From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755866AbeEAMfF (ORCPT ); Tue, 1 May 2018 08:35:05 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:41574 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755230AbeEAMfC (ORCPT ); Tue, 1 May 2018 08:35:02 -0400 Subject: Re: [Xen-devel] [PATCH 4/4] xen/PVH: Remove reserved entry in PVH GDT To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, jgross@suse.com References: <20180430162339.17143-1-boris.ostrovsky@oracle.com> <20180430162339.17143-5-boris.ostrovsky@oracle.com> <20180501080009.wnjmno5pietptixo@MacBook-Pro-de-Roger.local> From: Boris Ostrovsky Message-ID: <5a357f3d-b66e-ca55-0601-18a89b549f4a@oracle.com> Date: Tue, 1 May 2018 08:34:53 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180501080009.wnjmno5pietptixo@MacBook-Pro-de-Roger.local> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8879 signatures=668698 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=836 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1805010126 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/01/2018 04:00 AM, Roger Pau Monné wrote: > On Mon, Apr 30, 2018 at 12:23:39PM -0400, Boris Ostrovsky wrote: >> And without it we can't use _BOOT_XX macros any longer so define new ones. > > Not being that familiar with Linux internals I'm not sure I see the > benefit of this. Isn't there a risk that some other code is going to > use the __BOOT_XX defines? The startup code we are jumping to loads their own GDT and I don't see any explicit references to segments. The reason I added this patch was that since we are adding another segment descriptor (GS) we are now using PVH-specific GDT and so we are not sharing layout with other code anymore. (Also, the new GS segment overlaps with __BOOT_TSS so I kind of broke it already there, not unintentionally). But if people think I should stick with __BOOT_XX I can drop this patch (and then probably move GS down one entry). -boris