Re: [Qemu-devel] [Qemu-stable] Recent patches for 2.4

[Peter Lieven <pl@kamp.de>]

Am 31.07.2015 um 11:29 schrieb Paolo Bonzini:
>
> On 31/07/2015 10:35, Peter Lieven wrote:
>> Am 31.07.2015 um 10:22 schrieb Paolo Bonzini:
>>>> 52c91da memory: do not add a reference to the owner of aliased regions
>>> This could be backported, yes.  Feel free to send it to qemu-stable.
>>> However, the bug was only visible with virtio 1.
>> Applies cleanly to 2.3.1-staging.
> Good.
>
>>>> edec47c main-loop: fix qemu_notify_event for aio_notify optimization
>>> Part of the above AioContext series.
>> So either the whole series or none of them I guess?
> It's a separate bug, and theoretically it's there in 2.3.1 as well, but
> no one ever reproduced it (it would hang in make check) so not worthwhile.

I maybe found another case where this bugfix seems to help. For various
reasons I'm still on 2.2.1 stable with some CVE fixes manually applied.

I currently work on the problem that a haning NFS Server where I mount
my CDROM ISOs from takes down the whole vServer because the main loop
hangs sooner or later.

I already put some patches on the list which help to improve the situation:

ide/atapi: make PIO read requests async
block/io: allow AIOCB without callback
ide/atapi: partially avoid deadlock if the storage backend is dead
block/nfs: cache allocated filesize for read-only files

However, I ended up with one case where Qemu deadlocks in bdrv_drain_one.

Scenario:
  - Windows 2012R2 with a random ISO mounted.
  - Block communication to NFS via Firewall
  - execute 'eject ide1-cd0' in the HMP
  - restore connectivity.

The HMP hangs forever even if the NFS connectivity itself is restored.

Peter