From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 03D2815574E for ; Wed, 14 May 2025 14:19:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747232353; cv=none; b=nLo+l/i/pf3K2mv4dSXjOGUQMlEYzL5EVdARwfWF4f+MfHhpYp8rfPoJZSASMpBc3PkGAMHZQzxG58lAExI0VRGdfLE3kx9Y+Rme9HgwCUYA2vF7GqEsrzAszD+fd9ZKsU5n772gMmI+Z3b+yEJUFixWzexf2PRpTYWkk6sBZMg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747232353; c=relaxed/simple; bh=+trkrqOwGtRfvjCdrEnCp8vOa1p0gMf0XU2DERcNzsQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: In-Reply-To:Content-Type:Content-Disposition; b=ntHaUAYXlIL8y/pIa/FzbeiMFRe5ZavQmDbWVsurLIMNeUIfgnYLWS0HCEkuErh6ZCqGhi+XyOZAqwwmabaCMf//z6kWbpPWWuS+x2Lw6vD+FwwKKqN1vTCHcZFjuwWHevHXj0n8cakyzBLBtufvjlE6wX1wcKlN0fZ1lgbLamc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=ZeeCU3TT; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ZeeCU3TT" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1747232348; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1jER9mqhYV9rFG2Z4I92lsjMO3rSx/6dk5Q+rS4WXao=; b=ZeeCU3TT7453orC5PpBxjeh5u+QL5/vqUczx2cJevnHu7V0HoHIHkbVnX3pxlTHOCqMqNe f1b8ZRJmGgl8i6ER12hb13C9zSVsjASVbufSzu58EZCcGk0r7zZfmEptGuFhjf5iXoYmkH Jseo7q4Zn37Gvt+Rm42SX7FDJb8aB8w= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-437-yrPtMXRnNcuSUDUILQDeyA-1; Wed, 14 May 2025 10:19:07 -0400 X-MC-Unique: yrPtMXRnNcuSUDUILQDeyA-1 X-Mimecast-MFC-AGG-ID: yrPtMXRnNcuSUDUILQDeyA_1747232346 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-442cdf07ad9so29811085e9.2 for ; Wed, 14 May 2025 07:19:07 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1747232346; x=1747837146; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=1jER9mqhYV9rFG2Z4I92lsjMO3rSx/6dk5Q+rS4WXao=; b=jNU6i/iya2WCL8OrQMiVKIWRtd7EU04R4ZYuCVvX92GUuDaCzG7GkABL2BbPgzIGiS yVua8XT69HtpILy0x+FEx/dx59QmLqQrJ3CSaMIFxPJHxedsvdIaA9yTg5da3wUHLaKq MBMmdkncNyZWmEK/dE3ExR7e8tohs7N7P+F/lmjE2xcxzOzR381jRpX9Y/pIMAqiuwX3 pcW3nM7qsjVJx6t9S/oylrLfLhoSxrpdAcsdQeJXVBboYtQrUVcbh6M4pZHGv3yC6ZJa 0g4nB1aPmWNBBs2xk8QXeJ+kkWPr9MVGNUWwmEvllE8RWt45mjuPGPEfj1e7/WSq51cO ZGcw== X-Forwarded-Encrypted: i=1; AJvYcCWt7l19dE4rLHIQXSMH8XKaxc0o6d/9Nhe7UpSuRuMkjVdGslsqrhPIjDopo9laEWhf+QllBoKLZ1XCxRq5bQ==@lists.linux.dev X-Gm-Message-State: AOJu0YxpRYRZrMMVpXhACJLO8q3hQbAOb0B+PQzxnZOpA1iDJTmLb+QJ 6D/WXMXq0jExi2iSEc7znrlpzg76Bw3zCFavKTjdLUT/JORPqxGpbEaxN9ciGwFDK6kOjqmvv88 zG06GO/wMn5RPBiSvnMkKhJKYyf5AM9YIgDgS2D0NJH7eOcTfPhaZYp40w4Jx9A1b X-Gm-Gg: ASbGncuzO8wzSn1lvqZj9hr1oqmz8o3m3NvLyS8Gx3iPCCyYSGxBlCVzJSVrfaF0zCc ps+FlN/uAkTP2Q62Xt81LxMkQP7dHp++DoZok2KKU3L+NeWCR18TB7/OP5xyfxPKiXBksUY8Isf Gizqsh0S5Wflo4klOwVtgaigcmbmt/1V7BXLvNMGDQsILD46VUfJVedbqHqzaDZPmcamoUvwrRh pXY+YFRPPRk40bk4PfBSLJiQVwh/+SNTqfoF+bpBKD3zr7tPGK28ByylWwE/3gdZnsHgSxFsd85 XrYTtg== X-Received: by 2002:a05:600c:4f43:b0:43c:ef13:7e5e with SMTP id 5b1f17b1804b1-442f215d914mr31746185e9.26.1747232345890; Wed, 14 May 2025 07:19:05 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGEvjX5YE/uJrschNA9QCet/oxS3WILXJtmin+52ZNugqTMTF+Of4rD7RNXd3avZsU31ZOSQw== X-Received: by 2002:a05:600c:4f43:b0:43c:ef13:7e5e with SMTP id 5b1f17b1804b1-442f215d914mr31745805e9.26.1747232345407; Wed, 14 May 2025 07:19:05 -0700 (PDT) Received: from redhat.com ([2a0d:6fc0:1517:1000:ea83:8e5f:3302:3575]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-442f337db24sm30989925e9.15.2025.05.14.07.19.