From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40577) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1f9CuW-0005y5-SC for qemu-devel@nongnu.org; Thu, 19 Apr 2018 12:59:53 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1f9CuT-0008Ex-OE for qemu-devel@nongnu.org; Thu, 19 Apr 2018 12:59:52 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:59384 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1f9CuT-0008EI-Ik for qemu-devel@nongnu.org; Thu, 19 Apr 2018 12:59:49 -0400 References: <20180412151232.17506-1-tiwei.bie@intel.com> <20180412151232.17506-7-tiwei.bie@intel.com> <20180418192154-mutt-send-email-mst@kernel.org> <20180419111439.i6gfhnept6wy7uzp@debian> <20180419182035-mutt-send-email-mst@kernel.org> From: Paolo Bonzini Message-ID: <28ab1675-15ae-dab4-fd71-7632666f57fc@redhat.com> Date: Thu, 19 Apr 2018 18:59:39 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Liang, Cunming" , "Michael S. Tsirkin" Cc: "Bie, Tiwei" , "jasowang@redhat.com" , "alex.williamson@redhat.com" , "stefanha@redhat.com" , "qemu-devel@nongnu.org" , "virtio-dev@lists.oasis-open.org" , "Daly, Dan" , "Tan, Jianfeng" , "Wang, Zhihong" , "Wang, Xiao W" On 19/04/2018 18:52, Liang, Cunming wrote: >>> Oh you are right. >>> >>> So it's only needed for non-intel platforms or when packets are >>> in WC memory then. And I don't know whether dpdk ever puts >>> packets in WC memory. >>> >>> I guess we'll cross this bridge when we get to it. >> Non-TSO architectures seem important... > > I'm not familiar with Non-TSO, trying to understand the difference > according to the feature set. Let's say non-TSO architectures do not > set 'weak_barriers'. Then mandatory barrier is used for software. HW > offload on that platform would choose different feature set against > software? If it's not, essentially we're worried about live migration > from a TSO to a non-TSO architectures platform? I'm worried about live migration from software virtio to hardware virtio on non-TSO architectures. For example, on ARM you would have a "dmb ishst" (smp_wmb) for software virtio and a "dsb st" (wmb) or "dmb oshst" (dma_wmb) for hardware virtio. For this to work, you would have to set up the VM so that it uses the heavier barriers from the beginning, even when backed by software virtio. Paolo From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-dev-return-3890-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [66.179.20.138]) by lists.oasis-open.org (Postfix) with ESMTP id 1FDF358191A2 for ; Thu, 19 Apr 2018 09:59:59 -0700 (PDT) References: <20180412151232.17506-1-tiwei.bie@intel.com> <20180412151232.17506-7-tiwei.bie@intel.com> <20180418192154-mutt-send-email-mst@kernel.org> <20180419111439.i6gfhnept6wy7uzp@debian> <20180419182035-mutt-send-email-mst@kernel.org> From: Paolo Bonzini Message-ID: <28ab1675-15ae-dab4-fd71-7632666f57fc@redhat.com> Date: Thu, 19 Apr 2018 18:59:39 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [virtio-dev] RE: [PATCH v3 6/6] vhost-user: support registering external host notifiers To: "Liang, Cunming" , "Michael S. Tsirkin" Cc: "Bie, Tiwei" , "jasowang@redhat.com" , "alex.williamson@redhat.com" , "stefanha@redhat.com" , "qemu-devel@nongnu.org" , "virtio-dev@lists.oasis-open.org" , "Daly, Dan" , "Tan, Jianfeng" , "Wang, Zhihong" , "Wang, Xiao W" List-ID: On 19/04/2018 18:52, Liang, Cunming wrote: >>> Oh you are right. >>> >>> So it's only needed for non-intel platforms or when packets are >>> in WC memory then. And I don't know whether dpdk ever puts >>> packets in WC memory. >>> >>> I guess we'll cross this bridge when we get to it. >> Non-TSO architectures seem important... > > I'm not familiar with Non-TSO, trying to understand the difference > according to the feature set. Let's say non-TSO architectures do not > set 'weak_barriers'. Then mandatory barrier is used for software. HW > offload on that platform would choose different feature set against > software? If it's not, essentially we're worried about live migration > from a TSO to a non-TSO architectures platform? I'm worried about live migration from software virtio to hardware virtio on non-TSO architectures. For example, on ARM you would have a "dmb ishst" (smp_wmb) for software virtio and a "dsb st" (wmb) or "dmb oshst" (dma_wmb) for hardware virtio. For this to work, you would have to set up the VM so that it uses the heavier barriers from the beginning, even when backed by software virtio. Paolo --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org