From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752839AbcGYNjT (ORCPT ); Mon, 25 Jul 2016 09:39:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38296 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752161AbcGYNjH (ORCPT ); Mon, 25 Jul 2016 09:39:07 -0400 From: Vitaly Kuznetsov To: Julien Grall Cc: David Vrabel , xen-devel@lists.xenproject.org, Juergen Gross , Stefano Stabellini , Andrew Cooper , x86@kernel.org, linux-kernel@vger.kernel.org, Ingo Molnar , Jan Beulich , "H. Peter Anvin" , Boris Ostrovsky , Thomas Gleixner Subject: Re: [Xen-devel] [PATCH linux v2 0/9] xen: pvhvm: support bootup on secondary vCPUs References: <1467302203-22399-1-git-send-email-vkuznets@redhat.com> <57960843.9070602@citrix.com> Date: Mon, 25 Jul 2016 15:39:02 +0200 In-Reply-To: (Julien Grall's message of "Mon, 25 Jul 2016 14:17:23 +0100") Message-ID: <87bn1lx2fd.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.95 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Mon, 25 Jul 2016 13:39:06 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Julien Grall writes: > Hi David, > > On 25/07/16 13:38, David Vrabel wrote: >> On 30/06/16 16:56, Vitaly Kuznetsov wrote: >>> It may happen that Xen's and Linux's ideas of vCPU id diverge. In >>> particular, when we crash on a secondary vCPU we may want to do kdump >>> and unlike plain kexec where we do migrate_to_reboot_cpu() we try booting >>> on the vCPU which crashed. This doesn't work very well for PVHVM guests as >>> we have a number of hypercalls where we pass vCPU id as a parameter. These >>> hypercalls either fail or do something unexpected. To solve the issue we >>> need to have a mapping between Linux's and Xen's vCPU ids. >>> >>> This series solves the issue for x86 PVHVM guests. PV guests don't (and >>> probably won't) support kdump so I always assume Xen's vCPU id == Linux's >>> vCPU id. ARM guests will probably need to get proper mapping once we start >>> supporting kexec/kdump there. >> >> Applied to for-linus-4.8, thanks. > > It would have been nice to send a ping before applying. This patch > series is containing Xen ARM code which has not been acked by Stefano, > nor had feedback from ARM side. > > For instance given that all the hypercalls are representing a "vcpu > id" using "uint32_t" it is a bit weird to use "int" to define > xen_vcpu_id (see patch #3). CPU id is usually 'int' in linux and now we pass it to all hypercalls as it is. It is a bit more convenient in the mapping I introduce as we can set it to a negative value to indicate there is no mapping available. I can definitely change that and use something like U32_MAX-1 to instead but I'm not sure it is worth it... -- Vitaly