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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 DFACCC04AA5 for ; Mon, 15 Oct 2018 10:25:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AD6C92064A for ; Mon, 15 Oct 2018 10:25:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AD6C92064A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726778AbeJOSJy (ORCPT ); Mon, 15 Oct 2018 14:09:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54658 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726273AbeJOSJy (ORCPT ); Mon, 15 Oct 2018 14:09:54 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 34A683082A46; Mon, 15 Oct 2018 10:25:16 +0000 (UTC) Received: from redhat.com (ovpn-120-81.rdu2.redhat.com [10.10.120.81]) by smtp.corp.redhat.com (Postfix) with ESMTP id 37D131726D; Mon, 15 Oct 2018 10:25:09 +0000 (UTC) Date: Mon, 15 Oct 2018 06:25:08 -0400 From: "Michael S. Tsirkin" To: Jason Wang Cc: Tiwei Bie , kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, wexu@redhat.com, jfreimann@redhat.com, maxime.coquelin@redhat.com Subject: Re: [PATCH net-next V2 6/8] vhost: packed ring support Message-ID: <20181015062241-mutt-send-email-mst@kernel.org> References: <1531711691-6769-1-git-send-email-jasowang@redhat.com> <1531711691-6769-7-git-send-email-jasowang@redhat.com> <20181012143244.GA28400@debian> <20181012131812-mutt-send-email-mst@kernel.org> <447f47fa-32dd-a408-dd81-13a9839e0748@redhat.com> <20181014224208-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Mon, 15 Oct 2018 10:25:16 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 15, 2018 at 10:51:06AM +0800, Jason Wang wrote: > > > On 2018年10月15日 10:43, Michael S. Tsirkin wrote: > > On Mon, Oct 15, 2018 at 10:22:33AM +0800, Jason Wang wrote: > > > > > > On 2018年10月13日 01:23, Michael S. Tsirkin wrote: > > > > On Fri, Oct 12, 2018 at 10:32:44PM +0800, Tiwei Bie wrote: > > > > > On Mon, Jul 16, 2018 at 11:28:09AM +0800, Jason Wang wrote: > > > > > [...] > > > > > > @@ -1367,10 +1397,48 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg > > > > > > vq->last_avail_idx = s.num; > > > > > > /* Forget the cached index value. */ > > > > > > vq->avail_idx = vq->last_avail_idx; > > > > > > + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) { > > > > > > + vq->last_avail_wrap_counter = wrap_counter; > > > > > > + vq->avail_wrap_counter = vq->last_avail_wrap_counter; > > > > > > + } > > > > > > break; > > > > > > case VHOST_GET_VRING_BASE: > > > > > > s.index = idx; > > > > > > s.num = vq->last_avail_idx; > > > > > > + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) > > > > > > + s.num |= vq->last_avail_wrap_counter << 31; > > > > > > + if (copy_to_user(argp, &s, sizeof(s))) > > > > > > + r = -EFAULT; > > > > > > + break; > > > > > > + case VHOST_SET_VRING_USED_BASE: > > > > > > + /* Moving base with an active backend? > > > > > > + * You don't want to do that. > > > > > > + */ > > > > > > + if (vq->private_data) { > > > > > > + r = -EBUSY; > > > > > > + break; > > > > > > + } > > > > > > + if (copy_from_user(&s, argp, sizeof(s))) { > > > > > > + r = -EFAULT; > > > > > > + break; > > > > > > + } > > > > > > + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) { > > > > > > + wrap_counter = s.num >> 31; > > > > > > + s.num &= ~(1 << 31); > > > > > > + } > > > > > > + if (s.num > 0xffff) { > > > > > > + r = -EINVAL; > > > > > > + break; > > > > > > + } > > > > > Do we want to put wrap_counter at bit 15? > > > > I think I second that - seems to be consistent with > > > > e.g. event suppression structure and the proposed > > > > extension to driver notifications. > > > Ok, I assumes packed virtqueue support 64K but looks not. I can change it to > > > bit 15 and GET_VRING_BASE need to be changed as well. > > > > > > > > > > > > If put wrap_counter at bit 31, the check (s.num > 0xffff) > > > > > won't be able to catch the illegal index 0x8000~0xffff for > > > > > packed ring. > > > > > > > > Do we need to clarify this in the spec? > > Isn't this all internal vhost stuff? > > I meant the illegal index 0x8000-0xffff. It does say packed virtqueues support up to 2 15 entries each. But yes we can add a requirement that devices do not expose larger rings. Split does not support 2**16 either, right? With 2**16 enties avail index becomes 0 and ring looks empty. > > > > > > > > > + vq->last_used_idx = s.num; > > > > > > + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) > > > > > > + vq->last_used_wrap_counter = wrap_counter; > > > > > > + break; > > > > > > + case VHOST_GET_VRING_USED_BASE: > > > > > Do we need the new VHOST_GET_VRING_USED_BASE and > > > > > VHOST_SET_VRING_USED_BASE ops? > > > > > > > > > > We are going to merge below series in DPDK: > > > > > > > > > > http://patches.dpdk.org/patch/45874/ > > > > > > > > > > We may need to reach an agreement first. > > > If we agree that 64K virtqueue won't be supported, I'm ok with either. > > Well the spec says right at the beginning: > > > > Packed virtqueues support up to 2 15 entries each. > > Ok. I get it. > > Then I can change vhost to match what dpdk did. > > Thanks > > > > > > > > Btw the code assumes used_wrap_counter is equal to avail_wrap_counter which > > > looks wrong? > > > > > > Thanks > > > > > > > > > + s.index = idx; > > > > > > + s.num = vq->last_used_idx; > > > > > > + if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) > > > > > > + s.num |= vq->last_used_wrap_counter << 31; > > > > > > if (copy_to_user(argp, &s, sizeof s)) > > > > > > r = -EFAULT; > > > > > > break; > > > > > [...]