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Re: [PATCH v3 11/11] hw/arm/smmuv3: Advertise SMMUv3.2 range invalidatio

From: Auger Eric
Subject: Re: [PATCH v3 11/11] hw/arm/smmuv3: Advertise SMMUv3.2 range invalidation
Date: Fri, 10 Jul 2020 12:05:04 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0

Hi Peter,

On 7/10/20 11:47 AM, Peter Maydell wrote:
> On Wed, 8 Jul 2020 at 15:20, Eric Auger <eric.auger@redhat.com> wrote:
>> Expose the RIL bit so that the guest driver uses range
>> invalidation. Range invalidation being an SMMU3.2 feature,
>> let AIDR advertise SMMUv3.2 support.
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> I think that to advertise SMMUv3.2 we would also need to
> set the IDR3.BBML field to something non-zero. That means
> we need to analyze our implementation of the caching of page
> table structures to see if we need to do anything different
> (per the behaviours and guarantees described in section 3.21.1
> of the spec).
you're right. I need to further study this feature.

I felt difficult to find out which features are mandatory for a given
revision number.
> Alternatively, we could take advantage of the language
> in section 2.5 that says that a v3.x implementation is
> allowed to implement features from v3.(x+1), and just
> set the RIL bit while leaving AIDR advertising us as v3.1.
Indeed :-)

Thank you for the review!

> thanks
> -- PMM

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