[src/trunk]: src/sys/arch/x86/x86 When using EagerFPU, create the fpu state i...

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

details:   https://anonhg.NetBSD.org/src/rev/d4e6b67fb3bb
branches:  trunk
changeset: 362646:d4e6b67fb3bb
user:      maxv <maxv%NetBSD.org@localhost>
date:      Tue Jun 19 09:25:13 2018 +0000

description:
When using EagerFPU, create the fpu state in execve at IPL_HIGH.

A preemption could occur in the middle, and we don't want that to happen,
because the context switch would use the partially-constructed fpu state.

The procedure becomes:

        splhigh
        unbusy the current cpu's fpu
        create a new fpu state in memory
        install the state on the current cpu's fpu
        splx

Disabling preemption also ensures that x86_fpu_eager doesn't change in
the middle.

In LazyFPU mode we drop IPL_HIGH right away.

Add more KASSERTs.

diffstat:

 sys/arch/x86/x86/fpu.c |  26 +++++++++++++++++---------
 1 files changed, 17 insertions(+), 9 deletions(-)

diffs (58 lines):

diff -r da56dc21adf6 -r d4e6b67fb3bb sys/arch/x86/x86/fpu.c
--- a/sys/arch/x86/x86/fpu.c    Tue Jun 19 09:20:46 2018 +0000
+++ b/sys/arch/x86/x86/fpu.c    Tue Jun 19 09:25:13 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: fpu.c,v 1.38 2018/06/18 20:20:27 maxv Exp $    */
+/*     $NetBSD: fpu.c,v 1.39 2018/06/19 09:25:13 maxv Exp $    */
 
 /*
  * Copyright (c) 2008 The NetBSD Foundation, Inc.  All
@@ -96,7 +96,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: fpu.c,v 1.38 2018/06/18 20:20:27 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: fpu.c,v 1.39 2018/06/19 09:25:13 maxv Exp $");
 
 #include "opt_multiprocessor.h"
 
@@ -624,10 +624,22 @@
 {
        union savefpu *fpu_save;
        struct pcb *pcb;
+       int s;
 
-       fpusave_lwp(l, false);
+       KASSERT(l == curlwp);
+       KASSERT((l->l_flag & LW_SYSTEM) == 0);
        fpu_save = process_fpframe(l);
        pcb = lwp_getpcb(l);
+
+       s = splhigh();
+       if (x86_fpu_eager) {
+               KASSERT(pcb->pcb_fpcpu == NULL ||
+                   pcb->pcb_fpcpu == curcpu());
+               fpusave_cpu(false);
+       } else {
+               splx(s);
+               fpusave_lwp(l, false);
+       }
        KASSERT(pcb->pcb_fpcpu == NULL);
 
        if (i386_use_fxsave) {
@@ -650,13 +662,9 @@
        }
        pcb->pcb_fpu_dflt_cw = x87_cw;
 
-       /*
-        * If using eager-switch, install the FPU state on the current
-        * CPU.
-        */
        if (x86_fpu_eager) {
-               KASSERT(l == curlwp);
-               fpu_eagerswitch(NULL, l);
+               fpu_eagerrestore(l);
+               splx(s);
        }
 }