Re: [Xen-devel] [XEN PATCH for-4.13 v2 0/6] Fix: libxl workaround, multiple connection to single QMP socket

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

On 30/10/2019 19:06, Anthony PERARD wrote:
> Patch series available in this git branch:
> https://xenbits.xen.org/git-http/people/aperard/xen-unstable.git 
> br.fix-ev_qmp-multi-connect-v2
> 
> Hi,
> 
> QEMU's QMP socket doesn't allow multiple concurrent connection. Also, it
> listen() on the socket with a `backlog' of only 1. On Linux at least, once 
> that
> backlog is filled connect() will return EAGAIN if the socket fd is
> non-blocking. libxl may attempt many concurrent connect() attempt if for
> example a guest is started with several PCI passthrough devices, and a
> connect() failure lead to a failure to start the guest.
> 
> Since we can't change the listen()'s `backlog' that QEMU use, we need other
> ways to workaround the issue. This patch series introduce a lock to acquire
> before attempting to connect() to the QMP socket. Since the lock might be held
> for to long, the series also introduce a way to cancel the acquisition of the
> lock, this means killing the process that tries to get the lock.
> 
> See thread[1] for discussed alternative.
> [1] https://lists.xenproject.org/archives/html/xen-devel/2019-10/msg01815.html
> 
> Cheers,
> 
> Anthony PERARD (6):

Hi Anthony,

Re-tested, especially the pci-pt part, still works for me.
Thanks again (and thanks for providing a git branch)

--
Sander

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