x86:xsaveopt: Enable xsaveopt feature in Xen and guest

This patch uses "xsaveopt" instead of "xsave" if the feature is
supported in hardware to optimize task switch performance in Xen. It
also exposes the feature to guest VMs.

Signed-off-by: Zhang Fengzhe <fengzhe.zhang@intel.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/xen/include/asm-x86/i387.h b/xen/include/asm-x86/i387.h
index 0e01d1604d..471747c7c4 100644
--- a/xen/include/asm-x86/i387.h
+++ b/xen/include/asm-x86/i387.h
@@ -16,6 +16,7 @@
 
 extern unsigned int xsave_cntxt_size;
 extern u64 xfeature_mask;
+extern bool_t cpu_has_xsaveopt;
 
 void xsave_init(void);
 int xsave_alloc_save_area(struct vcpu *v);
@@ -28,6 +29,7 @@ void xsave_free_save_area(struct vcpu *v);
 #define XCNTXT_MASK     (XSTATE_FP | XSTATE_SSE | XSTATE_YMM)
 #define XSTATE_YMM_OFFSET  (512 + 64)
 #define XSTATE_YMM_SIZE    256
+#define XSAVEOPT        (1 << 0)
 
 struct xsave_struct
 {
@@ -84,6 +86,18 @@ static inline void xsave(struct vcpu *v)
         : "memory");
 }
 
+static inline void xsaveopt(struct vcpu *v)
+{
+    struct xsave_struct *ptr;
+
+    ptr =(struct xsave_struct *)v->arch.xsave_area;
+
+    asm volatile (".byte " REX_PREFIX "0x0f,0xae,0x37"
+        :
+        : "a" (-1), "d" (-1), "D"(ptr)
+        : "memory");
+}
+
 static inline void xrstor(struct vcpu *v)
 {
     struct xsave_struct *ptr;