From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qk1-f169.google.com (mail-qk1-f169.google.com [209.85.222.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 04E7B14EC62 for ; Wed, 26 Feb 2025 20:27:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.169 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740601670; cv=none; b=hyls8TKu87+wZcHIyqyDk4cKzmAS9fXuYBApcv3us6olZldEDGFfoAkvhXgz2kJ2aqwKA+ABW8vcmFz4XqIIdxUt++jHJtVQ9DRWev0sb0+QFKp5jieLnbP+4kqLXKjIH8WVFSjIO6kP5dsmHFPXDE0ybjvYuHTJfzuZLtWgcZw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740601670; c=relaxed/simple; bh=k+QDB4VYH0R9a9+nYzNmvEIhcYQPChkqjyD9WG2Hmh4=; h=Date:From:To:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=AV5ZafogjQhniKmwHl7M5uFpXreewU++BwXByYy4JcEcrcHPZ3+KYryzEPEQ8mcURuNQCH6NeZhRjx2MDf3xgQIQZp3M9tYqQVApyZgYYkz/p15rwdOcnVQNmGlyTj5IZ8RVqrrcGokHgxgvwv7OU74572JVTHbg5EqhUWkm/58= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=fastly.com; spf=pass smtp.mailfrom=fastly.com; dkim=pass (1024-bit key) header.d=fastly.com header.i=@fastly.com header.b=MrWdNX+c; arc=none smtp.client-ip=209.85.222.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=fastly.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=fastly.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=fastly.com header.i=@fastly.com header.b="MrWdNX+c" Received: by mail-qk1-f169.google.com with SMTP id af79cd13be357-7c0818add57so17701185a.3 for ; Wed, 26 Feb 2025 12:27:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fastly.com; s=google; t=1740601666; x=1741206466; darn=vger.kernel.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:mail-followup-to:message-id:subject:to:from :date:from:to:cc:subject:date:message-id:reply-to; bh=ySARA6axU/KgaQ0dVNI+ZmJXsucfopJX3wr+2O18FBA=; b=MrWdNX+cw7UFZmA2YF8kovMhfBr4sxn+gVbUVUxS1CskzY2DR0/IcFHQxXtnHTdFZZ ubfidBHMMDrgNgGLXbhhSvKaHdwLxKLAY3MV5TEolhGFHAU1BSLTnMF/sicX8uDc+ehw ysG5km+mjtLYIpESxnYaB939bh2ninAOSm5J0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740601666; x=1741206466; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:mail-followup-to:message-id:subject:to:from :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=ySARA6axU/KgaQ0dVNI+ZmJXsucfopJX3wr+2O18FBA=; b=BJnF52OaMUfRi4d290IoPU8r+ZrH8geVYpTdbREevoSHIOi+AjdsEfNB3vHjkaaT0Z 2H8UUvG2S5MhFFCQG1RLaCwGFr4oBuupD6WEWUhWddjaM0GB/CIQlS3KkH9MwHSjitFD FHXvFadwwt0XkTPkjRWW9UPxQE7YgVSGT25m59vWvuMbg1pFA6NT4yqrJAEYLc9mfF6S yQYLlGXBeGZKM3vs5+h1kPa65Jd7VaHG67WSCOHM18Mq6KuvK/JLRb0vZyX5bbxyJjA2 ey53hVjBkvmPycLMI6QEUAW4NC2aKLaCqMsMwf116jXhctQlmx4DbpnJj+5nLXeEwuNW dawg== X-Forwarded-Encrypted: i=1; AJvYcCXFwX6zfANkO/dCVOxWAAmjHS+Y26qga6h1hrLJVPPNO5aCbAccNnHUUCnNXq2g4U5Gl9KGoaRH13iWW4s=@vger.kernel.org X-Gm-Message-State: AOJu0Yx0sL4xYkWxnlpmvAn4e4mzrcKz0uAtVj6d+E65g9FW50Z4G/+6 B7kR5wyLIuOLVCo+cbahdpAc/VMO7XZTZ1gZAy4AdLBQoq82CcbCK3qXERskMWM= X-Gm-Gg: ASbGncuEycm0FXelS/2ayA4NfeRKjqMLgGOtUQWO2K5Mk+jdKY0AtgYXRHwwsNv0cDf m5jSpG44/6roSbb1mUqSvlswRlk7KBXweG5avoBbCkUE2CrvgpYPMG0agHeRZROckuVZ5XmmmPb LioUbCcOYGrSDsbJ7XHAu3peKbcCS+6jtrFNHuXDf8ZbXZdAoHRTfKtsAYCJjMAhlirc4A/I7Fi U8BmEHSE6714Bk5chi4PNVgMAxCRvRlWORR6cESE71qNCPT/Qse6d8KPesa2JEbxeG2InfBg1jg lndnjDb5bbTxNTozVL/p0tSgJEXOG+BAWNuTCXC8/zcF2m7bhVpU6Mp2YhLNP8Fa X-Google-Smtp-Source: AGHT+IEv7viTJhM0Js6vvlYUnBH9P9HF8SbdCpdZLNRgMY6wPWIHhpmuyL0yIEE3uUMtvehXKZHFUA== X-Received: by 2002:a05:620a:4415:b0:7c0:c0e0:8beb with SMTP id af79cd13be357-7c0cf96e406mr2798739585a.57.1740601665863; Wed, 26 Feb 2025 12:27:45 -0800 (PST) Received: from LQ3V64L9R2 (ool-44c5a22e.dyn.optonline.net. [68.197.162.46]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c23c33f3ddsm292586885a.93.2025.02.26.12.27.