linux-kernel - Re: [PATCH v2 6/9] Revert "iommu/arm-smmu: Make arm-smmu-v3 explicitly non-modular"

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Message-ID: <20191108173248.GA22448@willie-the-truck>
Date:   Fri, 8 Nov 2019 17:32:48 +0000
From:   Will Deacon <will@...nel.org>
To:     John Garry <john.garry@...wei.com>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        "Isaac J. Manjarres" <isaacm@...eaurora.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Saravana Kannan <saravanak@...gle.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH v2 6/9] Revert "iommu/arm-smmu: Make arm-smmu-v3
 explicitly non-modular"

On Fri, Nov 08, 2019 at 05:25:09PM +0000, John Garry wrote:
> On 08/11/2019 16:47, Will Deacon wrote:
> > On Fri, Nov 08, 2019 at 04:44:25PM +0000, John Garry wrote:
> > > BTW, it now looks like it was your v1 series I was testing there, on your
> > > branch iommu/module. It would be helpful to update for ease of testing.
> > 
> > Yes, sorry about that. I'll update it now (although I'm not sure it will
> > help with this -- I was going to see what happens with other devices such
> > as the intel-iommu or storage controllers)
> 
> So I tried your v2 series for this - it has the same issue, as I
> anticipated.

Right, I'm just not sure how resilient drivers are expected to be to force
unbinding like this. You can break lots of stuff with root...

> It seems that some iommu drivers do call iommu_device_register(), so maybe a
> decent reference. Or simply stop the driver being unbound.

I'm not sure what you mean about iommu_device_register() (we call that
already), but I guess we can keep the '.suppress_bind_attrs = true' if
necessary. I'll have a play on my laptop and see how well that works if
you start unbinding stuff.

Will