From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ed1-f46.google.com (mail-ed1-f46.google.com [209.85.208.46]) (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 52E7D21770C for ; Thu, 2 Oct 2025 11:46:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.46 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759405569; cv=none; b=qhrVpFsZO8zcmJaVasuhqFM9OEyjDbml+e6ueT13FRtVlO6/FltSouBzZQlmbKhRw3Pu6Y2Ysq9o9VDPwXChxgeL6bnnBa8DJjFnaVOCTeXkIcTE6tK0Jzsrdha7fpqaNsZfNt/IzSrVF9E5BMEW5xWjto7kOJh5w1mQQqA0Bu8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759405569; c=relaxed/simple; bh=cyIdpxNubhuvyduiL9ujFYBh9Qvgfd9olUvMSZ6MOH8=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=UvQcjN1PV18gu1JRGu1+soi2s6qSjA4RtrRIwzMRxI9auUw34RYg7szBKlETQ/3lOm7lbHPWZTW5SxvjnvksD1YC9HzDPVF0/1fRkfi+T5VBa3x2VGpIC9LhzE3Mm3bnXIW+mBIg2bXAZRdhKn3nvmXqFlbPZNswVbYRrmnX3rs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=cloudflare.com; spf=pass smtp.mailfrom=cloudflare.com; dkim=pass (2048-bit key) header.d=cloudflare.com header.i=@cloudflare.com header.b=GWgWwShS; arc=none smtp.client-ip=209.85.208.46 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=cloudflare.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=cloudflare.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=cloudflare.com header.i=@cloudflare.com header.b="GWgWwShS" Received: by mail-ed1-f46.google.com with SMTP id 4fb4d7f45d1cf-628f29d68ecso2169089a12.3 for ; Thu, 02 Oct 2025 04:46:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google09082023; t=1759405565; x=1760010365; darn=vger.kernel.org; h=mime-version:message-id:date:subject:cc:to:from:from:to:cc:subject :date:message-id:reply-to; bh=nnAbOpa9GWwA8Mzz91fJKN8c6IvbEOIGgFBBZyPX5NA=; b=GWgWwShSwP65Pw8gqOM5pzOnnI7zSm7KGg9RtF5gk7R+suKm1VUruMZdEtgO1bTX+O /IhQ9IYjeQMrEToOT95pS7qxspr1i0Ibgob6O1Ju79CET8jIYYql3t1itmM8/MwxGLQb vjx6JhbnlvObf+S/4Wbs9DWMbzdAmo753lIpwQXVvTqk4hzEyI6p1kzvgsXewu1bvWNq 9BNjy+nOTQqiKFRHNjdRrrbD1kj4e1EsjwmtXKgA525lByyl7FPo+cihGk4KyC/UUnBO PQ8kFQMvq7gZTlHZ5gbmdeZ03kqz2FDsSLITBgcje++2gw0KKbxDWD9xLZMipeudfiB7 7VTQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1759405565; x=1760010365; h=mime-version:message-id:date:subject:cc:to:from:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=nnAbOpa9GWwA8Mzz91fJKN8c6IvbEOIGgFBBZyPX5NA=; b=W2ab3nXzaS/bau7a59jaDEuh82NHxPHkdCpxxkvkVx55ufhD8Dnnk4QRF4py/n5IPW WioTwyqmfhhEzakLEi8TobtCVK8LNDr23xn6kS5Pnb390EooOmLsSiUz8eOCqtBe3c/9 d4UUrmss9+kWxUlLir0kuTSw18bl9x1xx48SB52l69wG2XulzDlGAkKHxflxiLIzNtug wi8jYBEnukxaaxF7CyFr3/AkSDWATNFT4H/F0glDMYAjDrQr/WsJ3aOipH3+BpDv+LMK 5f3RvBWt5B15lD1Gg0kmvgtHQt0fKmD2JokxfNoLU2gm4325NizoqErsirb1OBmPp/4Z PRYA== X-Gm-Message-State: AOJu0YxEVxfmO96Q7yoRckatUxhhohlembeKdjytFuKYThKt1uqwXtd/ w0de6+GkHnnltXwtulMxNYGkJTdcloIgx1jXzxYuIOdduBxTChpeiqjH+UgM63L/Xk0= X-Gm-Gg: ASbGnctZQkjTaiqTwXCLrna72pz9JuEx8AwGAZHwVnQmz2ACkK6bjpDLz6G62OPodkm UHpk3SU0d2puCrQ1jTZfONjHUvZ+oaxPX79e50RLzJHvL75iEqJWuVtAN0yJBcyKE+5qiX8eWya plXQyiWhyOu82SSZcPTshNQR09wjk3vPtIeOyTyYVrAVS/7thScRYf2ILJ/BOXQdnFsegOp55iR 4RZW4D28iXhaAr9Tdy7TLIC0XgofwfW1Zmq5u/6jbndvgv/Nt7DlIL0sI+XH+5odN+dsbFGakq9 CP6jqAbKi5PmOGdv569RB4WhT/Dk96hAKMjoFTZ7eR4uZUyXfgK3s/vyWJpIhF12tohX+IP4n4Q NMXXXr0YDKcFiG3H0SUfPywvcahBvsJSeT2ZG5w== X-Google-Smtp-Source: AGHT+IGkuWTBkQWQsXWA2WSywVPtCOF6XTskC6I1+kyLAhpousf+DMtrvWH/4v50S+KzgF58+1ViHg== X-Received: by 2002:a17:907:948f:b0:b30:2f6b:448f with SMTP id a640c23a62f3a-b46e6816e14mr873905666b.25.1759405564608; Thu, 02 Oct 2025 04:46:04 -0700 (PDT) Received: from cloudflare.com ([2a09:bac6:d677:2dc::49:1c8]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b4869b57f0asm187094166b.77.2025.10.02.04.46.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Oct 2025 04:46:03 -0700 (PDT) From: Jakub Sitnicki To: Sunil Goutham , Geetha sowjanya , Subbaraya Sundeep , hariprasad , Bharat Bhushan Cc: netdev@vger.kernel.org Subject: marvell/octeontx2: XDP vs skb headroom reservation Date: Thu, 02 Oct 2025 13:46:02 +0200 Message-ID: <87h5wh34sl.fsf@cloudflare.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Hi, I'm auditing calls to skb_metadata_set() in drivers and something seems off in oceontx2. I may be completely misreading the code. I'm a total stranger to that driver. It would seem that there is a difference between the amount of headroom that the driver reserves for the XDP buffer vs the skb that is built from on that buffer, while the two should match. In the receive handler we have: otx2_rcv_pkt_handler otx2_xdp_rcv_pkt_handler if pfvf->xdp_prog xdp_prepare_buff(..., OTX2_HEAD_ROOM, ...) where OTX2_HEAD_ROOM = OTX2_ALIGN = 128 skb = napi_get_frags napi_alloc_skb skb_reserve(NET_SKB_PAD + NET_IP_ALIGN) where NET_SKB_PAD = 64, NET_IP_ALIGN = 0 on x86 napi_gro_frags There are no other calls to skb_reserve there, so we seem to have a mismatch. 128B of headroom in XDP buff, and only 64B of headroom in skb head. Again, I could be totally wrong about this, I'm not familiar with the driver, but I thought you might want to double check this. Thanks, -jkbs