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>

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 9f5784216c0d451e3544a4d0121654cc963ca2bc..19c8ba0794a84104c07e34a75328ea9f91c2beb0 100644 (file)
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -2171,6 +2171,9 @@ void hvm_cpuid(unsigned int input, unsigned int *eax, unsigned int *ebx,
                 *ebx = XSTATE_YMM_OFFSET;
                 break;
             case 1:
+                if ( cpu_has_xsaveopt )
+                    *eax = XSAVEOPT;
+                break;
             default:
                 break;
             }

diff --git a/xen/arch/x86/i387.c b/xen/arch/x86/i387.c
index 82dd88e92009554228e3889ecf69e74a1182bc63..1ddb2c7495872437892e5cde2365c1cfe8d11fb8 100644 (file)
--- a/xen/arch/x86/i387.c
+++ b/xen/arch/x86/i387.c
@@ -39,7 +39,10 @@ void save_init_fpu(struct vcpu *v)
          * we set all accumulated feature mask before doing save/restore.
          */
         set_xcr0(v->arch.xcr0_accum);
-        xsave(v);
+        if ( cpu_has_xsaveopt )
+            xsaveopt(v);
+        else
+            xsave(v);
         set_xcr0(v->arch.xcr0);
     }
     else if ( cpu_has_fxsr )
@@ -152,6 +155,8 @@ u64 xfeature_mask;
 /* Cached xcr0 for fast read */
 DEFINE_PER_CPU(uint64_t, xcr0);
 
+bool_t __read_mostly cpu_has_xsaveopt;
+
 void xsave_init(void)
 {
     u32 eax, ebx, ecx, edx;
@@ -196,6 +201,10 @@ void xsave_init(void)
         xfeature_mask &= XCNTXT_MASK;
         printk("%s: using cntxt_size: 0x%x and states: 0x%"PRIx64"\n",
             __func__, xsave_cntxt_size, xfeature_mask);
+
+        /* Check XSAVEOPT feature. */
+        cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
+        cpu_has_xsaveopt = !!(eax & XSAVEOPT);
     }
     else
     {

diff --git a/xen/include/asm-x86/i387.h b/xen/include/asm-x86/i387.h
index 0e01d1604d49d3a793a35adb32762334059e85f7..471747c7c478cdd8865abff041f71187084044b7 100644 (file)
--- 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;