From: Will Deacon <will@kernel.org>
To: Vladimir Oltean <vladimir.oltean@nxp.com>
Cc: Robin Murphy <robin.murphy@arm.com>,
joro@8bytes.org, iommu@lists.linux.dev,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] iommu/arm-smmu: Report IOMMU_CAP_CACHE_COHERENCY even betterer
Date: Tue, 10 Jan 2023 11:10:50 +0000 [thread overview]
Message-ID: <20230110111049.GA8986@willie-the-truck> (raw)
In-Reply-To: <20230110105625.ououvyfj2g6ttkmf@skbuf>
On Tue, Jan 10, 2023 at 12:56:25PM +0200, Vladimir Oltean wrote:
> On Thu, Dec 15, 2022 at 04:51:55PM +0000, Robin Murphy wrote:
> > Although it's vanishingly unlikely that anyone would integrate an SMMU
> > within a coherent interconnect without also making the pagetable walk
> > interface coherent, the same effect happens if a coherent SMMU fails to
> > advertise CTTW correctly. This turns out to be the case on some popular
> > NXP SoCs, where VFIO started failing the IOMMU_CAP_CACHE_COHERENCY test,
> > even though IOMMU_CACHE *was* previously achieving the desired effect
> > anyway thanks to the underlying integration.
> >
> > While those SoCs stand to gain some more general benefits from a
> > firmware update to override CTTW correctly in DT/ACPI, it's also easy
> > to work around this in Linux as well, to avoid imposing too much on
> > affected users - since the upstream client devices *are* correctly
> > marked as coherent, we can trivially infer their coherent paths through
> > the SMMU as well.
> >
> > Reported-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> > Fixes: df198b37e72c ("iommu/arm-smmu: Report IOMMU_CAP_CACHE_COHERENCY better")
> > Signed-off-by: Robin Murphy <robin.murphy@arm.com>
> > ---
>
> Could someone please apply this patch?
Sorry, I missed that this was fixing a recent regression. I'll pick it up
today and send it to Joerg.
Will
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next prev parent reply other threads:[~2023-01-10 11:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-15 16:51 [PATCH] iommu/arm-smmu: Report IOMMU_CAP_CACHE_COHERENCY even betterer Robin Murphy
2022-12-19 12:03 ` Vladimir Oltean
2023-01-10 10:56 ` Vladimir Oltean
2023-01-10 11:10 ` Will Deacon [this message]
2023-01-10 14:02 ` Will Deacon
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