linux-kernel - Re: [PATCH v5 5/9] iommu/arm-smmu-v3: Refactor write_ctx

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Message-ID: <20230815101911.GA11399@willie-the-truck>
Date:   Tue, 15 Aug 2023 11:19:11 +0100
From:   Will Deacon <will@...nel.org>
To:     Michael Shavit <mshavit@...gle.com>
Cc:     iommu@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, robin.murphy@....com,
        nicolinc@...dia.com, jgg@...dia.com, jean-philippe@...aro.org
Subject: Re: [PATCH v5 5/9] iommu/arm-smmu-v3: Refactor write_ctx_desc

On Tue, Aug 15, 2023 at 01:04:43PM +0800, Michael Shavit wrote:
> On Thu, Aug 10, 2023 at 5:15 PM Michael Shavit <mshavit@...gle.com> wrote:
> > On Wed, Aug 9, 2023 at 9:50 PM Will Deacon <will@...nel.org> wrote:
> > >
> > > Since you're dropping this and relying on the lock being taken higher up
> > > callstack, can we add a lockdep assertion that we do actually hold the
> > > devices_lock, please?
> >
> > Will do!
> 
> I spoke too soon; the point of this change was to remove the
> dependency on the arm_smmu_domain, piping the devices_lock would
> defeat this. In fact, this section is really depending on the iommu
> group lock not the devices_lock.

Sorry, but I'm not following you here. What is the devices_lock protecting
if we're depending on the group lock?

Will