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 S1754775AbcBXO6o (ORCPT <rfc822;w@1wt.eu>);
	Wed, 24 Feb 2016 09:58:44 -0500
Received: from smtp02.citrix.com ([66.165.176.63]:7067 "EHLO SMTP02.CITRIX.COM"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1754040AbcBXO6n (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Wed, 24 Feb 2016 09:58:43 -0500
X-IronPort-AV: E=Sophos;i="5.22,494,1449532800"; 
   d="scan'208";a="340752593"
Subject: Re: [Xen-devel] [PATCH] xen/x86: Zero out .bss for PV guests
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Andrew Cooper <andrew.cooper3@citrix.com>, <konrad.wilk@oracle.com>
References: <1456178767-8038-1-git-send-email-boris.ostrovsky@oracle.com>
 <56CDBA5A.1000600@citrix.com> <56CDBB0F.9000203@citrix.com>
 <56CDC39B.3060004@oracle.com>
CC: <xen-devel@lists.xenproject.org>, <mcgrof@kernel.org>,
        <linux-kernel@vger.kernel.org>
From: David Vrabel <david.vrabel@citrix.com>
Message-ID: <56CDC520.1000609@citrix.com>
Date: Wed, 24 Feb 2016 14:58:40 +0000
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101
 Icedove/38.5.0
MIME-Version: 1.0
In-Reply-To: <56CDC39B.3060004@oracle.com>
Content-Type: text/plain; charset="windows-1252"
Content-Transfer-Encoding: 7bit
X-DLP: MIA1
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 24/02/16 14:52, Boris Ostrovsky wrote:
> On 02/24/2016 09:15 AM, Andrew Cooper wrote:
>> On 24/02/16 14:12, David Vrabel wrote:
>>> On 22/02/16 22:06, Boris Ostrovsky wrote:
>>>> Baremetal kernels clear .bss early in the boot. Since Xen PV guests
>>>> don't
>>>> excecute that early code they should do it too.
>>>>
>>>> (Since we introduce macros for specifying 32- and 64-bit registers we
>>>> can get rid of ifdefs in startup_xen())
>>> .bss must have been cleared for PV guests otherwise they would be
>>> horribly broken.  What was the method and why is it no longer
>>> sufficient?
> 
> I couldn't find this being done anywhere, hence this patch.
> 
>> The domain builder hands out zeroed pages.  I don't believe we guarantee
>> that the guests RAM is clean, but it is in practice.
> 
> OK, that's what I suspected but didn't actually look.
> 
> I, in fact, wonder whether this should go to stable trees as well.

Yes.  Can you respin with a commit message explaining?  (Or just provide
the message here and I'll fix it up).

David