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 May 2025 07:19:04 -0700 (PDT) Date: Wed, 14 May 2025 10:19:02 -0400 From: "Michael S. Tsirkin" To: Jason Wang Cc: xuanzhuo@linux.alibaba.com, eperezma@redhat.com, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH 13/19] virtio_ring: introduce virtqueue ops Message-ID: <20250514091029-mutt-send-email-mst@kernel.org> References: <20250324054333.1954-1-jasowang@redhat.com> <20250324060127.2358-1-jasowang@redhat.com> <20250407041729-mutt-send-email-mst@kernel.org> <20250408073317-mutt-send-email-mst@kernel.org> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 0JRHz4rMKfCAK9Q9kVJIjgfmQL_e7DBKRfplhxhSlgs_1747232346 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit On Wed, Apr 09, 2025 at 12:06:03PM +0800, Jason Wang wrote: > On Tue, Apr 8, 2025 at 7:37 PM Michael S. Tsirkin wrote: > > > > On Tue, Apr 08, 2025 at 03:02:35PM +0800, Jason Wang wrote: > > > On Mon, Apr 7, 2025 at 4:20 PM Michael S. Tsirkin wrote: > > > > > > > > On Mon, Mar 24, 2025 at 02:01:21PM +0800, Jason Wang wrote: > > > > > This patch introduces virtqueue ops which is a set of the callbacks > > > > > that will be called for different queue layout or features. This would > > > > > help to avoid branches for split/packed and will ease the future > > > > > implementation like in order. > > > > > > > > > > Signed-off-by: Jason Wang > > > > > > > > > > > > > > > > > > > > > --- > > > > > drivers/virtio/virtio_ring.c | 96 +++++++++++++++++++++++++----------- > > > > > 1 file changed, 67 insertions(+), 29 deletions(-) > > > > > > > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > > > > index a2884eae14d9..ce1dc90ee89d 100644 > > > > > --- a/drivers/virtio/virtio_ring.c > > > > > +++ b/drivers/virtio/virtio_ring.c > > > > > @@ -159,9 +159,30 @@ struct vring_virtqueue_packed { > > > > > size_t event_size_in_bytes; > > > > > }; > > > > > > > > > > +struct vring_virtqueue; > > > > > + > > > > > +struct virtqueue_ops { > > > > > + int (*add)(struct vring_virtqueue *_vq, struct scatterlist *sgs[], > > > > > + unsigned int total_sg, unsigned int out_sgs, > > > > > + unsigned int in_sgs, void *data, > > > > > + void *ctx, bool premapped, gfp_t gfp); > > > > > + void *(*get)(struct vring_virtqueue *vq, unsigned int *len, void **ctx); > > > > > + bool (*kick_prepare)(struct vring_virtqueue *vq); > > > > > + void (*disable_cb)(struct vring_virtqueue *vq); > > > > > + bool (*enable_cb_delayed)(struct vring_virtqueue *vq); > > > > > + unsigned int (*enable_cb_prepare)(struct vring_virtqueue *vq); > > > > > + bool (*poll)(const struct vring_virtqueue *vq, u16 last_used_idx); > > > > > + void *(*detach_unused_buf)(struct vring_virtqueue *vq); > > > > > + bool (*more_used)(const struct vring_virtqueue *vq); > > > > > + int (*resize)(struct vring_virtqueue *vq, u32 num); > > > > > + void (*reset)(struct vring_virtqueue *vq); > > > > > +}; > > > > > > > > I like it that it's organized but > > > > I worry about the overhead of indirect calls