct i387_fxsave_struct) - after_mxcsr_mask);
}
EXPORT_SYMBOL_GPL(fx_init);
@@ -2356,6 +2342,9 @@
preempt_notifier_init(&vcpu->preempt_notifier, &kvm_preempt_ops);
+ /* We do fxsave: this must be aligned. */
+ BUG_ON((unsigned long)&vcpu->host_fx_image & 0xF);
+
vcpu_load(vcpu);
r = kvm_mmu_setup(vcpu);
vcpu_put(vcpu);
@@ -2468,7 +2457,7 @@
static int kvm_vcpu_ioctl_get_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
{
- struct fxsave *fxsave = (struct fxsave *)vcpu->guest_fx_image;
+ struct fxsave *fxsave = (struct fxsave *)&vcpu->guest_fx_image;
vcpu_load(vcpu);
@@ -2488,7 +2477,7 @@
static int kvm_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
{
- struct fxsave *fxsave = (struct fxsave *)vcpu->guest_fx_image;
+ struct fxsave *fxsave = (struct fxsave *)&vcpu->guest_fx_image;
vcpu_load(vcpu);