x86, fpu: use non-lazy fpu restore for processors supporting xsave

[mirror_ubuntu-artful-kernel.git] / arch / x86 / kernel / i387.c

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index ab6a2e8028ae2fceafdbb171b2f3f8bc56cccfdd..528557470ddb4efcb8088c7ab29cc0295fb14cf6 100644 (file)
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -22,7 +22,15 @@
 /*
  * Were we in an interrupt that interrupted kernel mode?
  *
- * We can do a kernel_fpu_begin/end() pair *ONLY* if that
+ * For now, on xsave platforms we will return interrupted
+ * kernel FPU as not-idle. TBD: As we use non-lazy FPU restore
+ * for xsave platforms, ideally we can change the return value
+ * to something like __thread_has_fpu(current). But we need to
+ * be careful of doing __thread_clear_has_fpu() before saving
+ * the FPU etc for supporting nested uses etc. For now, take
+ * the simple route!
+ *
+ * On others, we can do a kernel_fpu_begin/end() pair *ONLY* if that
  * pair does nothing at all: the thread must not have fpu (so
  * that we don't try to save the FPU state), and TS must
  * be set (so that the clts/stts pair does nothing that is
@@ -30,6 +38,9 @@
  */
 static inline bool interrupted_kernel_fpu_idle(void)
 {
+       if (use_xsave())
+               return 0;
+
        return !__thread_has_fpu(current) &&
                (read_cr0() & X86_CR0_TS);
 }
@@ -73,7 +84,7 @@ void kernel_fpu_begin(void)
                __save_init_fpu(me);
                __thread_clear_has_fpu(me);
                /* We do 'stts()' in kernel_fpu_end() */
-       } else {
+       } else if (!use_xsave()) {
                this_cpu_write(fpu_owner_task, NULL);
                clts();
        }
@@ -82,7 +93,10 @@ EXPORT_SYMBOL(kernel_fpu_begin);
 
 void kernel_fpu_end(void)
 {
-       stts();
+       if (use_xsave())
+               math_state_restore();
+       else
+               stts();
        preempt_enable();
 }
 EXPORT_SYMBOL(kernel_fpu_end);