Re: [PATCH][2.6-mm] Fix 4G/4G X11/vm86 oops

[Matt Mackall <mpm@selenic.com>]

On Wed, Nov 19, 2003 at 05:09:28PM -0600, Matt Mackall wrote:
> On Wed, Nov 19, 2003 at 02:32:10PM -0600, Matt Mackall wrote:
> > 
> > Zwane's got a K6-2 500MHz. I've just managed to reproduce this on my
> > 1.4GHz Opteron box (with Debian gcc 3.2). Here, the "ooh la la" bit
> > doesn't help. So my suspicion is that the printk is changing the
> > timing just enough on Zwane's box that he's getting a timer interrupt
> > knocking him out of vm86 mode before he hits a fatal bit in the fault
> > handling path for 4/4. Printks in handle_vm86_trap, handle_vm86_fault,
> > do_trap:vm86_trap, and do_general_protection:gp_in_vm86 never fire so
> > there's probably something amiss in the trampoline code.
> 
> Some more datapoints:
> 
> CPU          distro          compiler  video        X     result
> K6-2/500     connectiva 9    2.96      trident      4.3   reboot (zwane)
> K6-2/500     connectiva 9    3.2.2     trident      4.3   reboot (zwane)
> Opteron 240  debian unstable 3.2       S3           4.2.1 reboot
> Athlon 2100  debian unstable 3.2       radeon 7500  4.2.1 works
> P4M 1800     debian unstable 3.2       radeon m7    4.2.1 reboot

And indeed it does turn out to be a problem with the trampoline
mechanics. The fix for -mm4:


Fix triple faulting on some boxes with 4G/4G


 mm-mpm/arch/i386/kernel/vm86.c |    2 +-
 1 files changed, 1 insertion(+), 1 deletion(-)

diff -puN arch/i386/kernel/vm86.c~virtual-esp arch/i386/kernel/vm86.c
--- mm/arch/i386/kernel/vm86.c~virtual-esp	2003-11-20 01:36:32.000000000 -0600
+++ mm-mpm/arch/i386/kernel/vm86.c	2003-11-20 01:36:32.000000000 -0600
@@ -306,7 +306,7 @@ static void do_sys_vm86(struct kernel_vm
 	tss->esp0 = virtual_esp0(tsk);
 	if (cpu_has_sep)
 		tsk->thread.sysenter_cs = 0;
-	load_esp0(tss, &tsk->thread);
+	load_virtual_esp0(tss, tsk);
 	put_cpu();
 
 	tsk->thread.screen_bitmap = info->screen_bitmap;

_
 

-- 
Matt Mackall : http://www.selenic.com : Linux development and consulting