From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qk1-f179.google.com (mail-qk1-f179.google.com [209.85.222.179]) (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 22DA33FB7DB for ; Fri, 8 May 2026 21:29:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778275744; cv=none; b=VMPAwzmNUu2WWnGAqNbW6h5Nw9eoQIdxj+9D//QU8FNsWYAixXJiZGPgDVA6CvXRqeLc8teQJgCW4OdZ4j49JpHxK7fyARunqJVuCHPdME/Mn1i8yu5yNv2ZCxpkL/ed2TQirVFSKrnDYYePmoJIPOouEL2p83cRjghu4TYWP9s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778275744; c=relaxed/simple; bh=lm4ZsFpNUgwpK3YnX3D6FcdAELUM2A+q69wdbtD9hng=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mnoz7nn0qb8CVU+1uygdchmYls0p2BRa3Z0HQy9aYNNQAquTAU5sGFhV+0PAMyfFzF+1oP7vO24DriO3vuFbA0p+3+8kKd5C10PVsS1YSn0g6KHW7m97JqPh598Bswc7729yS2kv7kDsrnEp3H0oIAlLSqHwW7eXhFknNvgFPnM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=dB1NAApR; arc=none smtp.client-ip=209.85.222.179 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="dB1NAApR" Received: by mail-qk1-f179.google.com with SMTP id af79cd13be357-8ec37d52c0dso341057785a.0 for ; Fri, 08 May 2026 14:29:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1778275742; x=1778880542; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=/LAF18jiWTLJl8Jwx6HS2JQdllgi/a4OQyHfJwaQg84=; b=dB1NAApRVCzA/GJ3Zsj63KroNB3QF16jAEzm+2Y5Z4Jd6dJRojdXOImqLa5jsJ03kR oM/vSwYadVwGRFXbPLOt3JG+qV+ygFOV00YT6B5e4Fu20iTuJdcv+qvm9D7yn4TZQDzo 3lsUguU7SvDpNkkDK6cKzT4c2pYtv9rVlqvRF6OZqJP7pbuNfdoMwpAq4czB6xxAHT8H 917O/5/cvnid69CWTYlJ3+TNduUJxqIpCx1HHiigYYR7S3fEbAcwboEx8qCQ6cT0KwYY 6k8wF0lJVBkEO+2gBk7UV/0ivXlmvaqhu3wlQhVuzHjXvPqeqhbkQN89BOg7fu3pW1kN bUhg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778275742; x=1778880542; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=/LAF18jiWTLJl8Jwx6HS2JQdllgi/a4OQyHfJwaQg84=; b=WsoV8uhsJCUZKmmkFxvXTU0okkTZUZmPBXWBTRI7861PAcbJoKjIZbHNW1WRkts8fI eO5a8wNis8fyUCM2JfFVXEzLos+/ShbMR9sFFk4dJ0CW6VDD49xulK8V/2kLLFunB3yS wkGBs2RD4A2Nf2m1VL8cnNmjjpD46SRwmfRdMH/E9S1fOW1CisWFZCNCnUQNUGLa8BAQ 9bqfAhASB8Qukg7BlBuKNNy2SmOU9NG17F5SusHxAl9iJsic8NZ/lJbP0Ke2QP6kwVed kBMePuFXIj/0vvXJTJGEaCMiWyQH8IoQnII9dpFdmNRqpKe5XudWY3e+kdCDXQhj0Flo SZkw== X-Forwarded-Encrypted: i=1; AFNElJ/wS1+jervN09sglSXhe+NuCYDbn+SLAsOYQMzLknchb49gKTF/rAJ66BWOiCQNhHridTQf1jeUk3hGRJC9tq4=@vger.kernel.org X-Gm-Message-State: AOJu0YyLH7VNJA1akyelsD21hshFmZpv1fJCq68OcecHGkbwZFfq+n1r VxNNlT99sgHRqFPaxA3E9EGnwXQt0D29L6eWL1Lpi6KDmEJp+eFcaW2N X-Gm-Gg: AeBDiesLOvoNS61nv312E2EtzSVzmoGIzbL44YYb0uNbnZAfFuohp/hkuVuOLhSx+6c akme2C9bOyarwwboj6yRD61ypJrOSPAlFWsY9nrxanW4hIVZCFyXYNhWMUrTHk3AtYAUNGI+j4y jOqbTXRhvSorP0Fg0AH6cJelFZEnEMNGrbLUUeYDZzTu2JT5yfr8Je/x3dqwrVzy6SAG1RjpdTz +5j5Wmt8TSsGIqE0ucpXolsL4Qn3UOKUbUmDACI7nM6k8rsdrhQ7S3uLMiECdZTwJKUC6dIibt7 pXu2qLr4RmLv+2ke4SM8IkklApcye+GHBEBBBzyXhAsfz0H7/VHa/s3pHeYXlbiKgMsdJLgONZT DTQM2LiOG3R96626yWCTvVK9ozWGlR+NmxVS+d3U/TX8RLt8MOI0NOeWjmBbt+C5cz5X9qjR94y Eggn0HcRtSO0f7rYT762Rz+BLAaJa2R3i6eC+rbnvkT5Z8HzFfPFF7l1fovAzw5lYSUMw= X-Received: by 2002:a05:620a:40d0:b0:8dd:b4fc:d561 with SMTP id af79cd13be357-904d438db5dmr2198955585a.10.1778275741832; Fri, 08 May 2026 14:29:01 -0700 (PDT) Received: from devvm29614.prn0.facebook.com ([2a03:2880:f800:1::]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8fc2cd057acsm2596938185a.47.2026.05.08.14.28.