From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [patch 1/4] hotplug: Prevent alloc/free of irq
 descriptors during cpu up/down
Date: Tue, 14 Jul 2015 17:44:42 +0200 (CEST)
Message-ID: <alpine.DEB.2.11.1507141743150.18576__23294.7368095212$1436888809$gmane$org@nanos>
References: <20150705170530.849428850@linutronix.de>
	<20150705171102.063519515@linutronix.de>
	<55A51F10.7010407@oracle.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
Received: from mail6.bemta3.messagelabs.com ([195.245.230.39])
	by lists.xen.org with esmtp (Exim 4.72)
	(envelope-from <tglx@linutronix.de>) id 1ZF2ON-0005KA-Hb
	for xen-devel@lists.xenproject.org; Tue, 14 Jul 2015 15:45:11 +0000
In-Reply-To: <55A51F10.7010407@oracle.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Yanmin Zhang <yanmin_zhang@linux.intel.com>, Joerg Roedel <jroedel@suse.de>, Peter Zijlstra <peterz@infradead.org>, LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@kernel.org>, Peter Anvin <hpa@zytor.com>, xen-devel <xen-devel@lists.xenproject.org>, Borislav Petkov <bp@suse.de>, xiao jin <jin.xiao@intel.com>
List-Id: xen-devel@lists.xenproject.org

On Tue, 14 Jul 2015, Boris Ostrovsky wrote:
> > Prevent allocation and freeing of interrupt descriptors accross cpu
> > hotplug.
> 
> 
> This breaks Xen guests that allocate interrupt descriptors in .cpu_up().

And where exactly does XEN allocate those descriptors?
 
> Any chance this locking can be moved into arch code?

No.

> (The patch doesn't appear to have any side effects for the down path since Xen
> guests deallocate descriptors in __cpu_die()).
 
Exact place please.

Thanks,

	tglx