From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id DBCC01B5DD for ; Fri, 3 Nov 2017 15:28:45 +0100 (CET) Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D37CF2020F; Fri, 3 Nov 2017 14:28:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com D37CF2020F Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=maxime.coquelin@redhat.com Received: from [10.36.112.52] (ovpn-112-52.ams2.redhat.com [10.36.112.52]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BF6D45EE1D; Fri, 3 Nov 2017 14:28:38 +0000 (UTC) To: Yuanhan Liu Cc: "Kavanagh, Mark B" , "dev@dpdk.org" , "Horton, Remy" , "Bie, Tiwei" , "mst@redhat.com" , "jfreiman@redhat.com" , "vkaplans@redhat.com" , "jasowang@redhat.com" , "Mcnamara, John" , "Loftus, Ciara" , "Stokes, Ian" , Thomas Monjalon References: <20171005083627.27828-1-maxime.coquelin@redhat.com> <20171005083627.27828-2-maxime.coquelin@redhat.com> <20171103130510.GB12931@yliu-home> From: Maxime Coquelin Message-ID: Date: Fri, 3 Nov 2017 15:28:36 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: <20171103130510.GB12931@yliu-home> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Fri, 03 Nov 2017 14:28:45 +0000 (UTC) Subject: Re: [dpdk-dev] [PATCH v3 01/19] Revert "vhost: workaround MQ fails to startup" X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 03 Nov 2017 14:28:46 -0000 On 11/03/2017 02:05 PM, Yuanhan Liu wrote: > On Thu, Nov 02, 2017 at 10:40:26AM +0100, Maxime Coquelin wrote: >>> Moving from QEMU v2.7.0 to v2.10.0 resolves the issue. However, herein lies the issue: QEMU v2.10.0 was only released in August of this year; anecdotally, we know that many OvS-DPDK customers use older versions of QEMU (typically, v2.7.0), and are likely un[able|willing] to move. With this patch, a hard dependency on QEMU v2.10 is created for users who want to use the vHU multiq feature in DPDK v17.11 (and subsequently, the upcoming OvS v2.9.0), which IMO will likely be unacceptable for many. >> >> Do you mean that upstream Qemu v2.7.0 is used in production? >> I would expect the customers to use a distro Qemu which should contain >> relevant fixes, or follow upstream's stable branches. >> >> FYI, Qemu v2.9.1 contains a backport of the fix. >> >>> One potential solution to this problem is to introduce a compile-time option that would allow the user to [dis|en]able the VHOST_USER_PROTOCOL_F_REPLY_ACK feature - is that something that would be acceptable to you Maxime? >> >> Yes, that's one option, but: >> 1. VHOST_USER_PROTOCOL_F_REPLY_ACK enabled should be the default >> 2. VHOST_USER_PROTOCOL_F_REPLY_ACK disabled will be less extensively >> tested. >> >> Yuanhan, what do you think? > > My suggestion is to still disable it by default. Qemu 2.7 - 2.9 (inclusive) > is a pretty big range, that I think quite many people would hit this issue Ok, then what about adding a new flag to rte_vhost_driver_register(), as done for tx zero copy to enable IOMMU feature? If flag is unset, then we mask out both IOMMU virtio feature flag and REPLY_ACK protocol feature flag. For a while this flag will be unset by default, not to break these deprecated and unmaintained Qemu versions. But I think at some point we should make it enabled by default, as it would be sad not to benefit from this security feature. This change will have an impact on OVS, as it will need a new vhost-user port option to enable IOMMU feature. Thing that is transparent to OVS currently. Mark, Yuanhan, does that sound good to you? Maxime > --yliu >