[Bug 209025] The "VFIO_MAP_DMA failed: Cannot allocate memory" bug is back

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=209025

Niklas Schnelle (niklas@komani.de) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |axboe@kernel.dk,
                   |                            |niklas@komani.de

--- Comment #5 from Niklas Schnelle (niklas@komani.de) ---
Hi,

it's me Niklas from the KVM mailinglist discussion and yes
this is a very old pre-IBM, pre any work, Bugzilla account :D

I too did a bisect yesterday and also
encountered a few commits that had KVM in a very weird state
where not even the UEFI in the VM would boot, funnily enough
a BIOS based FreeBSD VM did still boot.

Anyway my bisect was successful and reverting the found
commit makes things work even on v5.9-rc2.

That said it is quite a strange result but I guess it makes
sense as that also deals with locked/pinned memory.
I'm assuming this might use the same accounting mechanism?

f74441e6311a28f0ee89b9c8e296a33730f812fc is the first bad commit
commit f74441e6311a28f0ee89b9c8e296a33730f812fc
Author: Jens Axboe <axboe@kernel.dk>
Date:   Wed Aug 5 13:00:44 2020 -0600

    io_uring: account locked memory before potential error case

    The tear down path will always unaccount the memory, so ensure that we
    have accounted it before hitting any of them.

    Reported-by: Tomáš Chaloupka <chalucha@gmail.com>
    Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
    Signed-off-by: Jens Axboe <axboe@kernel.dk>

 fs/io_uring.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

I've added Jens to the Bugzilla CC list not sure if he'll see
that though.

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