Re: [PATCH 1/1] iommu/arm-smmu-v3: add support for BBML
From: Robin Murphy
Date: Thu Jan 28 2021 - 11:18:46 EST
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
.
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