From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f193.google.com (mail-pf1-f193.google.com [209.85.210.193]) (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 2EAD23E5569 for ; Fri, 8 May 2026 14:57:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.193 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778252223; cv=none; b=el7FaYeDcNsj6C9LLqCQrUuRQOIiZvtpDTRsPax28cXffsXOm5BV8576tpPQ9+KBK7dRUCkjlcV7qjicQkOAPq/1w/h1MlBwjC5ShqqrZcGypuUp6oYkrna43pMY2enPXr6x3bcsskfj3wlGQ6OKtuZdc9SaTmMvLtDNBxy7s1c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778252223; c=relaxed/simple; bh=4/aVJnWaXKkXi45aVG/ghAkKHKmtNlgv64ubRDm3pNY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HVwo+qVNDJFXxVRpX8GBY4GQ8/zuAKsJSQq9D3OBkvYsWm0EKUmZ+ht3HCZVtikxIF57ug1WBFt0XJm8M8i1CFFaeYm6cpE2RbVJF4vJqb55+sP29oXGPmiUe4bcyof+qayjFDlH/hglvrZrNpNb/59KtMTuJ03AATLxI2p+mfA= 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=A3bMKqn/; arc=none smtp.client-ip=209.85.210.193 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="A3bMKqn/" Received: by mail-pf1-f193.google.com with SMTP id d2e1a72fcca58-82fbdd60b64so1544375b3a.3 for ; Fri, 08 May 2026 07:57:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1778252222; x=1778857022; 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=MKeh4P5RRX9HdRzyfTHqYV6PxblA4dDzAyEahLUA+Ik=; b=A3bMKqn/Gk8Irboq+VjkYR/RT3AMkP+uqrEWN1i6QzdfkjeKQeFGPEHxQOcNgVVCfb 3BHfxwMeebOqbTkfNMbfaMt3dOOPBVmScJUowDz5LrgnEGB8ZWSB0vIJPKwqzkUk+Xek bOrlfoBKysN3MkFH5GCsFBGcnSxFY1DeVT+6QWI8MmY4PAhaWQRyJY1F8lIguVJv1BYn iwUUi2jv4WoQmeH8e5HLfsPdIEzbhIzTBE+wQrRzt+RT4vM3myf2jEOZSsZ7+pkrET1x 8aa0PJk9TPozZc9utIvBCoaExaFcJieMoMI/sY4H1CgAacVTRrL9XW0vdmBUeAfVOzco /pww== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778252222; x=1778857022; 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=MKeh4P5RRX9HdRzyfTHqYV6PxblA4dDzAyEahLUA+Ik=; b=rjItymyfMzjM2iyHWa93mPqgBS9/0gXCMBuWwUMHYhObzMGjeYrQORqPjObl8otVda 3lvKsoBF/KgQocBmU/c8a6ZLCGub4GDpivvXxMjdoyM6s4gVRwM0kqs/rkJCxWjUYltG PCmrd+BMpQ4xe3reF+2JTf92wcg1UOnY+9KWHzB531LOElh/t9zG7O79csC0KN65vc/Y bViyiZUIv+nFn4NnXRT3qDcDjyHjEAS2QeNYWbj7xe7QWvOG/MDMNVZG40zCyxP/xcCG 5OyEeAfTVB3uGaHvTirYwQFEPCvVaEBW+MKZsPOoYE6I+1iTp/0gPGe6unSRe49iLJbu n+Rw== X-Forwarded-Encrypted: i=1; AFNElJ8tI9vyXqx43Ss9CHp2hVYIsJswKnCtDQ7HeXzsxorwArf27t8hdX4ILjpDCKATIgwXbNF359YUp6E=@vger.kernel.org X-Gm-Message-State: AOJu0YxtzeDNkRD8/yiIgtvEm/nJAjSf0snFcDGaTyz/OMm6WpNoq8YU SVOyKJRkhYgn0k0y/SAAS+QbAjnpTHXubscCIk3nBFsItVuJF8c5A7Tb X-Gm-Gg: Acq92OHNmpnULID77vi7lvgRCzOqQhZpRv0Dldd0G30TijGLlvMSC0Lz75mehU36uDm 8JEF9T8qXQJoXi44dLI1WKWnC5p7PR9N5Gm2850VjUF5COwVeccVCT42LV7lmiMteSLNRvnWTWI Og99KRiyRSjGPfWr/aBedWW/g+8LxwXcwJO8Btq3TbTeiQ4/86VYNL9z7xbjWLaNrnpL6462VDh U2P+NccVNWj1mfHUwvUCbZz71w3httQqISbh9ykyH3L8uejeww/jfqXK/rm1U+7wfNMxaxAW1SD QXr1bKPDuAJ+p/xf6xcWonCPSx7YwdJ/nlwwoOy+kBO0g9f7H5tjegIxP5eKB0HrbW7L1Mkz4Fz 2WvDSFbkGUF8cve3CyOfDvaENDaPtw58tR3iyCCAe8T38pWNTA6dsx6yPiXd/NV1JdjioUH/zSI 6tiGkCJkVfY3kLKtmr X-Received: by 2002:a05:6a00:4195:b0:824:374a:1407 with SMTP id d2e1a72fcca58-83a5c4bd711mr13683272b3a.16.1778252221575; Fri, 08 May 2026 07:57:01 -0700 (PDT) Received: from localhost ([2a03:2880:2ff:72::]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-839659498f1sm16492392b3a.17.2026.05.08.07.57.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 May 2026 07:57:01 -0700 (PDT) Date: Fri, 8 May 2026 07:57:00 -0700 From: Stanislav Fomichev To: Bobby Eshleman Cc: Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , 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, 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 2/8] net: netkit: declare NETMEM_TX_NO_DMA mode Message-ID: References: <20260507-tcp-dm-netkit-v3-0-52821445867c@meta.com> <20260507-tcp-dm-netkit-v3-2-52821445867c@meta.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260507-tcp-dm-netkit-v3-2-52821445867c@meta.com> On 05/07, Bobby Eshleman wrote: > From: Bobby Eshleman > > Some virtual devices like netkit (or ifb) never DMA and never touch frag > contents, they just forward the skb to another device. They are unable > to forward unreadable skbs, however, because they fail to pass TX > validation checks on dev->netmem_tx. The existing two-state > NETMEM_TX_NONE / NETMEM_TX_DMA doesn't give the TX validator enough > information to differentiate devices that will attempt DMA on the > unreadable skb from those that will simply route it untouched. > > Add a third mode to the enum so drivers can indicate 1) if they have > netmem TX support, and 2) if they do, whether they are DMA-capable: > > NETMEM_TX_NO_DMA - pass-through, device never DMAs > > Widen dev->netmem_tx from a 1-bit field to 2 bits to fit the new value, > and declare netkit as NETMEM_TX_NO_DMA. Devmem TX support over these > devices comes in a follow-up patch. > > Signed-off-by: Bobby Eshleman Acked-by: Stanislav Fomichev