> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Thursday, August 22, 2024 10:46 PM
>
> This results in passing 0 or just IOMMU_CACHE to iommu_map(). Most of
> the page table formats don't like this:
>
> amdv1 - -EINVAL
> armv7s - returns 0, doesn't update mapped
> arm-lpae - returns 0 doesn't update mapped
> dart - returns 0, doesn't update mapped
> VT-D - returns -EINVAL
>
> Unfortunately the three formats that return 0 cause serious problems:
>
> - Returning ret = but not uppdating mapped from domain->map_pages()
> causes an infinite loop in __iommu_map()
>
> - Not writing ioptes means that VFIO/iommufd have no way to recover them
> and we will have memory leaks and worse during unmap
>
> Since almost nothing can support this, and it is a useless thing to do,
> block it early in iommufd.
>
> Cc: stable@xxxxxxxxxx
> Fixes: aad37e71d5c4 ("iommufd: IOCTLs for the io_pagetable")
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