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Feb 2025 12:27:45 -0800 (PST) Date: Wed, 26 Feb 2025 15:27:42 -0500 From: Joe Damato To: Jason Wang , netdev@vger.kernel.org, mkarsten@uwaterloo.ca, gerhard@engleder-embedded.com, xuanzhuo@linux.alibaba.com, kuba@kernel.org, "Michael S. Tsirkin" , Eugenio =?iso-8859-1?Q?P=E9rez?= , Andrew Lunn , "David S. Miller" , Eric Dumazet , Paolo Abeni , "open list:VIRTIO CORE AND NET DRIVERS" , open list Subject: Re: [PATCH net-next v4 3/4] virtio-net: Map NAPIs to queues Message-ID: Mail-Followup-To: Joe Damato , Jason Wang , netdev@vger.kernel.org, mkarsten@uwaterloo.ca, gerhard@engleder-embedded.com, xuanzhuo@linux.alibaba.com, kuba@kernel.org, "Michael S. Tsirkin" , Eugenio =?iso-8859-1?Q?P=E9rez?= , Andrew Lunn , "David S. Miller" , Eric Dumazet , Paolo Abeni , "open list:VIRTIO CORE AND NET DRIVERS" , open list References: <20250225020455.212895-1-jdamato@fastly.com> <20250225020455.212895-4-jdamato@fastly.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, Feb 26, 2025 at 01:08:49PM -0500, Joe Damato wrote: > On Wed, Feb 26, 2025 at 01:03:09PM -0500, Joe Damato wrote: > > On Wed, Feb 26, 2025 at 01:48:50PM +0800, Jason Wang wrote: > > > On Tue, Feb 25, 2025 at 10:05 AM Joe Damato wrote: > > > > > > > > Use netif_queue_set_napi to map NAPIs to queue IDs so that the mapping > > > > can be accessed by user apps, taking care to hold RTNL as needed. > > > > > > I may miss something but I wonder whether letting the caller hold the > > > lock is better. > > > > Hmm... > > > > Double checking all the paths over again, here's what I see: > > - refill_work, delayed work that needs RTNL so this change seems > > right? > > > > - virtnet_disable_queue_pair, called from virtnet_open and > > virtnet_close. When called via NDO these are safe and hold RTNL, > > but they can be called from power management and need RTNL. > > > > - virtnet_enable_queue_pair called from virtnet_open, safe when > > used via NDO but needs RTNL when used via power management. > > > > - virtnet_rx_pause called in both paths as you mentioned, one > > which needs RTNL and one which doesn't. > > Sorry, I missed more paths: > > - virtnet_rx_resume > - virtnet_tx_pause and virtnet_tx_resume > > which are similar to path you mentioned (virtnet_rx_pause) and need > rtnl in one of two different paths. > > Let me know if I missed any paths and what your preferred way to fix > this would be? > > I think both options below are possible and I have no strong > preference. OK, my apologies. I read your message and the code wrong. Sorry for the back-to-back emails from me. Please ignore my message above... I think after re-reading the code, here's where I've arrived: - refill_work