Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1949639AbdD1SCv (ORCPT ); Fri, 28 Apr 2017 14:02:51 -0400 Received: from mx2.suse.de ([195.135.220.15]:53251 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1949400AbdD1SCb (ORCPT ); Fri, 28 Apr 2017 14:02:31 -0400 Subject: Re: [PATCH] xen: Revert commits da72ff5bfcb0 and 72a9b186292d To: Boris Ostrovsky References: <1493060693-29786-1-git-send-email-boris.ostrovsky@oracle.com> Cc: karahmed@amazon.de, sstabellini@kernel.org, xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org From: Juergen Gross Message-ID: Date: Fri, 28 Apr 2017 20:02:29 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <1493060693-29786-1-git-send-email-boris.ostrovsky@oracle.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1672 Lines: 40 On 24/04/17 21:04, Boris Ostrovsky wrote: > Recent discussion (http://marc.info/?l=xen-devel&m=149192184523741) > established that commit 72a9b186292d ("xen: Remove event channel > notification through Xen PCI platform device") (and thus commit > da72ff5bfcb0 ("partially revert "xen: Remove event channel > notification through Xen PCI platform device"")) are unnecessary and, > in fact, prevent HVM guests from booting on Xen releases prior to 4.0 > > Therefore we revert both of those commits. > > The summary of that discussion is below: > > Here is the brief summary of the current situation: > > Before the offending commit (72a9b186292): > > 1) INTx does not work because of the reset_watches path. > 2) The reset_watches path is only taken if you have Xen > 4.0 > 3) The Linux Kernel by default will use vector inject if the hypervisor > support. So even INTx does not work no body running the kernel with > Xen > 4.0 would notice. Unless he explicitly disabled this feature > either in the kernel or in Xen (and this can only be disabled by > modifying the code, not user-supported way to do it). > > After the offending commit (+ partial revert): > > 1) INTx is no longer support for HVM (only for PV guests). > 2) Any HVM guest The kernel will not boot on Xen < 4.0 which does > not have vector injection support. Since the only other mode > supported is INTx which. > > So based on this summary, I think before commit (72a9b186292) we were > in much better position from a user point of view. > > Signed-off-by: Boris Ostrovsky Pushed to xen/tip for-linus-4.12 Juergen