From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4123CC2D0DB for ; Thu, 23 Jan 2020 17:30:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 17A4A21734 for ; Thu, 23 Jan 2020 17:30:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579800617; bh=rmA6KyDbqwAsoSEXaVkYOuGxZZeh0dbF4LK/1h1tWSo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=HdE7t7rtz3dQQyhcG5TjgbtZ3Xjt4YXait9mGbhotVOCL0FdBS0Ef6Zf6QgGyWTV3 j+kY0eSvqNRDB7O1SMKWDPaVhcl4Ow4E6WlmQUOulqT/pL6Gru5EXOit/SlV3NqOq+ IwH1xNcG9nda8RVnwmUsMFHBUTqjo+SUeLzhIVcU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729108AbgAWRaQ (ORCPT ); Thu, 23 Jan 2020 12:30:16 -0500 Received: from mail.kernel.org ([198.145.29.99]:48664 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728911AbgAWRaP (ORCPT ); Thu, 23 Jan 2020 12:30:15 -0500 Received: from cakuba (unknown [199.201.64.139]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 544DF21569; Thu, 23 Jan 2020 17:30:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579800614; bh=rmA6KyDbqwAsoSEXaVkYOuGxZZeh0dbF4LK/1h1tWSo=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ezgS0Cf2xaRVBA5xIs0nTkBbjVPaqD3v9CXNTpxEPfBjUIcEBgqpToKeCABolLuER yRSd/GyTRk63WVb4XL3FRV/PbUEEHULCoFoxk0RwwxnglXgPwgJ+i7gxE2AAO2pamh lKZF5FpL/RiHuFx71XNMQ/DePMO79XFCZw+OZ4LM= Date: Thu, 23 Jan 2020 09:30:13 -0800 From: Jakub Kicinski To: Haiyang Zhang Cc: "sashal@kernel.org" , "linux-hyperv@vger.kernel.org" , "netdev@vger.kernel.org" , KY Srinivasan , Stephen Hemminger , "olaf@aepfle.de" , vkuznets , "davem@davemloft.net" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH V3,net-next, 1/2] hv_netvsc: Add XDP support Message-ID: <20200123093013.53d78485@cakuba> In-Reply-To: References: <1579713814-36061-1-git-send-email-haiyangz@microsoft.com> <1579713814-36061-2-git-send-email-haiyangz@microsoft.com> <20200123085906.20608707@cakuba> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 23 Jan 2020 17:14:06 +0000, Haiyang Zhang wrote: > > > Changes: > > > v3: Minor code and comment updates. > > > v2: Added XDP_TX support. Addressed review comments. > > > > How does the locking of the TX path work? You seem to be just calling the > > normal xmit method, but you don't hold the xmit queue lock, so the stack can > > start xmit concurrently, no? > > The netvsc and vmbus can handle concurrent transmits, except the msd > (Multi-Send Data) field which can only be used by one queue. > > I already added a new flag to netvsc_send(), so packets from XDP_TX won't use > the msd. I see, there's a few non-atomic counters there, but maybe that's not a big deal. What frees the skb if the ring is full, and netvsc_send_pkt() returns -EAGAIN? Nothing checks the return value from netvsc_xdp_xmit().