From: Jason Gunthorpe <jgg@ziepe.ca>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Samiullah Khawaja <skhawaja@google.com>,
Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
Kevin Tian <kevin.tian@intel.com>,
Alex Williamson <alex@shazbot.org>,
iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Pasha Tatashin <pasha.tatashin@soleen.com>,
David Matlack <dmatlack@google.com>,
Lu Baolu <baolu.lu@linux.intel.com>,
Pranjal Shrivastava <praan@google.com>
Subject: Re: [RFC PATCH 3/3] iommu/arm-smmu-v3: Add support for hitless replace of S1 domains
Date: Fri, 23 Oct 2026 10:49:00 -0300 [thread overview]
Message-ID: <20261023134900.GB3977851@ziepe.ca> (raw)
In-Reply-To: <3d1eb92f-3447-49f0-a210-fd4fa015304b@arm.com>
On Fri, Oct 23, 2026 at 02:43:28PM +0100, Robin Murphy wrote:
> > @@ -3664,8 +3726,8 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev,
> > struct arm_smmu_cd target_cd;
> > arm_smmu_make_s1_cd(&target_cd, master, smmu_domain);
> > - arm_smmu_write_cd_entry(master, IOMMU_NO_PASID, cdptr,
> > - &target_cd);
> > + arm_smmu_replace_cd_entry(master, IOMMU_NO_PASID, cdptr,
> > + &target_cd);
>
> No, we cannot blindly do this for arbitrary ->attach_dev calls - the
> majority of S1->S1 transitions are going to be moving back and forth between
> the default domain and user domains, where there is zero expectation, let
> alone guarantee, that the translations would be equivalent and thus not
> liable to lead to TLB conflict aborts or amalgamation hell.
Heh, yeah this probably only works properly with BBML2 or something so
the temporary ASID doesn't explode.
Jason
next prev parent reply other threads:[~2026-10-23 13:49 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-25 1:13 [RFC PATCH 0/3] iommu/arm-smmu-v3: Add support for hitless replace of CD entries Samiullah Khawaja
2026-09-25 1:13 ` [RFC PATCH 1/3] vfio: selftests: Add support of creating iommus from iommufd Samiullah Khawaja
2026-10-21 22:19 ` David Matlack
2026-10-23 23:04 ` Samiullah Khawaja
2026-09-25 1:13 ` [RFC PATCH 2/3] vfio: selftests: Add iommufd hwpt replace test Samiullah Khawaja
2026-10-21 22:39 ` David Matlack
2026-10-23 23:10 ` Samiullah Khawaja
2026-09-25 1:13 ` [RFC PATCH 3/3] iommu/arm-smmu-v3: Add support for hitless replace of S1 domains Samiullah Khawaja
2026-10-23 13:43 ` Robin Murphy
2026-10-23 13:49 ` Jason Gunthorpe [this message]
2026-10-23 14:04 ` Robin Murphy
2026-10-23 14:29 ` Jason Gunthorpe
2026-10-23 23:31 ` Samiullah Khawaja
2026-09-25 21:44 ` [RFC PATCH 0/3] iommu/arm-smmu-v3: Add support for hitless replace of CD entries David Matlack
2026-09-25 22:27 ` Samiullah Khawaja
2026-10-23 12:10 ` Robin Murphy
2026-10-23 13:46 ` Jason Gunthorpe
2026-10-23 14:12 ` Robin Murphy
2026-10-23 22:59 ` Samiullah Khawaja
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