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