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 May 2026 14:29:01 -0700 (PDT) Date: Fri, 8 May 2026 14:28:55 -0700 From: Bobby Eshleman To: Jakub Kicinski Cc: Andrew Lunn , "David S. Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , Jonathan Corbet , Shuah Khan , Alex Shi , Yanteng Si , Dongliang Mu , Michael Chan , Pavan Chebbi , Joshua Washington , Harshitha Ramamurthy , Saeed Mahameed , Tariq Toukan , Mark Bloch , Leon Romanovsky , Alexander Duyck , kernel-team@meta.com, Daniel Borkmann , Nikolay Aleksandrov , Shuah Khan , dw@davidwei.uk, sdf.kernel@gmail.com, mohsin.bashr@gmail.com, willemb@google.com, jiang.kun2@zte.com.cn, xu.xin16@zte.com.cn, wang.yaxin@zte.com.cn, netdev@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, Stanislav Fomichev , Mina Almasry , Bobby Eshleman Subject: Re: [PATCH net-next v3 3/8] net: devmem: support TX over NETMEM_TX_NO_DMA devices Message-ID: References: <20260507-tcp-dm-netkit-v3-0-52821445867c@meta.com> <20260507-tcp-dm-netkit-v3-3-52821445867c@meta.com> <20260508134717.4ef87ab6@kernel.org> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260508134717.4ef87ab6@kernel.org> On Fri, May 08, 2026 at 01:47:17PM -0700, Jakub Kicinski wrote: > On Thu, 07 May 2026 19:27:48 -0700 Bobby Eshleman wrote: > > + /* Virtual device (e.g. netkit) the user called bind-tx on. Must be > > + * NETMEM_TX_NO_DMA. > > + */ > > + struct net_device *vdev; > > AI keeps complaining that we don't hold a reference to this dev which > I think is fine, we're just comparing pointers. Could we maybe make this > a void pointer and mention in the comment that we treat it as "best > effort cookie" (better phrasing welcome). > > Or we should wipe these vdev pointers when vdevs disappear, not sure > how hard that'd be (or whether it's worth the extra state). My guess is this would probably be the simplest way? diff --git a/net/core/devmem.c b/net/core/devmem.c index 644c286b778f..e28fae14c687 100644 --- a/net/core/devmem.c +++ b/net/core/devmem.c @@ -533,3 +533,38 @@ static const struct memory_provider_ops dmabuf_devmem_ops = { .nl_fill = mp_dmabuf_devmem_nl_fill, .uninstall = mp_dmabuf_devmem_uninstall, }; + +static int net_devmem_netdev_event(struct notifier_block *nb, + unsigned long event, void *ptr) +{ + struct net_device *dev = netdev_notifier_info_to_dev(ptr); + struct net_devmem_dmabuf_binding *binding; + unsigned long id; + + if (event != NETDEV_UNREGISTER) + return NOTIFY_DONE; + + xa_for_each(&net_devmem_dmabuf_bindings, id, binding) { + if (!net_devmem_dmabuf_binding_get(binding)) + continue; + mutex_lock(&binding->lock); + if (READ_ONCE(binding->vdev) == dev) { + ASSERT_EXCLUSIVE_WRITER(binding->vdev); + WRITE_ONCE(binding->vdev, NULL); + } + mutex_unlock(&binding->lock); + net_devmem_dmabuf_binding_put(binding); + } + + return NOTIFY_DONE; +} + +static struct notifier_block net_devmem_netdev_nb = { + .notifier_call = net_devmem_netdev_event, +}; + +static int __init net_devmem_init(void) +{ + return register_netdevice_notifier(&net_devmem_netdev_nb); +} +subsys_initcall(net_devmem_init); I'm open to either approach. The void* + comment is good too, IMHO. For the notifier, I'd probably want to add a test too ensure sendmsg() kicks back after the device is removed. Best, Bobby