From: Jason Gunthorpe <jgg@nvidia.com>
To: Yi Liu <yi.l.liu@intel.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
Lu Baolu <baolu.lu@linux.intel.com>,
Bjorn Helgaas <bhelgaas@google.com>,
David Woodhouse <dwmw2@infradead.org>,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
Joerg Roedel <joro@8bytes.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
Will Deacon <will@kernel.org>,
"patches@lists.linux.dev" <patches@lists.linux.dev>
Subject: Re: [PATCH] iommu: Allow ATS to work on VFs when the PF uses IDENTITY
Date: Mon, 12 Aug 2024 08:35:55 -0300 [thread overview]
Message-ID: <20240812113555.GP8378@nvidia.com> (raw)
In-Reply-To: <880c1858-afee-4c30-aac5-5da2925aaf11@intel.com>
On Mon, Aug 12, 2024 at 05:03:37PM +0800, Yi Liu wrote:
> > The PASID may require ATS to be enabled (ie SVA), but the RID may be
> > IDENTITY for performance. The poor device has no idea it is not
> > allowed to use ATS on the RID side :(
>
> If this is the only problematic case, the intel iommu driver in this
> patch could check the scalable mode before enabling ATS in the
> probe_device() op. In this way, the legacy mode iommu would keep the old
> ATS enable policy.
At some point we will need to address this.. At least when we add
PASID support to mlx5 it will need something since mlx5 is using ATS
on the RID right now.
Supporting ATS with the IDENTITY optimization is a good idea in the
IOMMU HW. The HW just has to answer the ATS with a 1:1 TA.
Next, telling the driver that ATS is enabled but doesn't work on the
RID would allow the driver to deal with it
Finally, doing things like using IDENTITY through a paging domain
would be a last resort for troubled devices.
Jason
next prev parent reply other threads:[~2024-08-12 11:37 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-07 18:19 [PATCH] iommu: Allow ATS to work on VFs when the PF uses IDENTITY Jason Gunthorpe
2024-08-09 2:36 ` Tian, Kevin
2024-08-09 13:28 ` Jason Gunthorpe
2024-08-12 0:09 ` Tian, Kevin
2024-08-12 9:03 ` Yi Liu
2024-08-12 11:35 ` Jason Gunthorpe [this message]
2024-08-13 3:00 ` Yi Liu
2024-08-09 19:10 ` Bjorn Helgaas
2024-08-12 2:20 ` Baolu Lu
2024-08-13 3:11 ` Yi Liu
2024-08-13 12:30 ` Jason Gunthorpe
2024-08-13 23:21 ` Yi Liu
2024-08-13 8:52 ` Joerg Roedel
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