Re: [PATCH RFC 04/10] intel_iommu: Second Stage Access Dirty bit support

[Joao Martins <joao.m.martins@oracle.com>]

On 5/5/22 08:41, Jason Wang wrote:
> On Wed, May 4, 2022 at 4:47 AM Joao Martins <joao.m.martins@oracle.com> wrote:
>>
>> On 4/29/22 19:21, Peter Xu wrote:
>>> On Fri, Apr 29, 2022 at 10:12:01AM +0100, Joao Martins wrote:
>>>> On 4/29/22 03:26, Jason Wang wrote:
>>>>> On Fri, Apr 29, 2022 at 5:14 AM Joao Martins <joao.m.martins@oracle.com> wrote:
>>>>>> @@ -3693,7 +3759,8 @@ static void vtd_init(IntelIOMMUState *s)
>>>>>>
>>>>>>      /* TODO: read cap/ecap from host to decide which cap to be exposed. */
>>>>>>      if (s->scalable_mode) {
>>>>>> -        s->ecap |= VTD_ECAP_SMTS | VTD_ECAP_SRS | VTD_ECAP_SLTS;
>>>>>> +        s->ecap |= VTD_ECAP_SMTS | VTD_ECAP_SRS | VTD_ECAP_SLTS |
>>>>>> +                   VTD_ECAP_SLADS;
>>>>>>      }
>>>>>
>>>>> We probably need a dedicated command line parameter and make it compat
>>>>> for pre 7.1 machines.
>>>>>
>>>>> Otherwise we may break migration.
>>>>
>>>> I can gate over an 'x-ssads' option (default disabled). Which reminds me that I probably
>>>> should rename to the most recent mnemonic (as SLADS no longer exists in manuals).
>>>>
>>>> If we all want by default enabled I can add a separate patch to do so.
>>>
>>> The new option sounds good.
>>>
>>
>> OK, I'll fix it then for the next iteration.
>>
>> Also, perhaps I might take the emulated iommu patches out of the iommufd stuff into a
>> separate series. There might be a place for them in the realm of testing/prototyping.
> 
> That would be better.
> 
OK, I'll do that then.

>> Perhaps best to see how close we are to spec is to check what we support in intel-iommu
>> in terms of VT-d revision versus how many buckets we fill in. I think SLADS/SSADS was in
>> 3.0 IIRC.
>>
>> I can take the compat stuff out if it's too early for that -- But I take it
>> these are questions for Jason.
>>
> 
> There's probably no need for the compat stuff, having a dedicated
> option and making it disabled by default should be fine.

/me nods