linux-kernel - Re: [RFC PATCH v1 1/8] iommu/arm-smmu-v3: Add list of installed

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Message-ID: <CAKHBV243MUtVN8sf1O+u7Qseq-1YMmSdX-hVx0=t1o-9dni-WQ@mail.gmail.com>
Date:   Fri, 18 Aug 2023 13:34:53 +0800
From:   Michael Shavit <mshavit@...gle.com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     iommu@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, will@...nel.org, jgg@...dia.com,
        nicolinc@...dia.com, tina.zhang@...el.com, jean-philippe@...aro.org
Subject: Re: [RFC PATCH v1 1/8] iommu/arm-smmu-v3: Add list of installed_smmus

On Fri, Aug 18, 2023 at 3:34 AM Robin Murphy <robin.murphy@....com> wrote:
>
> On 2023-08-17 19:16, Michael Shavit wrote:
> > Add a new arm_smmu_installed_smmu class to aggregate masters belonging
> > to the same SMMU that a domain is attached to.
> > Update usages of the domain->devices list to first iterate over this
> > parent installed_smmus list.
> >
> > This allows functions that batch commands to an SMMU to first iterate
> > over the list of installed SMMUs before preparing the batched command
> > from the set of attached masters.
>
> I get the feeling that any purpose this serves could be achieved far
> more simply by just keeping the lists sorted by SMMU instance.

I initially tried just that, but then you need more sophisticated code
when iterating over the list to correctly batch operations by SMMU,
which is the more common operation.
That first hunk is very unfortunate though... Let me revive that
version and send it out so we can better compare.