[This is a repost with a more descriptive subject.]
I run dosemu 1.0.2.1 on the 2.5.x kernels. Upgrading from 2.5.64 to
2.5.65 (or 2.5.66) causes dosemu to no longer work: it locks up the
machine shortly after I run it. Alt-Sysrq still works OK. I traced the
problem to the "Cache MSR_IA32_SYSENTER_CS value in the per-CPU TSS"
changeset introduced in 2.5.65-bk5, which I have included as a patch
below. Backing this patch out from 2.5.65-bk5 makes dosemu work again.
Any idea what is going on?
Cheers, 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 { \
On Mon, 31 Mar 2003, Wayne Whitney wrote:
>
> I run dosemu 1.0.2.1 on the 2.5.x kernels. Upgrading from 2.5.64 to
> 2.5.65 (or 2.5.66) causes dosemu to no longer work: it locks up the
> machine shortly after I run it.
There appears to be at least one bug (that is longstanding but might be
made worse by the MSR stuff). However, that one should matter only with
preemption enabled. What's your configuration?
Also, do you actually have a new library that uses SYSENTER (ie recent
redhat beta), and whct kind of CPU do you have?
Linus
----
===== arch/i386/kernel/vm86.c 1.21 vs edited =====
--- 1.21/arch/i386/kernel/vm86.c Sun Mar 9 18:49:37 2003
+++ edited/arch/i386/kernel/vm86.c Mon Mar 31 11:23:50 2003
@@ -289,9 +289,10 @@
asm volatile("movl %%fs,%0":"=m" (tsk->thread.saved_fs));
asm volatile("movl %%gs,%0":"=m" (tsk->thread.saved_gs));
- tss = init_tss + smp_processor_id();
+ tss = init_tss + get_cpu();
tss->esp0 = tsk->thread.esp0 = (unsigned long) &info->VM86_TSS_ESP0;
disable_sysenter(tss);
+ put_cpu();
tsk->thread.screen_bitmap = info->screen_bitmap;
if (info->flags & VM86_SCREEN_BITMAP)
On Mon, 31 Mar 2003, Linus Torvalds wrote:
> On Mon, 31 Mar 2003, Wayne Whitney wrote:
> >
> > I run dosemu 1.0.2.1 on the 2.5.x kernels. Upgrading from 2.5.64 to
> > 2.5.65 (or 2.5.66) causes dosemu to no longer work: it locks up the
> > machine shortly after I run it.
>
> There appears to be at least one bug (that is longstanding but might be
> made worse by the MSR stuff). However, that one should matter only with
> preemption enabled. What's your configuration?
UP with preempt. 2.5.66 with the patch you sent still locks up. I should
mention that I am running two copies of a hacked XFree86 on two different
sets of KVM hardware, but that doesn't require any kernel patches (well, a
small one to the input layer).
> Also, do you actually have a new library that uses SYSENTER (ie recent
> redhat beta), and whct kind of CPU do you have?
Well, I have glibc-2.3.1-51, from RedHat Rawhide February 20, so it sounds
like that uses SYSENTER. The CPU is an Althon XP, stepping 6-6-2.
Cheers, Wayne
On Mon, 31 Mar 2003, Wayne Whitney wrote:
>
> UP with preempt. 2.5.66 with the patch you sent still locks up. I should
> mention that I am running two copies of a hacked XFree86 on two different
> sets of KVM hardware, but that doesn't require any kernel patches (well, a
> small one to the input layer).
Can you check dosemu in text mode to see if the kernel prints out
anything. I realize that not many things are relevant in text mode, but I
have this memory of dosemu at least historically supporting it. Maybe not
any more.
Linus
On Mon, 31 Mar 2003, Linus Torvalds wrote:
> Can you check dosemu in text mode to see if the kernel prints out
> anything. I realize that not many things are relevant in text mode, but
> I have this memory of dosemu at least historically supporting it. Maybe
> not any more.
OK, running dosemu at the console does not cause a lock up. More
specifically: just running dosemu doesn't cause a lock up ever. To get
it to lock up, I have to run this game I play. Under X, just running the
game and waiting at the game's main menu causes the lock up in a couple
minutes. At the console, the game's graphics mode is not supported, so I
get a blank screen. But if I run the game blind and wait at the main
menu, there is never a lock up.
Also, it seems that turning off preempt makes the problem go away. At
least, I haven't got any lockups yet.
Cheers, Wayne