[src/trunk]: src/sys/arch/x86/x86 Optimize FNSAVE. The size of its save area ...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/f83d9ffac311
branches:  trunk
changeset: 362903:f83d9ffac311
user:      maxv <maxv%NetBSD.org@localhost>
date:      Sun Jul 01 07:59:30 2018 +0000

description:
Optimize FNSAVE. The size of its save area is 108 bytes, so don't set
x86_fpu_save_size = 512, because otherwise we uselessly memset extra
bytes at execve time.

While here use sizeof instead of hardcoded values.

diffstat:

 sys/arch/x86/x86/identcpu.c |  15 ++++++++-------
 1 files changed, 8 insertions(+), 7 deletions(-)

diffs (60 lines):

diff -r 8b3772c34d79 -r f83d9ffac311 sys/arch/x86/x86/identcpu.c
--- a/sys/arch/x86/x86/identcpu.c       Sun Jul 01 07:18:56 2018 +0000
+++ b/sys/arch/x86/x86/identcpu.c       Sun Jul 01 07:59:30 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: identcpu.c,v 1.77 2018/06/23 10:30:22 jdolecek Exp $   */
+/*     $NetBSD: identcpu.c,v 1.78 2018/07/01 07:59:30 maxv Exp $       */
 
 /*-
  * Copyright (c) 1999, 2000, 2001, 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: identcpu.c,v 1.77 2018/06/23 10:30:22 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: identcpu.c,v 1.78 2018/07/01 07:59:30 maxv Exp $");
 
 #include "opt_xen.h"
 
@@ -66,7 +66,7 @@
 char cpu_brand_string[49];
 
 int x86_fpu_save __read_mostly;
-unsigned int x86_fpu_save_size __read_mostly = 512;
+unsigned int x86_fpu_save_size __read_mostly = sizeof(struct save87);
 uint64_t x86_xsave_features __read_mostly = 0;
 
 /*
@@ -768,7 +768,7 @@
 
        x86_fpu_save = FPU_SAVE_FSAVE;
 
-#ifdef i386 /* amd64 always has fxsave, sse and sse2 */
+#ifdef i386
        /* If we have FXSAVE/FXRESTOR, use them. */
        if ((ci->ci_feat_val[0] & CPUID_FXSR) == 0) {
                i386_use_fxsave = 0;
@@ -789,11 +789,12 @@
 #else
        /*
         * For amd64 i386_use_fxsave, i386_has_sse and i386_has_sse2 are
-        * #defined to 1.
+        * #defined to 1, because fxsave/sse/sse2 are always present.
         */
-#endif /* i386 */
+#endif
 
        x86_fpu_save = FPU_SAVE_FXSAVE;
+       x86_fpu_save_size = sizeof(struct fxsave);
 
        /* See if xsave (for AVX) is supported */
        if ((ci->ci_feat_val[1] & CPUID2_XSAVE) == 0)
@@ -822,7 +823,7 @@
 
        /* Get features and maximum size of the save area */
        x86_cpuid(0xd, descs);
-       if (descs[2] > 512)
+       if (descs[2] > sizeof(struct fxsave))
                x86_fpu_save_size = descs[2];
 
        x86_xsave_features = (uint64_t)descs[3] << 32 | descs[0];