From: Jason Gunthorpe <jgg@nvidia.com>
To: Jonathan Cameron <jonathan.cameron@huawei.com>
Cc: Nicolin Chen <nicolinc@nvidia.com>,
will@kernel.org, robin.murphy@arm.com, bhelgaas@google.com,
joro@8bytes.org, praan@google.com, baolu.lu@linux.intel.com,
kevin.tian@intel.com, miko.lenczewski@arm.com,
linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
dan.j.williams@intel.com
Subject: Re: [PATCH v2 3/3] iommu/arm-smmu-v3: Allow ATS to be always on
Date: Tue, 24 Feb 2026 12:09:47 -0400 [thread overview]
Message-ID: <aZ3NS4GhxhElWhh2@nvidia.com> (raw)
In-Reply-To: <20260224155742.00000282@huawei.com>
On Tue, Feb 24, 2026 at 03:57:42PM +0000, Jonathan Cameron wrote:
> On Tue, 24 Feb 2026 10:51:02 -0400
> Jason Gunthorpe <jgg@nvidia.com> wrote:
>
> > On Tue, Feb 24, 2026 at 12:06:15PM +0000, Jonathan Cameron wrote:
> >
> > > In my head at least, it would be nice if a driver had to explicitly opt in
> > > to this behavior. The presence of CXL.cache support for instance doesn't
> > > actually mean the driver is going to enable it. However it is probably
> > > harmless so lets go with this as path of least resistance.
> >
> > That same remark applies to ATS in general, we have no idea if the
> > device is going to use it when turned on or not..
>
> Yup. Understood. That's the bit that smells bad to me.
Do you have thoughts on when this is a problem (aside from device
pre-acceptance security already discussed)? So far I haven't heard
complaining on this point..
Jason
next prev parent reply other threads:[~2026-02-24 16:09 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-23 22:52 [PATCH v2 0/3] Allow ATS to be always on for certain ATS-capable devices Nicolin Chen
2026-02-23 22:52 ` [PATCH v2 1/3] PCI: Allow ATS to be always on for CXL.cache capable devices Nicolin Chen
2026-02-24 11:55 ` Jonathan Cameron
2026-02-24 18:43 ` Nicolin Chen
2026-03-03 3:18 ` Baolu Lu
2026-03-03 20:15 ` Nicolin Chen
2026-02-23 22:52 ` [PATCH v2 2/3] PCI: Allow ATS to be always on for pre-CXL devices Nicolin Chen
2026-02-23 22:52 ` [PATCH v2 3/3] iommu/arm-smmu-v3: Allow ATS to be always on Nicolin Chen
2026-02-24 12:06 ` Jonathan Cameron
2026-02-24 14:51 ` Jason Gunthorpe
2026-02-24 15:57 ` Jonathan Cameron
2026-02-24 16:09 ` Jason Gunthorpe [this message]
2026-03-02 14:54 ` Jonathan Cameron
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