From: Zachary Amsden i386 arch cleanup. Introduce the serialize macro to serialize processor state. Why the microcode update needs it I am not quite sure, since wrmsr() is already a serializing instruction, but it is a microcode update, so I will keep the semantic the same, since this could be a timing workaround. As far as I can tell, this has always been there since the original microcode update source. Signed-off-by: Zachary Amsden Signed-off-by: Andrew Morton --- arch/i386/kernel/microcode.c | 7 +++++-- include/asm-i386/processor.h | 5 +++++ 2 files changed, 10 insertions(+), 2 deletions(-) diff -puN arch/i386/kernel/microcode.c~i386-arch-cleanup-seralize-msr arch/i386/kernel/microcode.c --- devel/arch/i386/kernel/microcode.c~i386-arch-cleanup-seralize-msr 2005-07-30 11:15:44.000000000 -0700 +++ devel-akpm/arch/i386/kernel/microcode.c 2005-07-30 11:15:44.000000000 -0700 @@ -164,7 +164,8 @@ static void collect_cpu_info (void *unus } wrmsr(MSR_IA32_UCODE_REV, 0, 0); - __asm__ __volatile__ ("cpuid" : : : "ax", "bx", "cx", "dx"); + /* see notes above for revision 1.07. Apparent chip bug */ + serialize_cpu(); /* get the current revision from MSR 0x8B */ rdmsr(MSR_IA32_UCODE_REV, val[0], uci->rev); pr_debug("microcode: collect_cpu_info : sig=0x%x, pf=0x%x, rev=0x%x\n", @@ -377,7 +378,9 @@ static void do_update_one (void * unused (unsigned long) uci->mc->bits >> 16 >> 16); wrmsr(MSR_IA32_UCODE_REV, 0, 0); - __asm__ __volatile__ ("cpuid" : : : "ax", "bx", "cx", "dx"); + /* see notes above for revision 1.07. Apparent chip bug */ + serialize_cpu(); + /* get the current revision from MSR 0x8B */ rdmsr(MSR_IA32_UCODE_REV, val[0], val[1]); diff -puN include/asm-i386/processor.h~i386-arch-cleanup-seralize-msr include/asm-i386/processor.h --- devel/include/asm-i386/processor.h~i386-arch-cleanup-seralize-msr 2005-07-30 11:15:44.000000000 -0700 +++ devel-akpm/include/asm-i386/processor.h 2005-07-30 11:15:44.000000000 -0700 @@ -277,6 +277,11 @@ static inline void clear_in_cr4 (unsigne outb((data), 0x23); \ } while (0) +static inline void serialize_cpu(void) +{ + __asm__ __volatile__ ("cpuid" : : : "ax", "bx", "cx", "dx"); +} + static inline void __monitor(const void *eax, unsigned long ecx, unsigned long edx) { _