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Re: [Xen-devel] [PATCH v1] x86/altp2m: Add hypercall to create a new view and set sve bits




On 23.10.2019 14:58, Roger Pau Monné wrote:
> On Wed, Oct 23, 2019 at 09:11:54AM +0000, Alexandru Stefan ISAILA wrote:
>>
>>
>> On 03.09.2019 20:24, Tamas K Lengyel wrote:
>>> On Tue, Sep 3, 2019 at 9:53 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>>>
>>>> On 02.09.2019 10:11, Alexandru Stefan ISAILA wrote:
>>>>> --- a/xen/include/public/hvm/hvm_op.h
>>>>> +++ b/xen/include/public/hvm/hvm_op.h
>>>>> @@ -244,6 +244,7 @@ struct xen_hvm_altp2m_view {
>>>>>        /* Create view only: default access type
>>>>>         * NOTE: currently ignored */
>>>>>        uint16_t hvmmem_default_access; /* xenmem_access_t */
>>>>> +    uint8_t set_sve; /* bool value */
>>>>>    };
>>>>
>>>> This interface is, given the right configuration, available to
>>>> guests. Hence you can't simply add a field here. Just consider
>>>> what happens for an existing caller when there is random data
>>>> in the field you now assign a meaning.
>>>
>>> Perhaps instead of extending the HVMOP it would make more sense to
>>> just add a xl config option that defines the "default" sve bit for
>>> altp2m views in the domain?
>>>
>>
>> Adding a xl config option will not work for systems that do use xl.
>> There is a need that this will work in all cases.
> 
> I assume that such option would be implemented using a DOMCTL, which
> can also be used by other toolstacks. I however have no idea whether
> this is a suitable interface or not for this feature.
> 

I think that having a HVMOP_altp2m_get_suppress_ve_multi and letting the 
caller provide the start gfn and the nr of pages to have the sve bits 
set will provide a good solution for init an dfor further development.

I will go on this way for version 2 if everyone is ok with this.

Thanks,
Alex
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