[PATCH v2 00/13] iommu: Define EINVAL as device/domain incompatibility

[PATCH v2 00/13] iommu: Define EINVAL as device/domain incompatibility

[Nicolin Chen]

This series is to replace the previous EMEDIUMTYPE patch in a VFIO series:
https://lore.kernel.org/kvm/Yxnt9uQTmbqul5lf@8bytes.org/

The purpose is to regulate all existing ->attach_dev callback functions to
use EINVAL exclusively for an incompatibility error between a device and a
domain. This allows VFIO and IOMMUFD to detect such a soft error, and then
try a different domain with the same device.

Among all the patches, the first two are preparatory changes. And then one
patch to update kdocs and the rest of them are per-driver changes.

Although it might be ideal to merge the previous VFIO series together with
this series, given the number of new changes, the review in the IOMMU list
might need a couple of rounds to finalize. Also, considering that v6.0 is
at rc5 now, perhaps we could merge this IOMMU series and the VFIO one in
different cycles to avoid merge conflicts. If there's less concern for it,
I can respin the finalized version with VFIO to merge into the VFIO tree.

This series is also available on Github:
https://github.com/nicolinc/iommufd/commits/iommu_attach_dev-v2

Changelog
v2:
 * Fixed kdocs format
 * Grouped with the virtio patch from Jean (with a small change)
 * Separated previous ENODEV and EINVAL changes to per-driver ones
 * Redone some of the changes to have explicit return values in the
   ->attach_dev() callback functions or their direct sub-functions.
v1: https://lore.kernel.org/linux-iommu/20220913082448.31120-1-nicolinc@nvidia.com/

Thanks!

Jean-Philippe Brucker (1):
  iommu/virtio: Constrain return value of ->attach_dev()

Nicolin Chen (12):
  iommu/msm: Add missing __disable_clocks calls
  iommu/amd: Drop unnecessary checks in amd_iommu_attach_device()
  iommu: Add return value rules to attach_dev op
  iommu/arm: Constrain return value of ->attach_dev()
  iommu/fsl: Constrain return value of ->attach_dev()
  iommu/intel: Constrain return value of ->attach_dev()
  iommu/ipmmu-vmsa: Constrain return value of ->attach_dev()
  iommu/mtk: Constrain return value of ->attach_dev()
  iommu/omap: Constrain return value of ->attach_dev()
  iommu/rockchip: Constrain return value of ->attach_dev()
  iommu/sprd: Constrain return value of ->attach_dev()
  iommu/tegra: Constrain return value of ->attach_dev()

 drivers/iommu/amd/iommu.c                   | 12 ++----------
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 13 ++-----------
 drivers/iommu/arm/arm-smmu/arm-smmu.c       |  7 ++-----
 drivers/iommu/arm/arm-smmu/qcom_iommu.c     |  9 ++-------
 drivers/iommu/fsl_pamu_domain.c             | 12 ++++++++----
 drivers/iommu/intel/iommu.c                 | 17 +++++++++--------
 drivers/iommu/ipmmu-vmsa.c                  | 10 +++++-----
 drivers/iommu/msm_iommu.c                   |  2 ++
 drivers/iommu/mtk_iommu.c                   |  9 +++++++--
 drivers/iommu/omap-iommu.c                  |  7 ++++---
 drivers/iommu/rockchip-iommu.c              |  4 +++-
 drivers/iommu/sprd-iommu.c                  |  4 +---
 drivers/iommu/tegra-gart.c                  |  2 +-
 drivers/iommu/tegra-smmu.c                  |  6 ++++--
 drivers/iommu/virtio-iommu.c                | 13 ++++++-------
 include/linux/iommu.h                       | 11 +++++++++++
 16 files changed, 69 insertions(+), 69 deletions(-)

-- 
2.17.1


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[PATCH v2 03/13] iommu: Add return value rules to attach_dev op

[Nicolin Chen]

Cases like VFIO wish to attach a device to an existing domain that was
not allocated specifically from the device. This raises a condition
where the IOMMU driver can fail the domain attach because the domain and
device are incompatible with each other.

This is a soft failure that can be resolved by using a different domain.

Provide a dedicated errno EINVAL from the IOMMU driver during attach that
the reason attached failed is because of domain incompatability.

VFIO can use this to know attach is a soft failure and it should continue
searching. Otherwise the attach will be a hard failure and VFIO will
return the code to userspace.

Update kdocs first to add rules of return value to the attach_dev op.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
 include/linux/iommu.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index ea30f00dc145..aacf9a2b151f 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -266,6 +266,17 @@ struct iommu_ops {
 /**
  * struct iommu_domain_ops - domain specific operations
  * @attach_dev: attach an iommu domain to a device
+ *  Return:
+ * * 0		- success
+ * * EINVAL	- exclusively, device and domain are incompatible. Must avoid
+ *		  kernel prints along with this errno. Any EINVAL returned from
+ *		  a kAPI must be converted to ENODEV if it is device-specific,
+ *		  or to some other reasonable errno being listed below
+ * * ENOMEM	- out of memory
+ * * ENOSPC	- no space left on device
+ * * EBUSY	- device is attached to a domain and cannot be changed
+ * * ENODEV	- device specific errors, not able to be attached
+ * * <others>	- treated as ENODEV by the caller. Use is discouraged
  * @detach_dev: detach an iommu domain from a device
  * @map: map a physically contiguous memory region to an iommu domain
  * @map_pages: map a physically contiguous set of pages of the same size to
-- 
2.17.1


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Re: [PATCH v2 00/13] iommu: Define EINVAL as device/domain incompatibility

[Nicolin Chen]

Hi all,

On Tue, Sep 13, 2022 at 10:12:33PM -0700, Nicolin Chen wrote:
 
> This series is also available on Github:
> https://github.com/nicolinc/iommufd/commits/iommu_attach_dev-v2
> 
> Changelog
> v2:

I just realized that the chain of this version is broken. Yet, I
think that people can still review the changes, though they may
not be grouped together. I will fix this in the next respin.

Thanks
Nicolin

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