From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753296AbbGNPo5 (ORCPT <rfc822;w@1wt.eu>);
	Tue, 14 Jul 2015 11:44:57 -0400
Received: from www.linutronix.de ([62.245.132.108]:32888 "EHLO
	Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1752232AbbGNPo4 (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 14 Jul 2015 11:44:56 -0400
Date: Tue, 14 Jul 2015 17:44:42 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>
cc: LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, Peter Anvin <hpa@zytor.com>,
        xiao jin <jin.xiao@intel.com>, Joerg Roedel <jroedel@suse.de>,
        Borislav Petkov <bp@suse.de>,
        Yanmin Zhang <yanmin_zhang@linux.intel.com>,
        xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [patch 1/4] hotplug: Prevent alloc/free of irq descriptors during
 cpu up/down
In-Reply-To: <55A51F10.7010407@oracle.com>
Message-ID: <alpine.DEB.2.11.1507141743150.18576@nanos>
References: <20150705170530.849428850@linutronix.de> <20150705171102.063519515@linutronix.de> <55A51F10.7010407@oracle.com>
User-Agent: Alpine 2.11 (DEB 23 2013-08-11)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
X-Linutronix-Spam-Score: -1.0
X-Linutronix-Spam-Level: -
X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required,  ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.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