[Hypervisor Live Update] Notes from February 24, 2025

[Pratyush Yadav]

Hi all,

On Sun, Mar 02 2025, David Rientjes wrote:

> Hi everybody,
>
> Here are the notes from the last Hypervisor Live Update call that happened 
> on Monday, February 24.  Thanks for everybody who was involved!
>
[...]
>
> Pratyush took the AI to look at implementation on memfd.  Mike took the
> AI to look at memory reservation.
>
> ----->o-----
> I pivoted the discussion toward fdbox which ended up never being posted
> upstream.  Pratyush provided the link to the most recent code:
> https://github.com/agraf/linux-2.6/blob/kvm-kho-gmem-test/drivers/misc/fdbox.c
> This work likely would need to be picked up to pursue upstream because
> the current code has several TODO's.  (A struct miscdevice was called out
> as curious.)
>
> It was noted that it would be difficult to support memfd without
> something like fdbox, so whether the fdbox code itself were upstreamed or
> it becomes more generic from the work on memfd, the base support would
> need to be provided somehow.
>
> Mike and Jason suggested designing fdbox and then starting to use it for
> memfd.  This would need to be aligned by stakeholders, including the UAPI
> for fdbox.  Pratyush will be looking into fdbox or inventing something
> similar while working on memfd.
>
> We need to propose the fdbox design and UAPI.

As promised, I have taken the last couple weeks in coming up with a
basic FDBox design, along with having memfd use it (currently via shmem,
since I am more familiar with that than with hugetlbfs). The patches can
be found at [0].

I am travelling next week so I am not sure if I will be able to attend
the next session. If I do, I would like to talk more about the patches
and FDBox if time permits. Anyway, looking forward to getting some
feedback on the patches :-)

[0] https://lore.kernel.org/linux-mm/20250307005830.65293-1-ptyadav@amazon.de/T/#u

[...]

-- 
Regards,
Pratyush Yadav