Re: [PATCH v5 0/5] cover-letter: Simplify vfio_iommu_type1 attach/detach routine

Alex Williamson
2022-07-06T17:42:35Z

On Fri, 1 Jul 2022 14:44:50 -0700
Nicolin Chen <nicolinc@nvidia.com> wrote:

> This is a preparatory series for IOMMUFD v2 patches. It enforces error
> code -EMEDIUMTYPE in iommu_attach_device() and iommu_attach_group() when
> an IOMMU domain and a device/group are incompatible. It also drops the
> useless domain->ops check since it won't fail in current environment.
>
> These allow VFIO iommu code to simplify its group attachment routine, by
> avoiding the extra IOMMU domain allocations and attach/detach sequences
> of the old code.
>
> Worths mentioning the exact match for enforce_cache_coherency is removed
> with this series, since there's very less value in doing that as KVM will
> not be able to take advantage of it -- this just wastes domain memory.
> Instead, we rely on Intel IOMMU driver taking care of that internally.
>
> This is on github:
> https://github.com/nicolinc/iommufd/commits/vfio_iommu_attach

How do you foresee this going in, I'm imagining Joerg would merge the
first patch via the IOMMU tree and provide a topic branch that I'd
merge into the vfio tree along with the remaining patches. Sound
right? Thanks,

Alex

> Changelog
> v5:
> * Rebased on top of Robin's "Simplify bus_type determination".
> * Fixed a wrong change returning -EMEDIUMTYPE in arm-smmu driver.
> * Added Baolu's "Reviewed-by".
> v4:
> * Dropped -EMEDIUMTYPE change in mtk_v1 driver per Robin's input
> * Added Baolu's and Kevin's Reviewed-by lines
> v3: https://lore.kernel.org/kvm/20220623200029.26007-1-nicolinc@nvidia.com/
> * Dropped all dev_err since -EMEDIUMTYPE clearly indicates what error.
> * Updated commit message of enforce_cache_coherency removing patch.
> * Updated commit message of domain->ops removing patch.
> * Replaced "goto out_unlock" with simply mutex_unlock() and return.
> * Added a line of comments for -EMEDIUMTYPE return check.
> * Moved iommu_get_msi_cookie() into alloc_attach_domain() as a cookie
> should be logically tied to the lifetime of a domain itself.
> * Added Kevin's "Reviewed-by".
> v2: https://lore.kernel.org/kvm/20220616000304.23890-1-nicolinc@nvidia.com/
> * Added -EMEDIUMTYPE to more IOMMU drivers that fit the category.
> * Changed dev_err to dev_dbg for -EMEDIUMTYPE to avoid kernel log spam.
> * Dropped iommu_ops patch, and removed domain->ops in VFIO directly,
> since there's no mixed-driver use case that would fail the sanity.
> * Updated commit log of the patch removing enforce_cache_coherency.
> * Fixed a misplace of "num_non_pinned_groups--" in detach_group patch.
> * Moved "num_non_pinned_groups++" in PATCH-5 to the common path between
> domain-reusing and new-domain pathways, like the code previously did.
> * Fixed a typo in EMEDIUMTYPE patch.
> v1: https://lore.kernel.org/kvm/20220606061927.26049-1-nicolinc@nvidia.com/
>
> Jason Gunthorpe (1):
> vfio/iommu_type1: Prefer to reuse domains vs match enforced cache
> coherency
>
> Nicolin Chen (4):
> iommu: Return -EMEDIUMTYPE for incompatible domain and device/group
> vfio/iommu_type1: Remove the domain->ops comparison
> vfio/iommu_type1: Clean up update_dirty_scope in detach_group()
> vfio/iommu_type1: Simplify group attachment
>
> drivers/iommu/amd/iommu.c | 2 +-
> drivers/iommu/apple-dart.c | 4 +-
> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 15 +-
> drivers/iommu/arm/arm-smmu/arm-smmu.c | 5 +-
> drivers/iommu/arm/arm-smmu/qcom_iommu.c | 9 +-
> drivers/iommu/intel/iommu.c | 10 +-
> drivers/iommu/iommu.c | 28 ++
> drivers/iommu/ipmmu-vmsa.c | 4 +-
> drivers/iommu/omap-iommu.c | 3 +-
> drivers/iommu/s390-iommu.c | 2 +-
> drivers/iommu/sprd-iommu.c | 6 +-
> drivers/iommu/tegra-gart.c | 2 +-
> drivers/iommu/virtio-iommu.c | 3 +-
> drivers/vfio/vfio_iommu_type1.c | 352 ++++++++++----------
> 14 files changed, 229 insertions(+), 216 deletions(-)
>