]> git.proxmox.com Git - mirror_ubuntu-kernels.git/commit
iommu/arm-smmu: Report IOMMU_CAP_CACHE_COHERENCY even betterer
authorRobin Murphy <robin.murphy@arm.com>
Thu, 15 Dec 2022 16:51:55 +0000 (16:51 +0000)
committerJoerg Roedel <jroedel@suse.de>
Fri, 13 Jan 2023 12:46:20 +0000 (13:46 +0100)
commitac9c5e92dd15b9927e7355ccf79df76a58b44344
tree99db9b13caf5ab535d3128e9d8cfca2cee0c3ed9
parentb7bfaa761d760e72a969d116517eaa12e404c262
iommu/arm-smmu: Report IOMMU_CAP_CACHE_COHERENCY even betterer

Although it's vanishingly unlikely that anyone would integrate an SMMU
within a coherent interconnect without also making the pagetable walk
interface coherent, the same effect happens if a coherent SMMU fails to
advertise CTTW correctly. This turns out to be the case on some popular
NXP SoCs, where VFIO started failing the IOMMU_CAP_CACHE_COHERENCY test,
even though IOMMU_CACHE *was* previously achieving the desired effect
anyway thanks to the underlying integration.

While those SoCs stand to gain some more general benefits from a
firmware update to override CTTW correctly in DT/ACPI, it's also easy
to work around this in Linux as well, to avoid imposing too much on
affected users - since the upstream client devices *are* correctly
marked as coherent, we can trivially infer their coherent paths through
the SMMU as well.

Reported-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Fixes: df198b37e72c ("iommu/arm-smmu: Report IOMMU_CAP_CACHE_COHERENCY better")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/d6dc41952961e5c7b21acac08a8bf1eb0f69e124.1671123115.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
drivers/iommu/arm/arm-smmu/arm-smmu.c