From patchwork Tue Jan 9 01:14:51 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mina Almasry X-Patchwork-Id: 13514227 X-Patchwork-Delegate: kuba@kernel.org Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (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 E864B1391 for ; Tue, 9 Jan 2024 01:15:00 +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="KxrhJOEC" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-dbed375def6so3127086276.0 for ; Mon, 08 Jan 2024 17:15:00 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1704762900; x=1705367700; 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=iiR5N2IDxIjhT8/ImfsmGNpE4EHm5swVTh/rfapPQuI=; b=KxrhJOECZVq0swda5+Awr1AC+TOrrHUgwnHAmKXYyPk1IpO4I4qda3IisDOwDaVNlj 0YNJ2iD5w7uN/kyOB8r0P7ePgADInBANgbvaoIFr8qcgs2s10ciq+06x4pZmVS6vVN45 QpBvYjZ0Km6rD4Zs8umqodFSPJ/JMB0Gw2lw3nWGDJ7jc6M/4HNXw5c6AJc/3zcX/gSF w5uJyBmKspQL2qLc2Y9nE1jcztfoaZIK5YPl00GR8qGJQzz4KbqDG8iTXy5JyGVckbKp J06uplp/yiXJWBQKttJ/F5cQHujoh3Ik++CZMymVmVo0obZTPZQg/FKTpPkoeBFQt2nw FqQQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704762900; x=1705367700; 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=iiR5N2IDxIjhT8/ImfsmGNpE4EHm5swVTh/rfapPQuI=; b=DO7f0wXsTQwYZf/Go3cluNp04cwprLgDmAOd2AJjV7QEAEhoxsL0amhTONsX3qxaI4 qJ4Lvuus04TP0aH1pwr7vZJqhPRhGc1iD2nX/5mvFoUzgbR4ObmfqSlDvo6L1KitjZXU IMnqhMvBJmMg0UGrVlHsyWKHOoyEOw0aHrf7DbpfkZJVXjKhst7P+8qKtrmxF+1DxR6/ GzG4VDVlpsAZK8RHXhGgPMSK6F/2zJ+bX2T8X4fm9ogKfY1MqdIDHJdpp5AnMzaR3L8J lI/W0F1Q5LqGYQRPLYfNIcgiCT46AsdI7doRulvwU4RpfowvmckdyOrxAV+epYfBrfC9 h/yA== X-Gm-Message-State: AOJu0YyM1V2wUCoePMalJNvMNjyz1j7Wo984k+HAD7fY9fzHTbL1TgO/ DhQ80KyD6zLU9q3o7mxX5xb35fDXDIDzHm0QrLmdv4Jp X-Google-Smtp-Source: AGHT+IGxkvzCYnhf9wFca2+dp8mcCWrrMgZHuBUIw5hZRfjJeUDRtokP7+RnrrYFTOWxFU7NF8ERhEFW+QCMhpP48Q== X-Received: from almasrymina.svl.corp.google.com ([2620:15c:2c4:200:23bb:bfcc:9879:32e2]) (user=almasrymina job=sendgmr) by 2002:a25:b281:0:b0:dbd:c21f:eb89 with SMTP id k1-20020a25b281000000b00dbdc21feb89mr221517ybj.1.1704762899931; Mon, 08 Jan 2024 17:14:59 -0800 (PST) Date: Mon, 8 Jan 2024 17:14:51 -0800 In-Reply-To: <20240109011455.1061529-1-almasrymina@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240109011455.1061529-1-almasrymina@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20240109011455.1061529-2-almasrymina@google.com> Subject: [RFC PATCH net-next v5 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_K=C3=B6nig?= " , Shakeel Butt , Yunsheng Lin , Willem de Bruijn X-Patchwork-Delegate: kuba@kernel.org X-Patchwork-State: RFC 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/ netmem_ref can be pointers to different underlying memory types, and the low bits are set to indicate the memory type. Helpers are provided to convert netmem pointers to the underlying memory type (currently only struct page). In the devmem series helpers are provided so that calling code can use netmem without worrying about the underlying memory type unless absolutely necessary. Signed-off-by: Mina Almasry Reviewed-by: Shakeel Butt --- rfc v5: - RFC due to merge window. - Change to 'typedef unsigned long __bitwise netmem_ref;' - Fixed commit message (Shakeel). - Did not apply Shakeel's reviewed-by since the code changed significantly. 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..9f327d964782 --- /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 + +/** + * netmem_ref - a nonexistent type marking a reference to generic network + * memory. + * + * A netmem_ref 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 fields. + */ +typedef unsigned long __bitwise netmem_ref; + +/* This conversion fails (returns NULL) if the netmem_ref is not struct page + * backed. + * + * Currently struct page is the only possible netmem, and this helper never + * fails. + */ +static inline struct page *netmem_to_page(netmem_ref netmem) +{ + return (__force struct page *)netmem; +} + +/* Converting from page to netmem is always safe, because a page can always be + * a netmem. + */ +static inline netmem_ref page_to_netmem(struct page *page) +{ + return (__force netmem_ref)page; +} + +#endif /* _NET_NETMEM_H */