needs to hold RTNL (as in the existing patch) - virtnet_rx_pause, virtnet_rx_resume, virtnet_tx_pause, virtnet_tx_resume -- all do NOT need to hold RTNL because it is already held in the ethtool resize path and the XSK path, as you explained, but I mis-read (sorry). - virtnet_disable_queue_pair and virtnet_enable_queue_pair both need to hold RTNL only when called via power management, but not when called via ndo_open or ndo_close Is my understanding correct and does it match your understanding? If so, that means there are two issues: 1. Fixing the hardcoded bools in rx_pause, rx_resume, tx_pause, tx_resume (all should be false, RTNL is not needed). 2. Handling the power management case which calls virtnet_open and virtnet_close. I made a small diff included below as an example of a possible solution: 1. Modify virtnet_disable_queue_pair and virtnet_enable_queue_pair to take a "bool need_rtnl" and pass it through to the helpers they call. 2. Create two helpers, virtnet_do_open and virt_do_close both of which take struct net_device *dev, bool need_rtnl. virtnet_open and virtnet_close are modified to call the helpers and pass false for need_rtnl. The power management paths call the helpers and pass true for need_rtnl. (fixes issue 2 above) 3. Fix the bools for rx_pause, rx_resume, tx_pause, tx_resume to pass false since all paths that I could find that lead to these functions hold RTNL. (fixes issue 1 above) See the diff below (which can be applied on top of patch 3) to see what it looks like. If you are OK with this approach, I will send a v5 where patch 3 includes the changes shown in this diff. Please let me know what you think: diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 13bb4a563073..76ecb8f3ce9a 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -3098,14 +3098,16 @@ static int virtnet_poll(struct napi_struct *napi, int budget) return received; } -static void virtnet_disable_queue_pair(struct virtnet_info *vi, int qp_index) +static void virtnet_disable_queue_pair(struct virtnet_info *vi, int qp_index, + bool need_rtnl) { - virtnet_napi_tx_disable(&vi->sq[qp_index], false); - virtnet_napi_disable(&vi->rq[qp_index], false); + virtnet_napi_tx_disable(&vi->sq[qp_index], need_rtnl); + virtnet_napi_disable(&vi->rq[qp_index], need_rtnl); xdp_rxq_info_unreg(&vi->rq[qp_index].xdp_rxq); } -static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index) +static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index, + bool need_rtnl) { struct net_device *dev = vi->dev; int err; @@ -3120,8 +3122,8 @@ static int virtnet_enable_queue_pair(struct virtnet_info *vi, int qp_index) if (err < 0) goto err_xdp_reg_mem_model; - virtnet_napi_enable(&vi->rq[qp_index], false); - virtnet_napi_tx_enable(&vi->sq[qp_index], false); + virtnet_napi_enable(&vi->rq[qp_index], need_rtnl); + virtnet_napi_tx_enable(&vi->sq[qp_index], need_rtnl); return 0; @@ -3156,7 +3158,7 @@ static void virtnet_update_settings(struct virtnet_info *vi) vi->duplex = duplex; } -static int virtnet_open(struct net_device *dev) +static int virtnet_do_open(struct net_device *dev, bool need_rtnl) { struct virtnet_info *vi = netdev_priv(dev); int i, err; @@ -3169,7 +3171,7 @@ static int virtnet_open(struct net_device *dev) if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL)) schedule_delayed_work(&vi->refill, 0); - err = virtnet_enable_queue_pair(vi, i); + err = virtnet_enable_queue_pair(vi, i, need_rtnl); if (err < 0) goto err_enable_qp; } @@ -3190,13 +3192,18 @@ static int virtnet_open(struct net_device *dev) cancel_delayed_work_sync(&vi->refill); for (i--; i >= 0; i--) { - virtnet_disable_queue_pair(vi, i); + virtnet_disable_queue_pair(vi, i, need_rtnl); virtnet_cancel_dim(vi, &vi->rq[i].dim); } return err; } +static int virtnet_open(struct net_device *dev) +{ + return virtnet_do_open(dev, false); +} + static int virtnet_poll_tx(struct napi_struct *napi, int budget) { struct send_queue *sq = container_of(napi, struct send_queue, napi); @@ -3373,7 +3380,7 @@ static void virtnet_rx_pause(struct virtnet_info *vi, struct receive_queue *rq) bool running = netif_running(vi->dev); if (running) { - virtnet_napi_disable(rq, true); + virtnet_napi_disable(rq, false); virtnet_cancel_dim(vi, &rq->dim); } } @@ -3386,7 +3393,7 @@ static void virtnet_rx_resume(struct virtnet_info *vi, struct receive_queue *rq) schedule_delayed_work(&vi->refill, 0); if (running) - virtnet_napi_enable(rq, true); + virtnet_napi_enable(rq, false); } static int virtnet_rx_resize(struct virtnet_info *vi, @@ -3415,7 +3422,7 @@ static void virtnet_tx_pause(struct virtnet_info *vi, struct send_queue *sq) qindex = sq - vi->sq; if (running) - virtnet_napi_tx_disable(sq, true); + virtnet_napi_tx_disable(sq, false); txq = netdev_get_tx_queue(vi->dev, qindex); @@ -3449,7 +3456,7 @@ static void virtnet_tx_resume(struct virtnet_info *vi, struct send_queue *sq) __netif_tx_unlock_bh(txq); if (running) - virtnet_napi_tx_enable(sq, true); + virtnet_napi_tx_enable(sq, false); } static int virtnet_tx_resize(struct virtnet_info *vi, struct send_queue *sq, @@ -3708,7 +3715,7 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs) return 0; } -static int virtnet_close(struct net_device *dev) +static int virtnet_do_close(struct net_device *dev, bool need_rtnl) { struct virtnet_info *vi = netdev_priv(dev); int i; @@ -3727,7 +3734,7 @@ static int virtnet_close(struct net_device *dev) cancel_work_sync(&vi->config_work); for (i = 0; i < vi->max_queue_pairs; i++) { - virtnet_disable_queue_pair(vi, i); + virtnet_disable_queue_pair(vi, i, need_rtnl); virtnet_cancel_dim(vi, &vi->rq[i].dim); } @@ -3736,6 +3743,11 @@ static int virtnet_close(struct net_device *dev) return 0; } +static int virtnet_close(struct net_device *dev) +{ + return virtnet_do_close(dev, false); +} + static void virtnet_rx_mode_work(struct work_struct *work) { struct virtnet_info *vi = @@ -5682,7 +5694,7 @@ static void virtnet_freeze_down(struct virtio_device *vdev) netif_device_detach(vi->dev); netif_tx_unlock_bh(vi->dev); if (netif_running(vi->dev)) - virtnet_close(vi->dev); + virtnet_do_close(vi->dev, true); } static int init_vqs(struct virtnet_info *vi); @@ -5702,7 +5714,7 @@ static int virtnet_restore_up(struct virtio_device *vdev) enable_rx_mode_work(vi); if (netif_running(vi->dev)) { - err = virtnet_open(vi->dev); + err = virtnet_do_open(vi->dev, false); if (err) return err; }