From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Ostrovsky Subject: Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit Date: Mon, 16 Nov 2015 15:31:52 -0500 Message-ID: <564A3D38.4030607__2569.57135065949$1447706030$gmane$org@oracle.com> References: <1447456706-24347-1-git-send-email-boris.ostrovsky@oracle.com> <56468D24.8030801@oracle.com> <564A0371.2040104@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: 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: Andy Lutomirski Cc: David Vrabel , Borislav Petkov , "linux-kernel@vger.kernel.org" , xen-devel List-Id: xen-devel@lists.xenproject.org On 11/16/2015 02:03 PM, Andy Lutomirski wrote: > It's still a waste of effort, though. Also, I'd eventually like the > number of places in Xen code in which rsp/esp is invalid to be exactly > zero, and this approach makes this harder or even impossible. That's what PVH is going to do. > Does PVH hook into the entry asm code at all? I thought it was just > boot code and drivers. Not the current version --- it starts with xen_start_kernel(). But we are currently changing it and my plan is to have a small stub executed initially (to set bootparams and such) and then jump to startup_{32|64}(). > > In any case, someone needs to do some serious review and cleanup on > the whole paravirt op mess. We have a bunch of paravirt ops that > serve little purpose. > > The paravirt infrastructure is a bit weird, too: it seems to > effectively have four states for each patch site. There's: > > 1. The initial state, which is unoptimized and works on native. > Presumably any of these that happen early also need to work, if > slowly, on Xen. Not on PV (and as of today, on PVH) --- we start directly from xen_start_kernel(). I.e. from step 2. > > 2. The Xen state without text patching. I'm not actually sure why > this exists at all. Are there pvops that need to switch too early for > us to patch the text? I don't think so. -boris