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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 A5F63C432C0 for ; Fri, 22 Nov 2019 16:58:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 78B3620672 for ; Fri, 22 Nov 2019 16:58:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="EZP63nav" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726686AbfKVQ57 (ORCPT ); Fri, 22 Nov 2019 11:57:59 -0500 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:51395 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726633AbfKVQ57 (ORCPT ); Fri, 22 Nov 2019 11:57:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1574441878; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=AvsGUy/REFNRPCWSB+iNYRuyQK+ahhfUg1D/UZDO1GU=; b=EZP63nav25bENJ0AlaHp8SrUtoT6jXm+hKfZwGuAuMd4v/nesFOsc8Vwt3C3E+HFhETRWb onnIL1B4OTRCK1h3ZC5g3ATwnpfsBE7LycSMhrHc35p8N1MF5lLmUECo1OTktYDPc1Xrh0 rnA7PICup7k9Y5V8EtSyeS7g6auIdsI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-377-MTnsNgBANeS-VTntiIgpBw-1; Fri, 22 Nov 2019 11:57:57 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0A5778DD804; Fri, 22 Nov 2019 16:57:56 +0000 (UTC) Received: from carbon (ovpn-200-17.brq.redhat.com [10.40.200.17]) by smtp.corp.redhat.com (Postfix) with ESMTP id 689EB6E71E; Fri, 22 Nov 2019 16:57:51 +0000 (UTC) Date: Fri, 22 Nov 2019 17:57:49 +0100 From: Jesper Dangaard Brouer To: David Ahern Cc: Jason Wang , "xdp-newbies@vger.kernel.org" , brouer@redhat.com, "netdev@vger.kernel.org" Subject: Re: error loading xdp program on virtio nic Message-ID: <20191122175749.47728e42@carbon> In-Reply-To: <8324a37e-5507-2ae6-53f6-949c842537e0@gmail.com> References: <89f56317-5955-e692-fcf0-ee876aae068b@redhat.com> <3dc7b9d8-bcb2-1a90-630e-681cbf0f1ace@gmail.com> <18659bd0-432e-f317-fa8a-b5670a91c5b9@redhat.com> <20191121072625.3573368f@carbon> <4686849f-f3b8-dd1d-0fe4-3c176a37b67a@redhat.com> <8324a37e-5507-2ae6-53f6-949c842537e0@gmail.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: MTnsNgBANeS-VTntiIgpBw-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, 22 Nov 2019 08:43:50 -0700 David Ahern wrote: > On 11/21/19 11:09 PM, Jason Wang wrote: > >> Doubling the number of queues for each tap device adds overhead to the > >> hypervisor if you only want to allow XDP_DROP or XDP_DIRECT. Am I > >> understanding that correctly? > > > > > > Yes, but there's almost impossible to know whether or not XDP_TX will be > > used by the program. If we don't use per CPU TX queue, it must be > > serialized through locks, not sure it's worth try that (not by default, > > of course). > > > > This restriction is going to prevent use of XDP in VMs in general cloud > hosting environments. 2x vhost threads for vcpus is a non-starter. > > If one XDP feature has high resource needs, then we need to subdivide > the capabilities to let some work and others fail. For example, a flag > can be added to xdp_buff / xdp_md that indicates supported XDP features. > If there are insufficient resources for XDP_TX, do not show support for > it. If a program returns XDP_TX anyways, packets will be dropped. > This sounds like concrete use-case and solid argument why we need XDP feature detection and checks. (Last part of LPC talk[1] were about XDP features). An interesting perspective you bring up, is that XDP features are not static per device driver. It actually needs to be dynamic, as your XDP_TX feature request depend on the queue resources available. Implementation wise, I would not add flags to xdp_buff / xdp_md. Instead I propose in[1] slide 46, that the verifier should detect the XDP features used by a BPF-prog. If you XDP prog doesn't use e.g. XDP_TX, then you should be allowed to run it on a virtio_net device with less queue configured, right? [1] http://people.netfilter.org/hawk/presentations/LinuxPlumbers2019/xdp-distro-view.pdf -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer