From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH for-4.6] x86/gdt: Drop write-only,
 xalloc()'d array from set_gdt()
Date: Tue, 4 Aug 2015 15:05:54 +0100
Message-ID: <55C0C6C2.1040202@citrix.com>
References: <1438621543-21062-1-git-send-email-andrew.cooper3@citrix.com>
	<20150804093400.GW26074@zion.uk.xensource.com>
	<1438696761.31129.120.camel@citrix.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
In-Reply-To: <1438696761.31129.120.camel@citrix.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: Ian Campbell <ian.campbell@citrix.com>, Wei Liu <wei.liu2@citrix.com>, George Dunlap <george.dunlap@eu.citrix.com>
Cc: Tim Deegan <tim@xen.org>, Jan Beulich <JBeulich@suse.com>, Xen-devel <xen-devel@lists.xen.org>
List-Id: xen-devel@lists.xenproject.org

On 04/08/15 14:59, Ian Campbell wrote:
> On Tue, 2015-08-04 at 10:34 +0100, Wei Liu wrote:
>> On Mon, Aug 03, 2015 at 06:05:43PM +0100, Andrew Cooper wrote:
>>> It is not used, and can cause a spurious failure of the set_gdt() 
>>> hypercall in
>>> low memory situations.
>>>
>>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>>> ---
>>> CC: Jan Beulich <JBeulich@suse.com>
>>> ---
>> This array does appear to be write-only and never gets read.
>>
>> FWIW
>>
>> Reviewed-by: Wei Liu <wei.liu2@citrix.com>
> The use was removed by:
>
> commit 5889a3e1d123bdad4a3d150310d647db55459966
> Author: Tim Deegan <tim@xen.org>
> Date:   Thu May 17 10:24:54 2012 +0100
>
>     x86/mm: Use get_page_from_gfn() instead of get_gfn()/put_gfn.
>     
>     Signed-off-by: Tim Deegan <tim@xen.org>
>     Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
>
> after it was introduced by:
>
> commit 51032ca058e43fbd37ea1f7c7c003496f6451340
> Author: Andres Lagar-Cavilla <andres@lagarcavilla.org>
> Date:   Fri Nov 11 18:11:34 2011 +0000
>
>     Modify naming of queries into the p2m
>     [...]
>     Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
>     Acked-by: Tim Deegan <tim@xen.org>
>     Committed-by: Keir Fraser <keir@xen.org>
>
>> It's obviously correct and fixes a problem, so it can be applied to 4.6
>> tree.
> FWIW I think so too, but I'm hesitant to apply without a maintainer(/Jan)'s
> ack. I think this can probably wait until next week? 
>
>>>  xen/arch/x86/mm.c |    9 +--------
> George is the current "X86 MEMORY MANAGEMENT" maintainer, which is
> xen/arch/x86/mm/*, should xen/arch/x86/mm.c be included there too?

Oops - I hadn't even twigged.

Despite being in mm.c, this really isn't memory management and is just
general x86 behaviour, which is covered by my maintership role.

Not that I expect anyone (maintainer or not) to have a problem with this
change.

FWIW, following the Linux LDT thread, I have a bucket load of changes to
do with GDT and LDT handling for PV guests.  While most of that is
definitely 4.7 material, I felt that this fix alone should be fixed in 4.6

~Andrew