From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.20]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2835735B64D; Mon, 23 Mar 2026 19:25:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.20 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774293917; cv=none; b=BLV4EbXFJWRKhVGC/FhjonIifEkUS+sNsPq3HdSl+1XfBIjW3JnmIt/Lqhv6SSi5kODeKpGJt9lzKNIzt06OOSe37uI3xKYE+HDht+8zIMh1Xnb8YFFDUO1zad+VOke6K84axx/WlQA7RVQWxviYrv/x7xfCfY5j4dYuul1G0aI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774293917; c=relaxed/simple; bh=PzBFdDhMquFEuDQF9TQj8dLh3ssgnCZMs5ANL6V0d74=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=WD/nAL8pBE8L+GNyQ3605hh8583EDxihgAfinCYaeGZoN5PgpdwAtRhpmAovlJz2pHdcmX6ENgcjsJMHFmL9iSr8a/wBaLmXnw5x0p+qWYA+y6OiMft0H9pZ7dC322efzC/qqd4JYS965mjweZ2pNALvBXA6W7oQhSoRmMsFdnc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=JqVOmgsO; arc=none smtp.client-ip=198.175.65.20 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="JqVOmgsO" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1774293917; x=1805829917; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=PzBFdDhMquFEuDQF9TQj8dLh3ssgnCZMs5ANL6V0d74=; b=JqVOmgsOvai/BgjN/SusTq7jwRTuy03Fjf8s9kHN+SfuDsBeicZHVCBi GL7MXyaZ5t9XaSZhCH1amhm33G6NXKIg5WTDErOtEAm2Y+o2Oij8gM4lj H/KDdyq9Pyem/upHKT58mFx9dc9Md01Lf7HJXHFa5horccmzH7SXLSsUg A+uUcTQ9M9e74+gNBfmIlc81ZCfM/nUQXJ61EcPH2lfkqN7PHNaEQO2c7 sIPz91KarZmMHjENYqX5Nr3aHnfBNFnIpOOozC7VosNGOTHv0DFNkAVXV VCMCLp1hjppoZIOM5imUrSWkSIyDr9ex4/ofuGnw4zEQLj6KolkgzJLP8 A==; X-CSE-ConnectionGUID: /yZygYPZQLebtvXY96+VqA== X-CSE-MsgGUID: AFkuf6bkTlmQ6vU8cZLA5w== X-IronPort-AV: E=McAfee;i="6800,10657,11738"; a="75013317" X-IronPort-AV: E=Sophos;i="6.23,137,1770624000"; d="scan'208";a="75013317" Received: from orviesa003.jf.intel.com ([10.64.159.143]) by orvoesa112.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Mar 2026 12:25:16 -0700 X-CSE-ConnectionGUID: CHs6XnMgRCeSAxnBqS5oJA== X-CSE-MsgGUID: hNRiaATlQMywvFNhrSONIg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,137,1770624000"; d="scan'208";a="228187880" Received: from boxer.igk.intel.com ([10.102.20.173]) by orviesa003.jf.intel.com with ESMTP; 23 Mar 2026 12:25:13 -0700 From: Maciej Fijalkowski To: netdev@vger.kernel.org Cc: bpf@vger.kernel.org, magnus.karlsson@intel.com, stfomichev@gmail.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, larysa.zaremba@intel.com, aleksander.lobakin@intel.com, bjorn@kernel.org, Maciej Fijalkowski , Stanislav Fomichev Subject: [PATCH v3 net 2/8] xsk: respect tailroom for ZC setups Date: Mon, 23 Mar 2026 20:24:51 +0100 Message-Id: <20260323192457.504631-3-maciej.fijalkowski@intel.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20260323192457.504631-1-maciej.fijalkowski@intel.com> References: <20260323192457.504631-1-maciej.fijalkowski@intel.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Multi-buffer XDP stores information about frags in skb_shared_info that sits at the tailroom of a packet. The storage space is reserved via xdp_data_hard_end(): ((xdp)->data_hard_start + (xdp)->frame_sz - \ SKB_DATA_ALIGN(sizeof(struct skb_shared_info))) and then we refer to it via macro below: static inline struct skb_shared_info * xdp_get_shared_info_from_buff(const struct xdp_buff *xdp) { return (struct skb_shared_info *)xdp_data_hard_end(xdp); } Currently we do not respect this tailroom space in multi-buffer AF_XDP ZC scenario. To address this, introduce xsk_pool_get_tailroom() and use it within xsk_pool_get_rx_frame_size() which is used in ZC drivers to configure length of HW Rx buffer. xsk_pool_get_tailroom() is only reserving necessary space when pool is zc and underlying netdev supports zc multi-buffer. Rely on pool->dev state when configuring tailroom. xsk_pool_get_rx_frame_size() inside ndo_bpf is usually called when bringing up queues and before xsk's dma mappings have been configured, which makes it valid to rely on pool->dev. Typically drivers on Rx Hw buffers side work on 128 byte alignment so let us align the value returned by xsk_pool_get_rx_frame_size() in order to avoid addressing this on driver's side. This addresses the fact that idpf uses mentioned function *before* pool->dev being set so we were at risk that after subtracting tailroom we would not provide 128-byte aligned value to HW. Reviewed-by: Björn Töpel Acked-by: Stanislav Fomichev Fixes: 24ea50127ecf ("xsk: support mbuf on ZC RX") Signed-off-by: Maciej Fijalkowski --- include/net/xdp_sock_drv.h | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h index 6b9ebae2dc95..dcf811c45b22 100644 --- a/include/net/xdp_sock_drv.h +++ b/include/net/xdp_sock_drv.h @@ -41,6 +41,19 @@ static inline u32 xsk_pool_get_headroom(struct xsk_buff_pool *pool) return XDP_PACKET_HEADROOM + pool->headroom; } +static inline u32 xsk_pool_get_tailroom(struct xsk_buff_pool *pool) +{ + struct xdp_umem *umem = pool->umem; + + /* Reserve tailroom only for zero-copy pools that opted into + * multi-buffer. The reserved area is used for skb_shared_info, + * matching the XDP core's xdp_data_hard_end() layout. + */ + if (pool->dev && (umem->flags & XDP_UMEM_SG_FLAG)) + return SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); + return 0; +} + static inline u32 xsk_pool_get_chunk_size(struct xsk_buff_pool *pool) { return pool->chunk_size; @@ -48,7 +61,9 @@ static inline u32 xsk_pool_get_chunk_size(struct xsk_buff_pool *pool) static inline u32 xsk_pool_get_rx_frame_size(struct xsk_buff_pool *pool) { - return xsk_pool_get_chunk_size(pool) - xsk_pool_get_headroom(pool); + return ALIGN_DOWN(xsk_pool_get_chunk_size(pool) - + xsk_pool_get_headroom(pool) - + xsk_pool_get_tailroom(pool), 128); } static inline u32 xsk_pool_get_rx_frag_step(struct xsk_buff_pool *pool) -- 2.43.0