Hi Yasser,

I hit the same CR4 PKE-bit case as you did a month ago.

May I ask you to resend the patch (with a Signed-Off line) to the
mailing list?

Thanks
  Ralf

On 5/21/19 6:38 PM, Jan Kiszka wrote:
> On 21.05.19 17:55, Ralf Ramsauer wrote:
>>
>>
>> On 5/21/19 5:09 PM, Jan Kiszka wrote:
>>> On 21.05.19 15:45, Ralf Ramsauer wrote:
>>>> Hi,
>>>>
>>>> we have some issues enabling Jailhouse on a Intel with a pretty new CPU
>>>> (Xeon Gold 5118).
>>>>
>>>> First, the CPU supports PKE and Linux will enable it (CR4, Bit 22).
>>>> Jailhouse won't start, as this bit is marked in X86_CR4_RESERVED.
>>>> Didn't
>>>> have a deeper look into this on how it affects the hypervisor or
>>>> allowing it needs some special treatment, so adding nopku to the
>>>> commandline will keep the feature disabled and suffices for the moment.
>>>>
>>>
>>> Known issue, see https://github.com/siemens/jailhouse/pull/23
>>
>> Aah, I remember that discussion a month ago...
>>
>> So I guess it is okay to allow this feature.
>>
>> What would you say, is it better to use a configuration parameter that
>> indicates the existence of PKE (as noted in the github discussion, we
>> should only respect that bit if available), or online cpuid discovery?
>>
>> I guess the latter one is a bit against the philosophy, but much simpler
>> to implement.
>>
> 
> Checking the code again and the comment I wrote around it, my remark in
> github that we would need discovery was actually overkill: The whole
> purpose of X86_CR4_RESERVED is to filter out future unknown bits. But
> CR4.PKE is no longer unknown, and it is apparently safe to allow it to
> the root cell. IOW, that commit was fine (if it had been submitted with
> signed-off here).
> 
> Jan
> 

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