Re: AMD errata 169

On Fri, 26 Jun 2009 12:37:27 +0100
Ian J Hart <ianjhart_at_ntlworld.com> mentioned:

> I know I asked this before but I figure the long post may have put  
> some people off.
> 
> #169
> http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/25759.pdf
> 
> I'd like to eliminate this as a cause of my problem
> 
> It appears I can read the value.
> 
> #kldload cpuctl
> #cpucontrol -m 0xc001001f /dev/cpuctl0
> MSR 0xc001001f: 0x00400000 0x00100008
> 
> #cpucontrol -m 0xc001001f=0x0040000000100008 /dev/cpuctl0
> 
> Causes an nfe0 watchdog timeout and a powerdown failed, so that's  
> clearly a dumb thing to do.
> 
> Would I be better off asking somewhere else?

It looks like it is my fault in fact.  Due to the bug in cpuctl
code the value written to MSR registers always was zero.  Can you,
please, try with the following patch?  Thanks!

Index: sys/dev/cpuctl/cpuctl.c
===================================================================
--- sys/dev/cpuctl/cpuctl.c	(revision 195052)
+++ sys/dev/cpuctl/cpuctl.c	(working copy)
_at__at_ -222,14 +222,17 _at__at_
 	 * Explicitly clear cpuid data to avoid returning stale
 	 * info
 	 */
-	data->data = 0;
 	DPRINTF("[cpuctl,%d]: operating on MSR %#0x for %d cpu\n", __LINE__,
 	    data->msr, cpu);
 	oldcpu = td->td_oncpu;
 	is_bound = cpu_sched_is_bound(td);
 	set_cpu(cpu, td);
-	ret = cmd == CPUCTL_RDMSR ? rdmsr_safe(data->msr, &data->data) :
-	    wrmsr_safe(data->msr, data->data);
+	if (cmd == CPUCTL_RDMSR) {
+		data->data = 0;
+		ret = rdmsr_safe(data->msr, &data->data);
+	} else {
+		ret = wrmsr_safe(data->msr, data->data);
+	}
 	restore_cpu(oldcpu, is_bound, td);
 	return (ret);
 }
_at__at_ -368,7 +371,7 _at__at_
 	/*
 	 * Perform update.
 	 */
-	wrmsr_safe(MSR_K8_UCODE_UPDATE, (uintptr_t)args->data);
+	wrmsr_safe(MSR_K8_UCODE_UPDATE, (uintptr_t)ptr);
 
 	/*
 	 * Serialize instruction flow.

-- 
Stanislav Sedov
ST4096-RIPE