Re: [PATCH v1 04/14] iommu/arm-smmu-v3: Add arm_smmu_hw_info

From: Nicolin Chen <nicolinc@nvidia.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: <jgg@nvidia.com>, <will@kernel.org>, <eric.auger@redhat.com>,
	<kevin.tian@intel.com>, <baolu.lu@linux.intel.com>,
	<joro@8bytes.org>, <shameerali.kolothum.thodi@huawei.com>,
	<jean-philippe@linaro.org>,
	<linux-arm-kernel@lists.infradead.org>, <iommu@lists.linux.dev>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v1 04/14] iommu/arm-smmu-v3: Add arm_smmu_hw_info
Date: Wed, 12 Apr 2023 00:47:21 -0700	[thread overview]
Message-ID: <ZDZiCUY25pix/NIX@Asurada-Nvidia> (raw)
In-Reply-To: <ZBN2tmWoRURvjarc@Asurada-Nvidia>

Hi Robin,

On Thu, Mar 16, 2023 at 01:06:17PM -0700, Nicolin Chen wrote:
> On Thu, Mar 16, 2023 at 03:19:27PM +0000, Robin Murphy wrote:
> 
> > > > Note that until now it has been extremely fortunate that in pretty much
> > > > every case Linux either hasn't supported the affected feature at all, or
> > > > has happened to avoid meeting the conditions. Once we do introduce
> > > > nesting support that all goes out the window (and I'll have to think
> > > > more when reviewing new errata in future...)
> > > > 
> > > > I've been putting off revisiting all the existing errata to figure out
> > > > what we'd need to do until new nesting patches appeared, so I'll try to
> > > > get to that soon now. I think in many cases it's likely to be best to
> > > > just disallowing nesting entirely on affected implementations.
> > > 
> > > Do we have already a list of "affected implementations"? Or,
> > > we would need to make such a list now? In a latter case, can
> > > these affected implementations be detected from their IRD0-5
> > > registers, so that we can simply do something in hw_info()?
> > 
> > Somewhere I have a patch that adds all the IIDR stuff needed for this,
> > but I never sent it upstream since the erratum itself was an early
> > MMU-600 one which in practice doesn't matter. I'll dig that out and
> > update it with what I have in mind.
> 
> Nice!
> 
> Perhaps we should merge that first, or include in this series
> if you don't mind, so that we would be less worried about any
> affected platform when releasing the new Linux version having
> this nesting feature.

I just want to see if there's a possibility of adding the
patch that you mentioned above in the near term?

I'd like to send a v2 of this series for another round of
review before the next -rc1, so it'd be nicer to include
that.

Thanks
Nic

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