Date: Tue, 16 Jul 2013 07:07:16 +0900 From: Taku YAMAMOTO <taku@tackymt.homeip.net> To: freebsd-acpi@freebsd.org Subject: Revisiting FPU context resume on i386 Message-ID: <20130716070716.15b7282b9dca2cbc8a767631@tackymt.homeip.net>
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[-- Attachment #1 --]
Hi all,
sys/i386/i386/swtch.s have a big FIX ME in resumectx()
and I have occationally got bitten by it; resulting in SIGFPE disasters.
After cursory looking around FPU context, I think it's the simplest way
to set CR0_TS on resumectx() and to let npxdna() DTRT lazilly.
Attached is the mods that I'm currently using without a problem at the moment.
It at least doesn't interact with normal resume operations badly.
Ah, of cource, we have a choice to throw i386 away and get on amd64,
but at least I won't because I'd miss VOCALOIDs running on wine/i386 :)
--
-|-__ YAMAMOTO, Taku
| __ < <taku@tackymt.homeip.net>
- A chicken is an egg's way of producing more eggs. -
[-- Attachment #2 --]
commit 99a24d7c19d624654afbd574e604d8a011ed28b3
Author: Taku YAMAMOTO <taku@tackymt.homeip.net>
Date: Sun Jul 14 07:36:29 2013 +0900
i386: defer FPU context resume from resumectx() to npxdna() by CR0_TS.
diff --git a/sys/i386/i386/swtch.s b/sys/i386/i386/swtch.s
index 80aa6c4..71efae1 100644
--- a/sys/i386/i386/swtch.s
+++ b/sys/i386/i386/swtch.s
@@ -36,6 +36,7 @@
#include "opt_sched.h"
#include <machine/asmacros.h>
+#include <machine/specialreg.h>
#include "assym.s"
@@ -487,6 +488,10 @@ ENTRY(resumectx)
movl PCB_CR3(%ecx),%eax
movl %eax,%cr3
movl PCB_CR0(%ecx),%eax
+#ifdef DEV_NPX
+ /* Let npxdna() restore the FPU context lazily. */
+ orl $CR0_TS,%eax
+#endif
movl %eax,%cr0
jmp 1f
1:
@@ -519,10 +524,6 @@ ENTRY(resumectx)
movl PCB_DR7(%ecx),%eax
movl %eax,%dr7
-#ifdef DEV_NPX
- /* XXX FIX ME */
-#endif
-
/* Restore other registers */
movl PCB_EDI(%ecx),%edi
movl PCB_ESI(%ecx),%esi
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