Re: [PATCH] x86/amd: Fix xen_apic_write warnings in Dom0

[Wei Wang <wei.wang2@amd.com>]

On 10/15/2012 02:09 PM, Keir Fraser wrote:
> On 15/10/2012 12:12, "Jan Beulich"<JBeulich@suse.com>  wrote:
>
>>>>> On 09.10.12 at 10:06, Wei Wang<wei.wang2@amd.com>  wrote:
>>> --- a/xen/arch/x86/cpu/amd.c
>>> +++ b/xen/arch/x86/cpu/amd.c
>>> @@ -485,6 +485,17 @@ static void __devinit init_amd(struct cpuinfo_x86 *c)
>>> if (c->x86>  0x11)
>>> set_bit(X86_FEATURE_ARAT, c->x86_capability);
>>>
>>> + /*
>>> +  * Prior to Family 0x14, perf counters are not reset during warm reboot.
>>> +  * We have to reset them manually.
>>> +  */
>>> + if (c->x86<  0x14) {
>>> +  wrmsrl(MSR_K7_PERFCTR0, 0);
>>> +  wrmsrl(MSR_K7_PERFCTR1, 0);
>>> +  wrmsrl(MSR_K7_PERFCTR2, 0);
>>> +  wrmsrl(MSR_K7_PERFCTR3, 0);
>>> + }
>>
>> This collides with the NMI watchdog setup: smp_callin() calls
>> setup_local_APIC() _before_ calling smp_store_cpu_info(), and
>> hence you write zero again to an MSR possibly already in use.
>> Since setup_k7_watchdog() itself does the clearing of the MSRs
>> in question already, I would think that the most simple
>> adjustment to your patch would be to make the condition
>>
>> if (nmi_watchdog != NMI_LOCAL_APIC&&  c->x86<  0x14) {
>>
>> If you agree (and Keir doesn't object), I would commit it that way.
>
> Sounds good.
>
> Acked-by: Keir Fraser<keir@xen.org>

Sounds good to me too. Acked
Thanks,
Wei

>> Jan
>>
>>> +
>>> if (cpuid_edx(0x80000007)&  (1<<  10)) {
>>> rdmsr(MSR_K7_HWCR, l, h);
>>> l |= (1<<  27); /* Enable read-only APERF/MPERF bit */
>>
>>
>
>
>