Add a clts() wrapper around the 'clts' instruction to <machine/cpufunc.h>

on x86 and use that to implement stop_emulating() in the fpu/npx code.
Reimplement start_emulating() in the non-XEN case by using load_cr0() and
rcr0() instead of the 'lmsw' and 'smsw' instructions.  Intel explicitly
discourages the use of 'lmsw' and 'smsw' on 80386 and later processors in
the description of these instructions in Volume 2 of the ADM.

Reviewed by:	kib
MFC after:	1 month

1 files changed, 10 insertions, 0 deletions

diff --git a/sys/i386/include/cpufunc.h b/sys/i386/include/cpufunc.h
index 7116f76..62d268d 100644
--- a/sys/i386/include/cpufunc.h
+++ b/sys/i386/include/cpufunc.h
@@ -97,6 +97,13 @@ clflush(u_long addr)
 }
 
 static __inline void
+clts(void)
+{
+
+	__asm __volatile("clts");
+}
+
+static __inline void
 disable_intr(void)
 {
 #ifdef XEN
@@ -688,6 +695,9 @@ intr_restore(register_t eflags)
 int	breakpoint(void);
 u_int	bsfl(u_int mask);
 u_int	bsrl(u_int mask);
+void	clflush(u_long addr);
+void	clts(void);
+void	cpuid_count(u_int ax, u_int cx, u_int *p);
 void	disable_intr(void);
 void	do_cpuid(u_int ax, u_int *p);
 void	enable_intr(void);