Messages in this thread | | | Subject | Re: [PATCH 1/1] iommu/arm-smmu-v3: add support for BBML | From | Robin Murphy <> | Date | Thu, 28 Jan 2021 16:17:35 +0000 |
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On 2021-01-28 15:18, Keqian Zhu wrote: > > > On 2021/1/27 17:39, Robin Murphy wrote: >> On 2021-01-27 07:36, Keqian Zhu wrote: >>> >>> >>> On 2021/1/27 10:01, Leizhen (ThunderTown) wrote: >>>> >>>> >>>> On 2021/1/26 18:12, Will Deacon wrote: >>>>> On Mon, Jan 25, 2021 at 08:23:40PM +0000, Robin Murphy wrote: >>>>>> Now we probably will need some degreee of BBML feature awareness for the >>>>>> sake of SVA if and when we start using it for CPU pagetables, but I still >>>>>> cannot see any need to consider it in io-pgtable. >>>>> >>>>> Agreed; I don't think this is something that io-pgtable should have to care >>>>> about. >>> Hi, >>> >>> I have a question here :-). >>> If the old table is not live, then the break procedure seems unnecessary. Do I miss something? >> >> The MMU is allowed to prefetch translations at any time, so not following the proper update procedure could still potentially lead to a TLB conflict, even if there's no device traffic to worry about disrupting. >> >> Robin. > > Thanks. Does the MMU you mention here includes MMU and SMMU? I know that at SMMU side, ATS can prefetch translation.
Yes, both - VMSAv8 allows speculative translation table walks, so SMMUv3 inherits from there (per 3.21.1 "Translation tables and TLB invalidation completion behavior").
Robin.
> > Keqian >> >>> Thanks, >>> Keqian >>> >>>> >>>> Yes, the SVA works in stall mode, and the failed device access requests are not >>>> discarded. >>>> >>>> Let me look for examples. The BBML usage scenario was told by a former colleague. >>>> >>>>> >>>>> Will >>>>> >>>>> . >>>>> >>>> >>>> >>>> _______________________________________________ >>>> linux-arm-kernel mailing list >>>> linux-arm-kernel@lists.infradead.org >>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >>>> . >>>> >>> _______________________________________________ >>> iommu mailing list >>> iommu@lists.linux-foundation.org >>> https://lists.linuxfoundation.org/mailman/listinfo/iommu >>> >> . >>
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