On Fri, Jul 01, 2022 at 02:44:51PM -0700, Nicolin Chen wrote: > 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 from the IOMMU driver during attach that the > reason attached failed is because of domain incompatability. EMEDIUMTYPE > is chosen because it is never used within the iommu subsystem today and > evokes a sense that the 'medium' aka the domain is incompatible. > > 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 all drivers to return EMEDIUMTYPE in their failure paths that are > related to domain incompatability. Also remove adjacent error prints for > these soft failures, to prevent a kernel log spam, since -EMEDIUMTYPE is > clear enough to indicate an incompatability error. > > Add kdocs describing this behavior. > > Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx> > Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx> > Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> > Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx> > --- > 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 +-- > 13 files changed, 47 insertions(+), 46 deletions(-) Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Jason
