From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A8C3DC43603 for ; Thu, 12 Dec 2019 06:07:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7423A21655 for ; Thu, 12 Dec 2019 06:07:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726833AbfLLGHK (ORCPT ); Thu, 12 Dec 2019 01:07:10 -0500 Received: from mx2.suse.de ([195.135.220.15]:33802 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726784AbfLLGHJ (ORCPT ); Thu, 12 Dec 2019 01:07:09 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id CAD5EB2C2; Thu, 12 Dec 2019 06:07:07 +0000 (UTC) Subject: Re: [PATCH v3 4/4] xen-blkback: support dynamic unbind/bind To: Paul Durrant , xen-devel@lists.xenproject.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Konrad Rzeszutek Wilk , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Jens Axboe , Boris Ostrovsky , Stefano Stabellini References: <20191211152956.5168-1-pdurrant@amazon.com> <20191211152956.5168-5-pdurrant@amazon.com> From: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= Message-ID: Date: Thu, 12 Dec 2019 07:07:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.1 MIME-Version: 1.0 In-Reply-To: <20191211152956.5168-5-pdurrant@amazon.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 11.12.19 16:29, Paul Durrant wrote: > By simply re-attaching to shared rings during connect_ring() rather than > assuming they are freshly allocated (i.e assuming the counters are zero) > it is possible for vbd instances to be unbound and re-bound from and to > (respectively) a running guest. > > This has been tested by running: > > while true; > do fio --name=randwrite --ioengine=libaio --iodepth=16 \ > --rw=randwrite --bs=4k --direct=1 --size=1G --verify=crc32; > done > > in a PV guest whilst running: > > while true; > do echo vbd-$DOMID-$VBD >unbind; > echo unbound; > sleep 5; > echo vbd-$DOMID-$VBD >bind; > echo bound; > sleep 3; > done > > in dom0 from /sys/bus/xen-backend/drivers/vbd to continuously unbind and > re-bind its system disk image. > > This is a highly useful feature for a backend module as it allows it to be > unloaded and re-loaded (i.e. updated) without requiring domUs to be halted. > This was also tested by running: > > while true; > do echo vbd-$DOMID-$VBD >unbind; > echo unbound; > sleep 5; > rmmod xen-blkback; > echo unloaded; > sleep 1; > modprobe xen-blkback; > echo bound; > cd $(pwd); > sleep 3; > done > > in dom0 whilst running the same loop as above in the (single) PV guest. > > Some (less stressful) testing has also been done using a Windows HVM guest > with the latest 9.0 PV drivers installed. > > Signed-off-by: Paul Durrant Reviewed-by: Juergen Gross Juergen