here. > > > > > > We can switch to use INDIRECT_CALL_X() here > > > > If you think it's cleaner.. but INDIRECT_CALL is all chained > > Yes, and it would be problematic as the number of ops increased. > > > while a switch can do a binary search. > > > > Do you mean a nested switch? Not sure what is nested. gcc does a decent job of optimizing switches. You have 4 types of ops: packed/packed in order/split/split in order So: enum { VQ_SPLIT, VQ_SPLIT_IN_ORDER, VQ_PACKED, VQ_PACKED_IN_ORDER, } I do not see how it is worse? > > > > > (but I'm not sure we > > > should worry about it too much as ndo_ops or qdiscs doesn't use that). > > > > > > And that's why we ended up with xdp, no? the stack's too heavy ... > > > > > > How about a switch statement instead? > > > > > > > > struct vring_virtqueue { > > > > enum vring_virtqueue_ops ops; > > > > > > > > } > > > > > > > > > > > > @@ -2248,10 +2303,8 @@ static inline int virtqueue_add(struct virtqueue *_vq, > > > > { > > > > struct vring_virtqueue *vq = to_vvq(_vq); > > > > > > > > switch (vq->ops) { > > > > VQ_PACKED: > > > > VQ_SPLIT: > > > > VQ_IN_ORDER: > > > > } > > > > > > > > > > > > } > > > > > > > > > > > > What do you think? > > > > > > Actually, the matrix will be 2*2: > > > > > > PACKED, SPLIT, PACKED_IN_ORDER, SPLIT_IN_ORDER > > > > Confused. Same amount of enums as ops structures in your approach, no? > > I meant in this series, we will have 4 ops not 3. > > > > > > > > And will be doubled if a new layout is implemented. > > > > > > If we open them such a switch will spread in a lot of places in the code. > > > > > > Thanks > > Thanks > > > > > > > > > > > > > > > > > > > > > + > > > > > struct vring_virtqueue { > > > > > struct virtqueue vq; > > > > > > > > > > + struct virtqueue_ops *ops; > > > > > + > > > > > /* Is this a packed ring? */ > > > > > bool packed_ring; > > > > > > > > > > @@ -1116,6 +1137,8 @@ static int vring_alloc_queue_split(struct vring_virtqueue_split *vring_split, > > > > > return 0; > > > > > } > > > > > > > > > > +struct virtqueue_ops split_ops; > > > > > + > > > > > static struct virtqueue *__vring_new_virtqueue_split(unsigned int index, > > > > > struct vring_virtqueue_split *vring_split, > > > > > struct virtio_device *vdev, > > > > > @@ -1134,6 +1157,7 @@ static struct virtqueue *__vring_new_virtqueue_split(unsigned int index, > > > > > return NULL; > > > > > > > > > > vq->packed_ring = false; > > > > > + vq->ops = &split_ops; > > > > > vq->vq.callback = callback; > > > > > vq->vq.vdev = vdev; > > > > > vq->vq.name = name; > > > > > @@ -2076,6 +2100,8 @@ static void virtqueue_reset_packed(struct vring_virtqueue *vq) > > > > > virtqueue_vring_init_packed(&vq->packed, !!vq->vq.callback); > > > > > } > > > > > > > > > > +struct virtqueue_ops packed_ops; > > > > > + > > > > > static struct virtqueue *__vring_new_virtqueue_packed(unsigned int index, > > > > > struct vring_virtqueue_packed *vring_packed, > > > > > struct virtio_device *vdev, > > > > > @@ -2107,6 +2133,7 @@ static struct virtqueue *__vring_new_virtqueue_packed(unsigned int index, > > > > > vq->broken = false; > > > > > #endif > > > > > vq->packed_ring = true; > > > > > + vq->ops = &packed_ops; > > > > > vq->dma_dev = dma_dev; > > > > > vq->use_dma_api = vring_use_dma_api(vdev); > > > > > > > > > > @@ -2194,6 +2221,34 @@ static int virtqueue_resize_packed(struct vring_virtqueue *vq, u32 num) > > > > > return -ENOMEM; > > > > > } > > > > > > > > > > +struct virtqueue_ops split_ops = { > > > > > + .add = virtqueue_add_split, > > > > > + .get = virtqueue_get_buf_ctx_split, > > > > > + .kick_prepare = virtqueue_kick_prepare_split, > > > > > + .disable_cb = virtqueue_disable_cb_split, > > > > > + .enable_cb_delayed = virtqueue_enable_cb_delayed_split, > > > > > + .enable_cb_prepare = virtqueue_enable_cb_prepare_split, > > > > > + .poll = virtqueue_poll_split, > > > > > + .detach_unused_buf = virtqueue_detach_unused_buf_split, > > > > > + .more_used = more_used_split, > > > > > + .resize = virtqueue_resize_split, > > > > > + .reset = virtqueue_reset_split, > > > > > +}; > > > > > + > > > > > +struct virtqueue_ops packed_ops = { > > > > > + .add = virtqueue_add_packed, > > > > > + .get = virtqueue_get_buf_ctx_packed, > > > > > + .kick_prepare = virtqueue_kick_prepare_packed, > > > > > + .disable_cb = virtqueue_disable_cb_packed, > > > > > + .enable_cb_delayed = virtqueue_enable_cb_delayed_packed, > > > > > + .enable_cb_prepare = virtqueue_enable_cb_prepare_packed, > > > > > + .poll = virtqueue_poll_packed, > > > > > + .detach_unused_buf = virtqueue_detach_unused_buf_packed, > > > > > + .more_used = more_used_packed, > > > > > + .resize = virtqueue_resize_packed, > > > > > + .reset = virtqueue_reset_packed, > > > > > +}; > > > > > + > > > > > static int virtqueue_disable_and_recycle(struct virtqueue *_vq, > > > > > void (*recycle)(struct virtqueue *vq, void *buf)) > > > > > { > > > > > @@ -2248,10 +2303,8 @@ static inline int virtqueue_add(struct virtqueue *_vq, > > > > > { > > > > > struct vring_virtqueue *vq = to_vvq(_vq); > > > > > > > > > > - return vq->packed_ring ? virtqueue_add_packed(vq, sgs, total_sg, > > > > > - out_sgs, in_sgs, data, ctx, premapped, gfp) : > > > > > - virtqueue_add_split(vq, sgs, total_sg, > > > > > - out_sgs, in_sgs, data, ctx, premapped, gfp); > > > > > + return vq->ops->add(vq, sgs, total_sg, > > > > > + out_sgs, in_sgs, data, ctx, premapped, gfp); > > > > > } > > > > > > > > > > /** > > > > > @@ -2437,8 +2490,7 @@ bool virtqueue_kick_prepare(struct virtqueue *_vq) > > > > > { > > > > > struct vring_virtqueue *vq = to_vvq(_vq); > > > > > > > > > > - return vq->packed_ring ? virtqueue_kick_prepare_packed(vq) : > > > > > - virtqueue_kick_prepare_split(vq); > > > > > + return vq->ops->kick_prepare(vq); > > > > > } > > > > > EXPORT_SYMBOL_GPL(virtqueue_kick_prepare); > > > > > > > > > > @@ -2508,8 +2560,7 @@ void *virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len, > > > > > { > > > > > struct vring_virtqueue *vq = to_vvq(_vq); > > > > > > > > > > - return vq->packed_ring ? virtqueue_get_buf_ctx_packed(vq, len, ctx) : > > > > > - virtqueue_get_buf_ctx_split(vq, len, ctx); > > > > > + return vq->ops->get(vq, len, ctx); > > > > > } > > > > > EXPORT_SYMBOL_GPL(virtqueue_get_buf_ctx); > > > > > > > > > > @@ -2531,10 +2582,7 @@ void virtqueue_disable_cb(struct virtqueue *_vq) > > > > > { > > > > > struct vring_virtqueue *vq = to_vvq(_vq); > > > > > > > > > > - if (vq->packed_ring) > > > > > - virtqueue_disable_cb_packed(vq); > > > > > - else > > > > > - virtqueue_disable_cb_split(vq); > > > > > + return vq->ops->disable_cb(vq); > > > > > } > > > > > EXPORT_SYMBOL_GPL(virtqueue_disable_cb); > > > > > > > > > > @@ -2557,8 +2605,7 @@ unsigned int virtqueue_enable_cb_prepare(struct virtqueue *_vq) > > > > > if (vq->event_triggered) > > > > > vq->event_triggered = false; > > > > > > > > > > - return vq->packed_ring ? virtqueue_enable_cb_prepare_packed(vq) : > > > > > - virtqueue_enable_cb_prepare_split(vq); > > > > > + return vq->ops->enable_cb_prepare(vq); > > > > > } > > > > > EXPORT_SYMBOL_GPL(virtqueue_enable_cb_prepare); > > > > > > > > > > @@ -2579,8 +2626,7 @@ bool virtqueue_poll(struct virtqueue *_vq, unsigned int last_used_idx) > > > > > return false; > > > > > > > > > > virtio_mb(vq->weak_barriers); > > > > > - return vq->packed_ring ? virtqueue_poll_packed(vq, last_used_idx) : > > > > > - virtqueue_poll_split(vq, last_used_idx); > > > > > + return vq->ops->poll(vq, last_used_idx); > > > > > } > > > > > EXPORT_SYMBOL_GPL(virtqueue_poll); > > > > > > > > > > @@ -2623,8 +2669,7 @@ bool virtqueue_enable_cb_delayed(struct virtqueue *_vq) > > > > > if (vq->event_triggered) > > > > > vq->event_triggered = false; > > > > > > > > > > - return vq->packed_ring ? virtqueue_enable_cb_delayed_packed(vq) : > > > > > - virtqueue_enable_cb_delayed_split(vq); > > > > > + return vq->ops->enable_cb_delayed(vq); > > > > > } > > > > > EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed); > > > > > > > > > > @@ -2640,14 +2685,13 @@ void *virtqueue_detach_unused_buf(struct virtqueue *_vq) > > > > > { > > > > > struct vring_virtqueue *vq = to_vvq(_vq); > > > > > > > > > > - return vq->packed_ring ? virtqueue_detach_unused_buf_packed(vq) : > > > > > - virtqueue_detach_unused_buf_split(vq); > > > > > + return vq->ops->detach_unused_buf(vq); > > > > > } > > > > > EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf); > > > > > > > > > > static inline bool more_used(const struct vring_virtqueue *vq) > > > > > { > > > > > - return vq->packed_ring ? more_used_packed(vq) : more_used_split(vq); > > > > > + return vq->ops->more_used(vq); > > > > > } > > > > > > > > > > /** > > > > > @@ -2785,10 +2829,7 @@ int virtqueue_resize(struct virtqueue *_vq, u32 num, > > > > > if (recycle_done) > > > > > recycle_done(_vq); > > > > > > > > > > - if (vq->packed_ring) > > > > > - err = virtqueue_resize_packed(vq, num); > > > > > - else > > > > > - err = virtqueue_resize_split(vq, num); > > > > > + err = vq->ops->resize(vq, num); > > > > > > > > > > return virtqueue_enable_after_reset(_vq); > > > > > } > > > > > @@ -2822,10 +2863,7 @@ int virtqueue_reset(struct virtqueue *_vq, > > > > > if (recycle_done) > > > > > recycle_done(_vq); > > > > > > > > > > - if (vq->packed_ring) > > > > > - virtqueue_reset_packed(vq); > > > > > - else > > > > > - virtqueue_reset_split(vq); > > > > > + vq->ops->reset(vq); > > > > > > > > > > return virtqueue_enable_after_reset(_vq); > > > > > } > > > > > -- > > > > > 2.42.0 > > > > > >