On 2022/7/1 04:36, 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> Signed-off-by: Nicolin Chen<nicolinc@xxxxxxxxxx>
Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> Best regards, baolu
