linux-kernel - Re: [Xen-devel] [PATCH 2/3] xen/pv-on-hvm kexec: rebind virqs to existing eventchannel ports

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Date:	Tue, 9 Aug 2011 11:29:38 +0200
From:	Olaf Hering <olaf@...fle.de>
To:	Ian Campbell <Ian.Campbell@...rix.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Konrad <konrad.wilk@...cle.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>
Subject: Re: [Xen-devel] [PATCH 2/3] xen/pv-on-hvm kexec: rebind virqs to
 existing eventchannel ports

On Tue, Aug 09, Ian Campbell wrote:

> On Thu, 2011-08-04 at 17:20 +0100, Olaf Hering wrote:
> > During a kexec boot some virqs such as timer and debugirq were already
> > registered by the old kernel.  The hypervisor will return -EEXISTS from
> > the new EVTCHNOP_bind_virq request and the BUG in bind_virq_to_irq()
> > triggers.  Catch the -EEXISTS error and loop through all possible ports to find
> > what port belongs to the virq/cpu combo.
> 
> Would it be better to proactively just query the status of all event
> channels early on, like you do in find_virq, and setup the irq info
> structures as appropriate? Rather than waiting for an -EEXISTS I mean.

Doing one hypercall in the common case is cheaper than doing a dozen in
the kexec case.

If you prefer I will rearrange this part and query first.

Olaf
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