Re: [PATCH][v2 3/3] KVM: x86: Use FPU API

[Avi Kivity]

On 05/17/2010 12:08 PM, Sheng Yang wrote:

Convert KVM to use generic FPU API.

  void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
  {
if (vcpu->guest_fpu_loaded)
@@ -5156,7 +5134,7 @@ void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)

vcpu->guest_fpu_loaded = 1;
unlazy_fpu(current);
-   kvm_fx_restore(&vcpu->arch.guest_fx_image);
+   fpu_restore_checking(&vcpu->arch.guest_fpu);
trace_kvm_fpu(1);
  }
   


Do we need to do something on error here?

I think an error can only occur if userspace sets bad fpu state, so 
maybe do the check in the ioctl.


In any case, unrelated to this patch.

--
Do not meddle in the internals of kernels, for they are subtle and quick to 
panic.

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[PATCH][v2 3/3] KVM: x86: Use FPU API

[Sheng Yang]

Convert KVM to use generic FPU API.

Signed-off-by: Sheng Yang 
---
 arch/x86/include/asm/kvm_host.h |   17 +
 arch/x86/kvm/x86.c  |   52 ---
 2 files changed, 17 insertions(+), 52 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d93601c..d08bb4a 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -301,7 +301,7 @@ struct kvm_vcpu_arch {
unsigned long mmu_seq;
} update_pte;
 
-   struct i387_fxsave_struct guest_fx_image;
+   struct fpu guest_fpu;
 
gva_t mmio_fault_cr2;
struct kvm_pio_request pio;
@@ -708,21 +708,6 @@ static inline unsigned long read_msr(unsigned long msr)
 }
 #endif
 
-static inline void kvm_fx_save(struct i387_fxsave_struct *image)
-{
-   asm("fxsave (%0)":: "r" (image));
-}
-
-static inline void kvm_fx_restore(struct i387_fxsave_struct *image)
-{
-   asm("fxrstor (%0)":: "r" (image));
-}
-
-static inline void kvm_fx_finit(void)
-{
-   asm("finit");
-}
-
 static inline u32 get_rdx_init_val(void)
 {
return 0x600; /* P6 family */
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ba8c2d2..7be1d36 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -53,6 +53,7 @@
 #include 
 #include 
 #include 
+#include 
 
 #define MAX_IO_MSRS 256
 #define CR0_RESERVED_BITS  \
@@ -5058,27 +5059,6 @@ out:
 }
 
 /*
- * fxsave fpu state.  Taken from x86_64/processor.h.  To be killed when
- * we have asm/x86/processor.h
- */
-struct fxsave {
-   u16 cwd;
-   u16 swd;
-   u16 twd;
-   u16 fop;
-   u64 rip;
-   u64 rdp;
-   u32 mxcsr;
-   u32 mxcsr_mask;
-   u32 st_space[32];   /* 8*16 bytes for each FP-reg = 128 bytes */
-#ifdef CONFIG_X86_64
-   u32 xmm_space[64];  /* 16*16 bytes for each XMM-reg = 256 bytes */
-#else
-   u32 xmm_space[32];  /* 8*16 bytes for each XMM-reg = 128 bytes */
-#endif
-};
-
-/*
  * Translate a guest virtual address to a guest physical address.
  */
 int kvm_arch_vcpu_ioctl_translate(struct kvm_vcpu *vcpu,
@@ -5101,7 +5081,8 @@ int kvm_arch_vcpu_ioctl_translate(struct kvm_vcpu *vcpu,
 
 int kvm_arch_vcpu_ioctl_get_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
 {
-   struct fxsave *fxsave = (struct fxsave *)&vcpu->arch.guest_fx_image;
+   struct i387_fxsave_struct *fxsave =
+   &vcpu->arch.guest_fpu.state->fxsave;
 
memcpy(fpu->fpr, fxsave->st_space, 128);
fpu->fcw = fxsave->cwd;
@@ -5117,7 +5098,8 @@ int kvm_arch_vcpu_ioctl_get_fpu(struct kvm_vcpu *vcpu, 
struct kvm_fpu *fpu)
 
 int kvm_arch_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
 {
-   struct fxsave *fxsave = (struct fxsave *)&vcpu->arch.guest_fx_image;
+   struct i387_fxsave_struct *fxsave =
+   &vcpu->arch.guest_fpu.state->fxsave;
 
memcpy(fxsave->st_space, fpu->fpr, 128);
fxsave->cwd = fpu->fcw;
@@ -5133,22 +5115,18 @@ int kvm_arch_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, 
struct kvm_fpu *fpu)
 
 void fx_init(struct kvm_vcpu *vcpu)
 {
-   unsigned after_mxcsr_mask;
-
-   /* Initialize guest FPU by resetting ours and saving into guest's */
-   preempt_disable();
-   kvm_fx_finit();
-   kvm_fx_save(&vcpu->arch.guest_fx_image);
-   preempt_enable();
+   fpu_alloc(&vcpu->arch.guest_fpu);
+   fpu_finit(&vcpu->arch.guest_fpu);
 
vcpu->arch.cr0 |= X86_CR0_ET;
-   after_mxcsr_mask = offsetof(struct i387_fxsave_struct, st_space);
-   vcpu->arch.guest_fx_image.mxcsr = 0x1f80;
-   memset((void *)&vcpu->arch.guest_fx_image + after_mxcsr_mask,
-  0, sizeof(struct i387_fxsave_struct) - after_mxcsr_mask);
 }
 EXPORT_SYMBOL_GPL(fx_init);
 
+static void fx_free(struct kvm_vcpu *vcpu)
+{
+   fpu_free(&vcpu->arch.guest_fpu);
+}
+
 void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
 {
if (vcpu->guest_fpu_loaded)
@@ -5156,7 +5134,7 @@ void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
 
vcpu->guest_fpu_loaded = 1;
unlazy_fpu(current);
-   kvm_fx_restore(&vcpu->arch.guest_fx_image);
+   fpu_restore_checking(&vcpu->arch.guest_fpu);
trace_kvm_fpu(1);
 }
 
@@ -5166,7 +5144,7 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
return;
 
vcpu->guest_fpu_loaded = 0;
-   kvm_fx_save(&vcpu->arch.guest_fx_image);
+   fpu_save_init(&vcpu->arch.guest_fpu);
++vcpu->stat.fpu_reload;
set_bit(KVM_REQ_DEACTIVATE_FPU, &vcpu->requests);
trace_kvm_fpu(0);
@@ -5179,6 +5157,7 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
vcpu->arch.time_page = NULL;
}
 
+   fx_free(vcpu);
kvm_x86_ops->vcpu_free(vcpu);
 }
 
@@ -5213,6 +5192,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
kvm_mmu_unload(vcpu);
vcp