Re: [PATCH] 2/6 i386 serialize-msr

[Zachary Amsden <zach@vmware.com>]

'Apparently' I need to make some coffee :)

Zwane Mwaikambo wrote:

> 	wrmsr(MSR_IA32_UCODE_REV, 0, 0);
> -	__asm__ __volatile__ ("cpuid" : : : "ax", "bx", "cx", "dx");
> +	/* see 1.07.  Apprent chip bug */
> +	serialize_cpu(); 
>
> 1.07 in which document? Also, please just spell 'apparent' correctly, 
> saving 1 byte really just looks lazy.
>
>  

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 <zach@vmware.com>
Index: linux-2.6.13/arch/i386/kernel/microcode.c
===================================================================
--- linux-2.6.13.orig/arch/i386/kernel/microcode.c	2005-07-29 15:26:04.000000000 -0700
+++ linux-2.6.13/arch/i386/kernel/microcode.c	2005-07-30 10:55:02.000000000 -0700
@@ -164,7 +164,8 @@
 	}
 
 	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 @@
 		(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]);
 
Index: linux-2.6.13/include/asm-i386/processor.h
===================================================================
--- linux-2.6.13.orig/include/asm-i386/processor.h	2005-07-29 15:26:53.000000000 -0700
+++ linux-2.6.13/include/asm-i386/processor.h	2005-07-30 10:32:44.000000000 -0700
@@ -277,6 +277,11 @@
 	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)
 {