diff options
| author | Ben Hutchings <ben@decadent.org.uk> | 2009-09-10 02:53:50 +0100 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2009-09-10 16:50:19 -0700 |
| commit | 5367b6887e7d8c870a5da7d9b8c6e9c207684e43 (patch) | |
| tree | eab362078a7964850b00f8d781aa9c9f5ff01df7 /arch/x86/include/asm/processor.h | |
| parent | b19ae3999891cad21a3995c34d313dda5df014e2 (diff) | |
x86: Fix code patching for paravirt-alternatives on 486
As reported in <http://bugs.debian.org/511703> and
<http://bugs.debian.org/515982>, kernels with paravirt-alternatives
enabled crash in text_poke_early() on at least some 486-class
processors.
The problem is that text_poke_early() itself uses inline functions
affected by paravirt-alternatives and so will modify instructions that
have already been prefetched. Pentium and later processors will
invalidate the prefetched instructions in this case, but 486-class
processors do not.
Change sync_core() to limit prefetching on 486-class (and 386-class)
processors, and move the call to sync_core() above the call to the
modifiable local_irq_restore().
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
LKML-Reference: <1252547631.3423.134.camel@localhost>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86/include/asm/processor.h')
| -rw-r--r-- | arch/x86/include/asm/processor.h | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index c7768269b1c..2db56c57a28 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -703,13 +703,23 @@ static inline void cpu_relax(void) rep_nop(); } -/* Stop speculative execution: */ +/* Stop speculative execution and prefetching of modified code. */ static inline void sync_core(void) { int tmp; - asm volatile("cpuid" : "=a" (tmp) : "0" (1) - : "ebx", "ecx", "edx", "memory"); +#if defined(CONFIG_M386) || defined(CONFIG_M486) + if (boot_cpu_data.x86 < 5) + /* There is no speculative execution. + * jmp is a barrier to prefetching. */ + asm volatile("jmp 1f\n1:\n" ::: "memory"); + else +#endif + /* cpuid is a barrier to speculative execution. + * Prefetched instructions are automatically + * invalidated when modified. */ + asm volatile("cpuid" : "=a" (tmp) : "0" (1) + : "ebx", "ecx", "edx", "memory"); } static inline void __monitor(const void *eax, unsigned long ecx, |