Messages in this thread | | | Date | Wed, 16 Jun 2021 12:28:03 +0530 | From | Sai Prakash Ranjan <> | Subject | Re: [PATCH] iommu/io-pgtable-arm: Optimize partial walk flush for large scatter-gather list |
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Hi Robin,
On 2021-06-15 19:23, Robin Murphy wrote: > On 2021-06-15 12:51, Sai Prakash Ranjan wrote:
<snip>...
>> Hi @Robin, from these discussions it seems they are not ok with the >> change >> for all SoC vendor implementations and do not have any data on such >> impact. >> As I mentioned above, on QCOM platforms we do have several >> optimizations in HW >> for TLBIs and would like to make use of it and reduce the unmap >> latency. >> What do you think, should this be made implementation specific? > > Yes, it sounds like there's enough uncertainty for now that this needs > to be an opt-in feature. However, I still think that non-strict mode > could use it generically, since that's all about over-invalidating to > save time on individual unmaps - and relatively non-deterministic - > already. > > So maybe we have a second set of iommu_flush_ops, or just a flag > somewhere to control the tlb_flush_walk functions internally, and the > choice can be made in the iommu_get_dma_strict() test, but also forced > on all the time by your init_context hook. What do you reckon? >
Sounds good to me. Since you mentioned non-strict mode using it generically, can't we just set tlb_flush_all() in io_pgtable_tlb_flush_walk() like below based on quirk so that we don't need to add any check in iommu_get_dma_strict() and just force the new flush_ops in init_context hook?
if (iop->cfg.quirks & IO_PGTABLE_QUIRK_NON_STRICT) { iop->cfg.tlb->tlb_flush_all(iop->cookie); return; }
Thanks, Sai
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