From: Jason Gunthorpe <jgg@nvidia.com>
To: "Tian, Kevin" <kevin.tian@intel.com>
Cc: Baolu Lu <baolu.lu@linux.intel.com>,
Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>,
Dmytro Maluka <dmaluka@chromium.org>,
Samiullah Khawaja <skhawaja@google.com>,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/3] iommu/vt-d: Use 128-bit atomic updates for context entries
Date: Fri, 16 Jan 2026 10:33:31 -0400 [thread overview]
Message-ID: <20260116143331.GJ961588@nvidia.com> (raw)
In-Reply-To: <BN9PR11MB527605C53AD9E8C6C6DCB2498C8DA@BN9PR11MB5276.namprd11.prod.outlook.com>
On Fri, Jan 16, 2026 at 05:19:52AM +0000, Tian, Kevin wrote:
> btw the way that VT-d spec describes it as "software MUST use
> 128bit..." highly suggest that it's either as AMD or with exception
> only on very early generations. Another exception is VM which
> may have hardware supporting 128bit but vcpu model doesn't,
> but I doubt it's a meaningful configuration nowadays...
The VMs is an interesting point..
I think with a bit of fiddling the entry_set mechanism could fall back
to 64 bit operation automatically, and that would handle the
compatability needs. It would be much less hitless in such systems but
who cares?
Jason
next prev parent reply other threads:[~2026-01-16 14:33 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-13 3:00 [PATCH 0/3] iommu/vt-d: Ensure atomicity in context and PASID entry updates Lu Baolu
2026-01-13 3:00 ` [PATCH 1/3] iommu/vt-d: Use 128-bit atomic updates for context entries Lu Baolu
2026-01-13 19:27 ` Dmytro Maluka
2026-01-14 5:14 ` Baolu Lu
2026-01-14 10:55 ` Dmytro Maluka
2026-01-15 2:26 ` Baolu Lu
2026-01-15 13:12 ` Jason Gunthorpe
2026-01-14 7:54 ` Tian, Kevin
2026-01-15 3:26 ` Baolu Lu
2026-01-15 5:59 ` Tian, Kevin
2026-01-15 13:23 ` Jason Gunthorpe
2026-01-16 5:19 ` Tian, Kevin
2026-01-16 14:33 ` Jason Gunthorpe [this message]
2026-01-13 3:00 ` [PATCH 2/3] iommu/vt-d: Clear Present bit before tearing down PASID entry Lu Baolu
2026-01-13 19:34 ` Dmytro Maluka
2026-01-14 5:38 ` Baolu Lu
2026-01-14 11:12 ` Dmytro Maluka
2026-01-15 2:45 ` Baolu Lu
2026-01-15 21:35 ` Dmytro Maluka
2026-01-16 6:06 ` Baolu Lu
2026-01-20 13:49 ` Dmytro Maluka
2026-01-14 7:32 ` Tian, Kevin
2026-01-14 8:27 ` Baolu Lu
2026-01-15 5:49 ` Tian, Kevin
2026-01-13 3:00 ` [PATCH 3/3] iommu/vt-d: Rework hitless PASID entry replacement Lu Baolu
2026-01-13 15:05 ` Jason Gunthorpe
2026-01-14 6:03 ` Baolu Lu
2026-01-13 19:27 ` Samiullah Khawaja
2026-01-13 20:56 ` Jason Gunthorpe
2026-01-14 5:45 ` Baolu Lu
2026-01-14 7:26 ` Tian, Kevin
2026-01-14 13:17 ` Jason Gunthorpe
2026-01-14 18:51 ` Samiullah Khawaja
2026-01-14 19:07 ` Jason Gunthorpe
2026-01-15 5:44 ` Tian, Kevin
2026-01-15 13:28 ` Jason Gunthorpe
2026-01-16 6:16 ` Tian, Kevin
2026-01-13 19:39 ` Dmytro Maluka
2026-01-13 20:06 ` Dmytro Maluka
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