From nobody Fri Dec 26 19:25:13 2025 Received: from mail-yw1-f202.google.com (mail-yw1-f202.google.com [209.85.128.202]) (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 A990B168D2 for ; Tue, 2 Jan 2024 21:27:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--almasrymina.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="MNL4EceK" Received: by mail-yw1-f202.google.com with SMTP id 00721157ae682-5e898eb4432so132116677b3.0 for ; Tue, 02 Jan 2024 13:27:23 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1704230842; x=1704835642; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=+ua1kNBJ+w+Y3Am0MQe4kWPDeg8Cx+E0rh5th4nzq7c=; b=MNL4EceK0xE1DtiTd6UXEb+JAYB1pom/TSH9H1tgEXHrOvUweoBtJhNVXDoxkFUXom sTPXfZB4P7UweEJMp7oLfNyHlww2pRRUKZ14Sa24LAIqHszarlAanMXnP1Umg/YYvwAX /www+Dt7sUoO1uQfppmZv/3C5Q9NT0eiQLDZJEJ938scB2cueT0wF2hGF3XvFkLMgn0h mYLHMDsOz6F0wdXb0LPSVs0DV0fxrRZQLxjJEDpc85JobdJ15pJ0y7qQnJ9jR4zu0Chy YNi0YvsXvHcLvuaTkdmdODvfyoaNi5Dn0lOTbjGBWeqCpOtfg89o2Vk43jsU1T/CnuwA Yy7g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704230842; x=1704835642; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=+ua1kNBJ+w+Y3Am0MQe4kWPDeg8Cx+E0rh5th4nzq7c=; b=oaB5CGsEy8Jc5iknPKB2mhOsylnb71XEexY3wK1hCYGbMa+LeIqWRzzJ2/0sqMLJPQ CQ5chmOVh7dA4658uQme/K0KKVkkFyWZ19C17Ea+KbBvJ18MyjpgITe+ThNCYt/CDWo/ 1LHkvKnrS7UYxGWr0pzIPTHCfUzKWcRhltTfI4Jh+OIB6Ajv3vp1gCM39rIubhEF6b1o 1lp/0gJcer4SFYPQzhEcYcPi2Lc0yi5Ki2pe1ogqjyDTwQxKe/m2I0Nz3VtL+Kr411Qs +C7WkvolMnUjqyzqg7ZTMLQ1q1HfOTwM+2ii4fQgJwlk0WqFJE9DYnytF6oX+PD9wO71 93Dg== X-Gm-Message-State: AOJu0YwVeJ6jDRFU6xwbsFH7MkInyC6/h4jwUEqgmz7gUZqDC6Q4ov6T 1+m46rSBmK2N8kOFxcMoJuxAXH6rk74XKUzogkFmAZLph/m01cEQWpZiADqUhrjZ6j28goHnx/H FbA0SK/AAIF9EhDXkQ5tLuuETTJ5K7nImx1NY6NpFEJBswQYh390+14n4tuvyFnlY4wI4h7AT4g eyM1mRX7biqqUeOw== X-Google-Smtp-Source: AGHT+IFfsq9rzU5qbwwpNbrjG4PnHnpfMmz0iSjvUCZ3agkQwNiVtOi+CeRAKraq69yDp7uCH/p+XQ2tyujR5vbThQ== X-Received: from almasrymina.svl.corp.google.com ([2620:15c:2c4:200:9a04:c262:c978:d762]) (user=almasrymina job=sendgmr) by 2002:a81:4c04:0:b0:5f4:393:2a46 with SMTP id z4-20020a814c04000000b005f403932a46mr314782ywa.10.1704230842596; Tue, 02 Jan 2024 13:27:22 -0800 (PST) Date: Tue, 2 Jan 2024 13:27:14 -0800 In-Reply-To: <20240102212716.810731-1-almasrymina@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240102212716.810731-1-almasrymina@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20240102212716.810731-2-almasrymina@google.com> Subject: [RFC PATCH net-next v4 1/2] net: introduce abstraction for network memory From: Mina Almasry To: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Cc: Mina Almasry , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jason Gunthorpe , "=?UTF-8?q?Christian=20K=C3=B6nig?=" , Shakeel Butt , Yunsheng Lin , Willem de Bruijn Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add the netmem_ref type, an abstraction for network memory. To add support for new memory types to the net stack, we must first abstract the current memory type. Currently parts of the net stack use struct page directly: - page_pool - drivers - skb_frag_t Originally the plan was to reuse struct page* for the new memory types, and to set the LSB on the page* to indicate it's not really a page. However, for compiler type checking we need to introduce a new type. netmem_ref is introduced to abstract the underlying memory type. Currently it's a no-op abstraction that is always a struct page underneath. In parallel there is an undergoing effort to add support for devmem to the net stack: https://lore.kernel.org/netdev/20231208005250.2910004-1-almasrymina@google.= com/ Signed-off-by: Mina Almasry Reviewed-by: Shakeel Butt --- v4: - use 'struct netmem;' instead of 'typedef void *__bitwise netmem_ref;' Using __bitwise with a non-integer type was wrong and triggered many patchwork bot errors/warnings. Using an integer type causes the compiler to warn when casting NULL to the integer type. Attempt to use an empty struct for our opaque network memory. v3: - Modify struct netmem from a union of struct page + new types to an opaque netmem_ref type. I went with: +typedef void *__bitwise netmem_ref; rather than this that Jakub recommended: +typedef unsigned long __bitwise netmem_ref; Because with the latter the compiler issues warnings to cast NULL to netmem_ref. I hope that's ok. - Add some function docs. v2: - Use container_of instead of a type cast (David). --- include/net/netmem.h | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 include/net/netmem.h diff --git a/include/net/netmem.h b/include/net/netmem.h new file mode 100644 index 000000000000..d821fe0f8147 --- /dev/null +++ b/include/net/netmem.h @@ -0,0 +1,41 @@ +/* SPDX-License-Identifier: GPL-2.0 + * + * Network memory + * + * Author: Mina Almasry + */ + +#ifndef _NET_NETMEM_H +#define _NET_NETMEM_H + +/** + * struct netmem - a nonexistent type marking a reference to generic netwo= rk + * memory. + * + * A struct netmem* currently is always a reference to a struct page. This + * abstraction is introduced so support for new memory types can be added. + * + * Use the supplied helpers to obtain the underlying memory pointer and fi= elds. + */ +struct netmem; + +/* This conversion fails (returns NULL) if the struct netmem* is not struc= t page + * backed. + * + * Currently struct page is the only possible netmem, and this helper never + * fails. + */ +static inline struct page *netmem_to_page(struct netmem *netmem) +{ + return (struct page *)netmem; +} + +/* Converting from page to netmem is always safe, because a page can alway= s be + * a netmem. + */ +static inline struct netmem *page_to_netmem(struct page *page) +{ + return (struct netmem *)page; +} + +#endif /* _NET_NETMEM_H */ --=20 2.43.0.472.g3155946c3a-goog