[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 { \
-
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This archive was generated by hypermail 2b29 : Mon Mar 31 2003 - 22:00:37 EST