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iommu/arm-smmu-v3: Mark EATS_TRANS safe when computing the update sequence

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[ Upstream commit 7cad800485 ]

If VM wants to toggle EATS_TRANS off at the same time as changing the CFG,
hypervisor will see EATS change to 0 and insert a V=0 breaking update into
the STE even though the VM did not ask for that.

In bare metal, EATS_TRANS is ignored by CFG=ABORT/BYPASS, which is why this
does not cause a problem until we have the nested case where CFG is always
a variation of S2 trans that does use EATS_TRANS.

Relax the rules for EATS_TRANS sequencing, we don't need it to be exact as
the enclosing code will always disable ATS at the PCI device when changing
EATS_TRANS. This ensures there are no ATS transactions that can race with
an EATS_TRANS change so we don't need to carefully sequence these bits.

Fixes: 1e8be08d1c ("iommu/arm-smmu-v3: Support IOMMU_DOMAIN_NESTED")
Cc: stable@vger.kernel.org
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Shuai Xue <xueshuai@linux.alibaba.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Jason Gunthorpe 2026-01-15 10:23:30 -08:00 • committed by Sasha Levin
commit 779e0c250a
1 changed files with 26 additions and 0 deletions
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