2003-03-25 23:25:36

by Wayne Whitney

Subject: [BUG] 2.5.65 kills dosemu, 2.5.64 is OK

Hello all,

>From time to time I run an old DOS game under dosemu under X. In 2.5.64,
everything works fine. In 2.5.65, after about a minute, the display locks
up. Alt-Sysrq stills works OK. Before I start a binary search on the -bk
snapshots between 2.5.64 and 2.5.65, does anyone have a suggestion for the
culprit or a better debugging method?

Thanks, Wayne

2003-03-28 00:06:08

by Wayne Whitney

Subject: Re: [BUG] 2.5.65 kills dosemu, 2.5.64 is OK

On Tue, 25 Mar 2003, Wayne Whitney wrote:

> From time to time I run an old DOS game under dosemu under X. In 2.5.64,
> everything works fine. In 2.5.65, after about a minute, the display locks
> up. Alt-Sysrq stills works OK.

OK, I traced this problem to the "Cache the MSR_IA32_SYSENTER_CS value in
the per-CPU TSS" changeset from Linus, which is number 1.889.330.36 on
linus.bkbit.net/linux-2.5. This changeset first appeared in 2.5.64-bk5.
To be 100% clear, 2.5.64-bk4 doesn't have the problem, 2.5.65-bk5 does
have the problem, and 2.5.64-bk5 with the changeset reverted doesn't have
the problem.

Oh, I am running dosemu 1.0.2.1. For reference, the Changeset diff is
below. Any thoughts on why dosemu is no longer working for me?

Yours, Wayne


diff -ru linux-2.5.64-bk4/arch/i386/kernel/sysenter.c linux-2.5.64-bk5/arch/i386/kernel/sysenter.c
--- linux-2.5.64-bk4/arch/i386/kernel/sysenter.c 2003-03-26 21:06:54.000000000 -0800
+++ linux-2.5.64-bk5/arch/i386/kernel/sysenter.c 2003-03-26 13:55:08.000000000 -0800
@@ -40,6 +40,7 @@
int cpu = get_cpu();
struct tss_struct *tss = init_tss + cpu;

+ tss->ss1 = __KERNEL_CS;
wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
wrmsr(MSR_IA32_SYSENTER_ESP, tss->esp0, 0);
wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) sysenter_entry, 0);
diff -ru linux-2.5.64-bk4/arch/i386/kernel/vm86.c linux-2.5.64-bk5/arch/i386/kernel/vm86.c
--- linux-2.5.64-bk4/arch/i386/kernel/vm86.c 2003-03-26 21:06:54.000000000 -0800
+++ linux-2.5.64-bk5/arch/i386/kernel/vm86.c 2003-03-26 13:55:08.000000000 -0800
@@ -291,7 +291,7 @@

tss = init_tss + smp_processor_id();
tss->esp0 = tsk->thread.esp0 = (unsigned long) &info->VM86_TSS_ESP0;
- disable_sysenter();
+ disable_sysenter(tss);

tsk->thread.screen_bitmap = info->screen_bitmap;
if (info->flags & VM86_SCREEN_BITMAP)
diff -ru linux-2.5.64-bk4/include/asm-i386/processor.h linux-2.5.64-bk5/include/asm-i386/processor.h
--- linux-2.5.64-bk4/include/asm-i386/processor.h 2003-03-26 21:06:55.000000000 -0800
+++ linux-2.5.64-bk5/include/asm-i386/processor.h 2003-03-26 13:55:09.000000000 -0800
@@ -347,7 +347,7 @@
unsigned long esp0;
unsigned short ss0,__ss0h;
unsigned long esp1;
- unsigned short ss1,__ss1h;
+ unsigned short ss1,__ss1h; /* ss1 is used to cache MSR_IA32_SYSENTER_CS */
unsigned long esp2;
unsigned short ss2,__ss2h;
unsigned long __cr3;
@@ -413,15 +413,20 @@
{
tss->esp0 = esp0;
if (cpu_has_sep) {
- wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
+ if (tss->ss1 != __KERNEL_CS) {
+ tss->ss1 = __KERNEL_CS;
+ wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
+ }
wrmsr(MSR_IA32_SYSENTER_ESP, esp0, 0);
}
}

-static inline void disable_sysenter(void)
+static inline void disable_sysenter(struct tss_struct *tss)
{
- if (cpu_has_sep)
+ if (cpu_has_sep) {
+ tss->ss1 = 0;
wrmsr(MSR_IA32_SYSENTER_CS, 0, 0);
+ }
}

#define start_thread(regs, new_eip, new_esp) do { \