From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCH] x86: wrap kexec feature with CONFIG_KEXEC Date: Tue, 1 Sep 2015 11:36:17 +0100 Message-ID: <1441103777.27618.31.camel@citrix.com> References: <1440686870-19104-1-git-send-email-jonathan.creekmore@gmail.com> <55DF2C57.8030100@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1ZWivd-0004nI-VR for xen-devel@lists.xenproject.org; Tue, 01 Sep 2015 10:36:38 +0000 In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jonathan Creekmore , David Vrabel Cc: xen-devel@lists.xenproject.org, keir@xen.org, jbeulich@suse.com, andrew.cooper3@citrix.com List-Id: xen-devel@lists.xenproject.org On Thu, 2015-08-27 at 10:44 -0500, Jonathan Creekmore wrote: > > > > On Aug 27, 2015, at 10:27 AM, David Vrabel > > wrote: > > > > On 27/08/15 15:47, Jonathan Creekmore wrote: > > > Add the appropriate #if checks around the kexec code in the x86 > > > codebase > > > so that the feature can actually be turned off by the flag instead of > > > always required to be enabled on x86. > > > > What's your use case for this? > > > > The use case is for a slimmed down version of the hypervisor that can be > used as a security hypervisor, exposing as little extra functionality as > possible. When looking for features to trim out to reduce the attack > surface, I saw the flag for KEXEC and wanted to disable that, then ran > into compile problems. Can this not be achieved at runtime with XSM? In general (i.e. not 100% consistently, I think) we have tended to avoid making things user-facing compile time options. Many of the existing CONFIG_* and HAVE_* are really about things which are arch dependent, or require specific porting to each arch etc. I think the KEXEC flag is one of those. This keeps the test matrix more reasonable (unlike e.g. Linux's Kconfig) and also helps us by ensuring that users are mostly running one of a small number of possible configs. I slightly fear that after Kexec you are going to want to strip out more and more stuff... Ian.