Re: [Xen-devel] [PATCH v4 02/15] x86/cpu: Fix common cpuid faulting probing for AMD and Hygon

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.04.19 at 13:58, <puwen@xxxxxxxx> wrote:
> On 2019/4/2 18:20, Jan Beulich wrote:
>> On 02.04.19 at 08:46, <puwen@xxxxxxxx> wrote:
>>> On 2019/4/1 16:41, Jan Beulich wrote:
>>>> On 30.03.19 at 11:42, <puwen@xxxxxxxx> wrote:
>>>>> There is no MSR_INTEL_PLATFORM_INFO for AMD and Hygon families. So 
>>>>> directly
>>>>> return false in the function probe_cpuid_faulting() if 
>>>>> !cpu_has_hypervisor.
>>>>
>>>> I think it would have been nice if you had mentioned the real
>>>> reason why you want to bypass the MSR accesses. This way it
>>>> sounds as if the change was only cosmetic, and hence could be
>>>> left out.
>>>
>>> Okay, how about the new description:
>>> There is no MSR_INTEL_PLATFORM_INFO for AMD and Hygon families. Read
>>> this MSR will stop the Xen initialization process
>> 
>> "... for some early Hygon steppings"(?). I'm unaware of AMD CPUs
> 
> Yes,for some early Hygon steppings.
> 
>> having this issue - are you telling us otherwise?
> 
> I tested with an AMD CPU(Family 17h, Model 1, Stepping 1) today, and
> it also stopped when reading the MSR_INTEL_PLATFORM_INFO instead of
> producing #GP(0).

I've yet to try it out on my Rome system, but I have to admit I
find this hard to believe. Andrew - you've tried to boot Xen on a
Rome already. Iirc you said it crashed, but did it perhaps get to
(and past) this point?

Jan



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