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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 77706C433FE for ; Thu, 10 Mar 2022 13:04:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242280AbiCJNFj (ORCPT ); Thu, 10 Mar 2022 08:05:39 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52558 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242159AbiCJNFi (ORCPT ); Thu, 10 Mar 2022 08:05:38 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 3040214ACB0 for ; Thu, 10 Mar 2022 05:04:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1646917476; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=bdyc38wZ2iH9r3WKn+t93MmqB7rhoqJHCNg2E4+WN7U=; b=SpEFkZV/zuSBLNW8fJmhMLfrDvIjSwHymuv1ZMoL918rp13XovnL7A5lI9zLVaARMwDDnj XkRR7Xo6BCX11czI383MreDHa6TLGpqNouK2l1tP5aovX8BNlZrk6qojnFbtcyQPB2Vtbw VX6B22kxhOVzZ7hUJTHa+f7qpP5LT4M= Received: from mail-wr1-f70.google.com (mail-wr1-f70.google.com [209.85.221.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-172-S0kk1mq6NFSKQYOYuLVeRA-1; Thu, 10 Mar 2022 08:04:35 -0500 X-MC-Unique: S0kk1mq6NFSKQYOYuLVeRA-1 Received: by mail-wr1-f70.google.com with SMTP id n4-20020a5d4844000000b001f1ed76e943so1677399wrs.22 for ; Thu, 10 Mar 2022 05:04:34 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=bdyc38wZ2iH9r3WKn+t93MmqB7rhoqJHCNg2E4+WN7U=; b=7Qu/uD2jd2dqOureS7VrVj7NAsjemKdINHsPlNp24k/DiucH4w5fVbWbWF5Z1Oqtla ZawVuMYGIUpLCemkcQ2ugCy2bCd2N2A2yno1gFxX5SpgXZzSuT24dNXz6zwxvrQbqhJg ERLjl+Ujco21H7g8l8cOJb0ybtCmoi3yYMT5iA0xYLABCUrDtczOpwKskcvW6mKAh7L6 qREUZCx5QjpCRS2m/YcWT7l3QFeJzXoq5jKLWVAqXVOGefjgsvgQa7mY1C0wDU60GcKj AwXeQ5pM8seTl/1o8dK+TyBedIgkjjqs0Djj2cYsXWGoIeplE6FPUI6SUTp1gRgbA3nf oL3A== X-Gm-Message-State: AOAM532B+7Pvs7evzEsr9/tZXyRKQARpkWDbRpk+INOSuY6hIrG5y0qx +C8K5XPzhukbHesKmbWJgiQmn7jx7hProYOaa2Xy+Kk+8baECVPt46V/a3b1hK0pEZSykWzIK8H KS/E3JGLzMEMHpQdv X-Received: by 2002:adf:de8b:0:b0:203:7a51:9cd2 with SMTP id w11-20020adfde8b000000b002037a519cd2mr3317893wrl.596.1646917473921; Thu, 10 Mar 2022 05:04:33 -0800 (PST) X-Google-Smtp-Source: ABdhPJwFfnvrAlCV1H1HX6YvfASjcXGHtL+mw46jnJLY1T+Nd4lSI9nkDqnoZvkqahCBW9kDpy9wvg== X-Received: by 2002:adf:de8b:0:b0:203:7a51:9cd2 with SMTP id w11-20020adfde8b000000b002037a519cd2mr3317878wrl.596.1646917473640; Thu, 10 Mar 2022 05:04:33 -0800 (PST) Received: from redhat.com ([2.53.27.107]) by smtp.gmail.com with ESMTPSA id u10-20020adfa18a000000b001f04c24afe7sm4182953wru.41.2022.03.10.05.04.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Mar 2022 05:04:32 -0800 (PST) Date: Thu, 10 Mar 2022 08:04:27 -0500 From: "Michael S. Tsirkin" To: Xuan Zhuo Cc: virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, Jeff Dike , Richard Weinberger , Anton Ivanov , Jason Wang , "David S. Miller" , Jakub Kicinski , Hans de Goede , Mark Gross , Vadim Pasternak , Bjorn Andersson , Mathieu Poirier , Cornelia Huck , Halil Pasic , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Alexander Gordeev , Sven Schnelle , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , Johannes Berg , Vincent Whitchurch , linux-um@lists.infradead.org, platform-driver-x86@vger.kernel.org, linux-remoteproc@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH v7 09/26] virtio_ring: split: implement virtqueue_reset_vring_split() Message-ID: <20220310080212-mutt-send-email-mst@kernel.org> References: <20220308123518.33800-1-xuanzhuo@linux.alibaba.com> <20220308123518.33800-10-xuanzhuo@linux.alibaba.com> <20220310015418-mutt-send-email-mst@kernel.org> <1646896623.3794115-2-xuanzhuo@linux.alibaba.com> <20220310025930-mutt-send-email-mst@kernel.org> <1646900056.7775025-1-xuanzhuo@linux.alibaba.com> <20220310071335-mutt-send-email-mst@kernel.org> <1646915610.3936472-1-xuanzhuo@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1646915610.3936472-1-xuanzhuo@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Mar 10, 2022 at 08:33:30PM +0800, Xuan Zhuo wrote: > On Thu, 10 Mar 