From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: [PATCH][RFC] pv-ops: fix shared irq device	passthrough
Date: Tue, 10 Nov 2009 10:44:59 -0800
Message-ID: <4AF9B4AB.9060302@goop.org>
References: <715D42877B251141A38726ABF5CABF2C05509A75F3@pdsmsx503.ccr.corp.intel.com>
	<4AE60646.7050307@goop.org>
	<715D42877B251141A38726ABF5CABF2C05509A7C3A@pdsmsx503.ccr.corp.intel.com>
	<4AEA1D82.8060609@goop.org>
	<715D42877B251141A38726ABF5CABF2C0550A02DAD@pdsmsx503.ccr.corp.intel.com>
	<4AEB5BF9.20307@goop.org>
	<715D42877B251141A38726ABF5CABF2C055064A406@pdsmsx503.ccr.corp.intel.com>
	<715D42877B251141A38726ABF5CABF2C0550A64B6C@pdsmsx503.ccr.corp.intel.com>
	<715D42877B251141A38726ABF5CABF2C05534DC58B@pdsmsx503.ccr.corp.intel.com>
	<20091110163058.GB23000@phenom.dumpdata.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xensource.com>
In-Reply-To: <20091110163058.GB23000@phenom.dumpdata.com>
List-Unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xensource.com>
List-Help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-Subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
Sender: xen-devel-bounces@lists.xensource.com
Errors-To: xen-devel-bounces@lists.xensource.com
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: "Kay, Allen M" <allen.m.kay@intel.com>, "'xen-devel@lists.xensource.com'" <xen-devel@lists.xensource.com>, "Han, Weidong" <weidong.han@intel.com>, "'keir.fraser@eu.citrix.com'" <keir.fraser@eu.citrix.com>
List-Id: xen-devel@lists.xenproject.org

On 11/10/09 08:30, Konrad Rzeszutek Wilk wrote:
> With this patch you can share the PCI devices on the same IRQ, correct? Will
> this mean that you can assign to a guest a USB controller, while
> Dom0 has controller of the PCI NIC (and assuming that both of those
> share the same interrupt line)? If so, won't the Dom0 start throwing
> a fit b/c there are unhandled IRQs and eventually disable the IRQ line?
>
>
> Or even the guest decide that there are too many IRQs and decided to
> disable the IRQ line?
>   

It would be easy to add a dummy handler which always returns IRQ_HANDLED
for every cross-domain shared interrupt to prevent this.  Of course that
would paper over any real spurious/screaming interrupt problem, but we
could add some extra logic into the dummy handler if necessary.

I merged the patch, and had to add the new parameter to
xen_allocate_pirq() in arch/x86/pci/xen.c.  I just made it 0 which
should have no functional difference from before, but I'll leave it to
you to decide what it really should be.

    J