[Xen-devel] Re: [PATCH][VNC Auth] Fix qemu-dm becomes defunct when rebooting hvm domain

[Masami Watanabe <masami.watanabe@xxxxxxxxxxxxxx>]

Hi all,

I am sorry for the delayed response.

On Fri, 27 Oct 2006 17:39:42 +0100, Daniel P. Berrange wrote:
> Not sure why qemu would do defunct though - if the vncpasswd is not set
> in xenstore, it ought to have just fallen back to no-password auth.

Yes. Thanks Dan.


On Fri, Oct 27, 2006 at 05:16:57PM +0100, Keir Fraser wrote:
> That would mean that you¹d fall back to the default VNC password though,
> right? Why would it cause qemu to fail to restart and become a defunct
> process?

Thanks Keir, for your correction.
Please refer to the following for accurate processing.
- When qemu-dm start, qemu-dm is sure to need vncpasswd in xenstore.
      main()@vl.c -> xenstore_read_vncpasswd()@xenstore.c
  Null string vncpasswd is allowed. but non  vncpasswd is not allowed.
- If config.remove() in image.py, vncpasswd is not preserved in xend.
  When rebooting guest domain, xend cannot pass qemu-dm vncpasswd.
- When vncpasswd cannot be read from xenstore, qemu-dm is exit(1).
  As a result, qemu-dm becomes defunct process.

Best regards,
Masami



On Fri, 27 Oct 2006 17:39:42 +0100, Daniel P. Berrange wrote:
> On Fri, Oct 27, 2006 at 05:16:57PM +0100, Keir Fraser wrote:
> > On 25/10/06 11:07 pm, "Masami Watanabe" <masami.watanabe@xxxxxxxxxxxxxx>
> > wrote:
> >
> > > Sorry, I should not have removed infomation on xend.
> > >
> > >   image.py, line 399, in configVNC
> > >     config.remove(['vncpasswd', vncpasswd_vmconfig])
> > >
> > > When vncpasswd is removed, qemu-dm cannot be started in reboot of hvm 
> > > domain.
> > > Because necessary information disappears.
> > > It cannot be helped though information in config list remains in xenstore.
> > >
> > > This patch corrects above.
> >
> > That would mean that you¹d fall back to the default VNC password though,
> > right? Why would it cause qemu to fail to restart and become a defunct
> > process?
>
> No, it looks correct to me - we were scrubbing the vncpassword from the
> guest config after using it, so that it didn't appear in the SXPR data
> with doing 'xm list --long' etc. But turns out we do need the password
> later on after all, so we can't scrub it completely. Perhaps we just need
> to scrub it out on the fly when talking to XM & other apps instead - i've
> already been working on a patch to scrub it out when loggin the guest
> data to /var/log/xen/xend.log.
>
> This 'config.remove' thing also impacted my equivalent vncpassword patches
> for the paravirt framebuffer, because it meant when you do a save/restore
> or a migrate, and started the VNC daemon it no longer found a password.
>
> Not sure why qemu would do defunct though - if the vncpasswd is not set
> in xenstore, it ought to have just fallen back to no-password auth.
>
> Dan.
> --
> |=- Red Hat, Engineering, Emerging Technologies, Boston.  +1 978 392 2496 -=|
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