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Re: [Xen-devel] pv-on-hvm kexec, howto reregister timer interrupt

To: Keir Fraser <keir.xen@xxxxxxxxx>
Subject: Re: [Xen-devel] pv-on-hvm kexec, howto reregister timer interrupt
From: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
Date: Sat, 23 Jul 2011 09:01:45 +0100
Cc: Olaf Hering <olaf@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On Sat, 2011-07-23 at 07:57 +0100, Keir Fraser wrote:
> On 22/07/2011 19:49, "Olaf Hering" <olaf@xxxxxxxxx> wrote:
> > What is the best way to reregister the timer interrupt in the kexec
> > kernel in a pv-on-hvm guest? Right now the crash shown below happens
> > because EVTCHNOP_bind_virq returns -EEXIST. Can the timer on the cpus be
> > unregistered during shutdown? xen_teardown_timer() does not allow that
> > for cpu #0.  I added some silly loop which tries to match vcpu/cpu in
> > bind_virq_to_irq() using EVTCHNOP_status to find the currently used port
> > number. This helps and booting proceeds, but I feel that cant be the
> > right approach.
> Sounbds like it's simply some Linux-guest issue here to be untangled. All
> Xen requires you to do is EVTCHNOP_close the old virq-evtchn binding.

That might be tricky to do in the target kernel, which may not know what
needs closing. There's EVTCHNOP_reset which looks like it would be a
sensible thing to call early on in the target but seems like it would
close to much -- e.g. the xenstore evtchn?


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