On Wed, Aug 09, 2023 at 09:30:12AM +0000, Liu, Yi L wrote:
Yeah, adding new structures to ucmd_buffer may increase the size as well if the new one is larger. While for an array, if there is new entry, it is for sure to increase the size. I remember there is one tricky thing when handling the selftest type. E.g. it is defined as 0xbadbeef, if using it to index array, it would expire. So we have some special handling on it. If defining the things in iommu_ops, it is simpler. Selftest may be not so critical to determining the direction though.
Maybe we are trying too hard to make it "easy" on the driver.
Can't we just have the driver invoke some:
driver_iommufd_invalidate_op(??? *opaque) { struct driver_base_struct args;
rc = iommufd_get_args(opaque, &args, sizeof(args), offsetof(args, last)); if (rc) return rc; }
The whole point of this excercise was to avoid the mistake where drivers code the uapi checks incorrectly. We can achieve the same outcome by providing a mandatory helper.
Similarly for managing the array of invalidation commands.
Jason