Re: [PATCHv3 2/2] x86/selftests: Add test for mapping placement for 5-level paging

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> writes:

> With 5-level paging, we have 56-bit virtual address space available for
> userspace. But we don't want to expose userspace to addresses above
> 47-bits, unless it asked specifically for it.
>
> We use mmap(2) hint address as a way for kernel to know if it's okay to
> allocate virtual memory above 47-bit.
>
> Let's add a self-test that covers few corner cases of the interface.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

Can we move this to selftest/vm/ ? I had a variant which i was using to
test issues on ppc64. One change we did recently was to use >=128TB as
the hint addr value to select larger address space. I also would like to
check for exact mmap return addr in some case. Attaching below the test
i was using. I will check whether this patch can be updated to test what
is converted in my selftest. I also want to do the boundary check twice.
The hash trasnslation mode in POWER require us to track addr limit and
we had bugs around address space slection before and after updating the
addr limit.