2022 07:17:09 -0500, "Michael S. Tsirkin" wrote: > > On Thu, Mar 10, 2022 at 04:14:16PM +0800, Xuan Zhuo wrote: > > > On Thu, 10 Mar 2022 03:07:22 -0500, "Michael S. Tsirkin" wrote: > > > > On Thu, Mar 10, 2022 at 03:17:03PM +0800, Xuan Zhuo wrote: > > > > > On Thu, 10 Mar 2022 02:00:39 -0500, "Michael S. Tsirkin" wrote: > > > > > > On Tue, Mar 08, 2022 at 08:35:01PM +0800, Xuan Zhuo wrote: > > > > > > > virtio ring supports reset. > > > > > > > > > > > > > > Queue reset is divided into several stages. > > > > > > > > > > > > > > 1. notify device queue reset > > > > > > > 2. vring release > > > > > > > 3. attach new vring > > > > > > > 4. notify device queue re-enable > > > > > > > > > > > > > > After the first step is completed, the vring reset operation can be > > > > > > > performed. If the newly set vring num does not change, then just reset > > > > > > > the vq related value. > > > > > > > > > > > > > > Otherwise, the vring will be released and the vring will be reallocated. > > > > > > > And the vring will be attached to the vq. If this process fails, the > > > > > > > function will exit, and the state of the vq will be the vring release > > > > > > > state. You can call this function again to reallocate the vring. > > > > > > > > > > > > > > In addition, vring_align, may_reduce_num are necessary for reallocating > > > > > > > vring, so they are retained when creating vq. > > > > > > > > > > > > > > Signed-off-by: Xuan Zhuo > > > > > > > --- > > > > > > > drivers/virtio/virtio_ring.c | 69 ++++++++++++++++++++++++++++++++++++ > > > > > > > 1 file changed, 69 insertions(+) > > > > > > > > > > > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > > > > > > index e0422c04c903..148fb1fd3d5a 100644 > > > > > > > --- a/drivers/virtio/virtio_ring.c > > > > > > > +++ b/drivers/virtio/virtio_ring.c > > > > > > > @@ -158,6 +158,12 @@ struct vring_virtqueue { > > > > > > > /* DMA address and size information */ > > > > > > > dma_addr_t queue_dma_addr; > > > > > > > size_t queue_size_in_bytes; > > > > > > > + > > > > > > > + /* The parameters for creating vrings are reserved for > > > > > > > + * creating new vrings when enabling reset queue. > > > > > > > + */ > > > > > > > + u32 vring_align; > > > > > > > + bool may_reduce_num; > > > > > > > } split; > > > > > > > > > > > > > > /* Available for packed ring */ > > > > > > > @@ -217,6 +223,12 @@ struct vring_virtqueue { > > > > > > > #endif > > > > > > > }; > > > > > > > > > > > > > > +static void vring_free(struct virtqueue *vq); > > > > > > > +static void __vring_virtqueue_init_split(struct vring_virtqueue *vq, > > > > > > > + struct virtio_device *vdev); > > > > > > > +static int __vring_virtqueue_attach_split(struct vring_virtqueue *vq, > > > > > > > + struct virtio_device *vdev, > > > > > > > + struct vring vring); > > > > > > > > > > > > > > /* > > > > > > > * Helpers. > > > > > > > @@ -1012,6 +1024,8 @@ static struct virtqueue *vring_create_virtqueue_split( > > > > > > > return NULL; > > > > > > > } > > > > > > > > > > > > > > + to_vvq(vq)->split.vring_align = vring_align; > > > > > > > + to_vvq(vq)->split.may_reduce_num = may_reduce_num; > > > > > > > to_vvq(vq)->split.queue_dma_addr = vring.dma_addr; > > > > > > > to_vvq(vq)->split.queue_size_in_bytes = vring.queue_size_in_bytes; > > > > > > > to_vvq(vq)->we_own_ring = true; > > > > > > > @@ -1019,6 +1033,59 @@ static struct virtqueue *vring_create_virtqueue_split( > > > > > > > return vq; > > > > > > > } > > > > > > > > > > > > > > +static int virtqueue_reset_vring_split(struct virtqueue *_vq, u32 num) > > > > > > > +{ > > > > > > > + struct vring_virtqueue *vq = to_vvq(_vq); > > > > > > > + struct virtio_device *vdev = _vq->vdev; > > > > > > > + struct vring_split vring; > > > > > > > + int err; > > > > > > > + > > > > > > > + if (num > _vq->num_max) > > > > > > > + return -E2BIG; > > > > > > > + > > > > > > > + switch (vq->vq.reset) { > > > > > > > + case VIRTIO_VQ_RESET_STEP_NONE: > > > > > > > + return -ENOENT; > > > > > > > + > > > > > > > + case VIRTIO_VQ_RESET_STEP_VRING_ATTACH: > > > > > > > + case VIRTIO_VQ_RESET_STEP_DEVICE: > > > > > > > + if (vq->split.vring.num == num || !num) > > > > > > > + break; > > > > > > > + > > > > > > > + vring_free(_vq); > > > > > > > + > > > > > > > + fallthrough; > > > > > > > + > > > > > > > + case VIRTIO_VQ_RESET_STEP_VRING_RELEASE: > > > > > > > + if (!num) > > > > > > > + num = vq->split.vring.num; > > > > > > > + > > > > > > > + err = vring_create_vring_split(&vring, vdev, > > > > > > > + vq->split.vring_align, > > > > > > > + vq->weak_barriers, > > > > > > > + vq->split.may_reduce_num, num); > > > > > > > + if (err) > > > > > > > + return -ENOMEM; > > > > > > > + > > > > > > > + err = __vring_virtqueue_attach_split(vq, vdev, vring.vring); > > > > > > > + if (err) { > > > > > > > + vring_free_queue(vdev, vring.queue_size_in_bytes, > > > > > > > + vring.queue, > > > > > > > + vring.dma_addr); > > > > > > > + return -ENOMEM; > > > > > > > + } > > > > > > > + > > > > > > > + vq->split.queue_dma_addr = vring.dma_addr; > > > > > > > + vq->split.queue_size_in_bytes = vring.queue_size_in_bytes; > > > > > > > + } > > > > > > > + > > > > > > > + __vring_virtqueue_init_split(vq, vdev); > > > > > > > + vq->we_own_ring = true; > > > > > > > + vq->vq.reset = VIRTIO_VQ_RESET_STEP_VRING_ATTACH; > > > > > > > + > > > > > > > + return 0; > > > > > > > +} > > > > > > > + > > > > > > > > > > > > I kind of dislike this state machine. > > > > > > > > > > > > Hacks like special-casing num = 0 to mean "reset" are especially > > > > > > confusing. > > > > > > > > > > I'm removing it. I'll say in the function description that this function is > > > > > currently only called when vq has been reset. I'm no longer checking it based on > > > > > state. > > > > > > > > > > > > > > > > > And as Jason points out, when we want a resize then yes this currently > > > > > > implies reset but that is an implementation detail. > > > > > > > > > > > > There should be a way to just make these cases separate functions > > > > > > and then use them to compose consistent external APIs. > > > > > > > > > > Yes, virtqueue_resize_split() is fine for ethtool -G. > > > > > > > > > > But in the case of AF_XDP, just execute reset to free the buffer. The name > > > > > virtqueue_reset_vring_split() I think can cover both cases. Or we use two apis > > > > > to handle both scenarios? > > > > > > > > > > Or can anyone think of a better name. ^_^ > > > > > > > > > > Thanks. > > > > > > > > > > > > I'd say resize should be called resize and reset should be called reset. > > > > > > > > > OK, I'll change it to resize here. > > > > > > But I want to know that when I implement virtio-net to support AF_XDP, its > > > requirement is to release all submitted buffers. Then should I add a new api > > > such as virtqueue_reset_vring()? > > > > Sounds like a reasonable name. > > > > > > > > > > The big issue is a sane API for resize. Ideally it would resubmit > > > > buffers which did not get used. Question is what to do > > > > about buffers which don't fit (if ring has been downsized)? > > > > Maybe a callback that will handle them? > > > > And then what? Queue them up and readd later? Drop? > > > > If we drop we should drop from the head not the tail ... > > > > > > It's a good idea, let's implement it later. > > > > > > Thanks. > > > > Well ... not sure how you are going to support resize > > if you don't know what to do with buffers that were > > in the ring. > > The current solution is to call virtqueue_detach_unused_buf() to release buffers > before resize ring. > > Thanks. This requires basically a richer api: - stop - detach - resize - start with a callback you would just have a resize, and the fact it resets internally becomes an implementation detail. -- MST