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 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 E81BAC04EBD for ; Tue, 16 Oct 2018 13:58:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AD0A8205C9 for ; Tue, 16 Oct 2018 13:58:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AD0A8205C9 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 S1727159AbeJPVtL (ORCPT ); Tue, 16 Oct 2018 17:49:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46568 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726778AbeJPVtL (ORCPT ); Tue, 16 Oct 2018 17:49:11 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3462E65995; Tue, 16 Oct 2018 13:58:35 +0000 (UTC) Received: from [10.36.112.24] (ovpn-112-24.ams2.redhat.com [10.36.112.24]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8FDCF5D9C8; Tue, 16 Oct 2018 13:58:24 +0000 (UTC) Subject: Re: [PATCH net-next V2 6/8] vhost: packed ring support To: Jason Wang , "Michael S. Tsirkin" , Tiwei Bie Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, wexu@redhat.com, jfreimann@redhat.com 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> From: Maxime Coquelin Message-ID: <1df62bd3-3cc9-d04a-2939-4570d37faa68@redhat.com> Date: Tue, 16 Oct 2018 15:58:22 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <447f47fa-32dd-a408-dd81-13a9839e0748@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Tue, 16 Oct 2018 13:58:35 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/15/2018 04:22 AM, 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? > >>>> +        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. I'm fine to put wrap_counter at bit 15. I will post a new version of the DPDK series soon. > Btw the code assumes used_wrap_counter is equal to avail_wrap_counter > which looks wrong? For split ring, we used to set the last_used_idx to the same value as last_avail_idx as VHOST_USER_GET_VRING_BASE cannot be called while the ring is being processed, so their value is always the same at the time the request is handled. I kept the same behavior for packed ring, and so the wrap counter have to be the same. Regards, Maxime > 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; >>> [...] >