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 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id D36CFC4332F for ; Mon, 30 Oct 2023 13:30:34 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qxRkX-0006dC-7T; Mon, 30 Oct 2023 08:52:09 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qxRkV-0006c9-UL for qemu-devel@nongnu.org; Mon, 30 Oct 2023 08:52:07 -0400 Received: from mail-lj1-x230.google.com ([2a00:1450:4864:20::230]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1qxRkT-0004w0-Ra for qemu-devel@nongnu.org; Mon, 30 Oct 2023 08:52:07 -0400 Received: by mail-lj1-x230.google.com with SMTP id 38308e7fff4ca-2c594196344so64428541fa.3 for ; Mon, 30 Oct 2023 05:52:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=daynix-com.20230601.gappssmtp.com; s=20230601; t=1698670324; x=1699275124; darn=nongnu.org; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=4ng2ChuYM/Z2YnskJMQA0+GcGB0Da/VKWSu82n4elek=; b=eNCIcRhZa3dPSrQ20kx9M+EBc/jkkTteDcc0+15FZNY71NyPGpoXBe7NxRonrYVPcO nlNr8teZaceFhYxGdBhJlxJXlMzThTMQQbaoCokI2ucVv2l3J/GArAdbWdFmFAJ6w83k x5V7yLiY7qMa9qYWvBTKZACYyBs0ByyXe0BFUPaFnXVZyRj9a4ztNsnp3qZYgUBzivSc LOLKx/BZ4ONADtMir4O0i+PSr3VKJYkeNXJI3YHsiWolYLy8zeEsBFlunUNS2xK4q6GF D0K5JOpNzXq73A89jZBtY3VbfcXGbr6kVu9ts8Z5OVD8i/rD189UU62exh3Xkyjiux/+ PrrQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1698670324; x=1699275124; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=4ng2ChuYM/Z2YnskJMQA0+GcGB0Da/VKWSu82n4elek=; b=ISAEYc9um9E1AZ3bcMlPz3JRLn4VZy4Y1MsB6Jk0PXszzoNVL+RLpWYv5P6+ywkoiO sfAMy95BjuHlHSv3c2hBKrghZ/JjTo9Yp9SEnB/kNpVLkuHZauss9WS3p7Aym30wkMjB QGrapwjdN8yv2YZmPn/zv2UAfAMCq94yXVi1C3vbgZPwewaokkc78E+0yv8gRB77QW7D FOqm2zc1bF5dQMupKVSfVQJ4Y3mcTX7ULgyYLaUg2dsdSXSEuWoLmUjloZVQ72eWC8It +d3odoAbLMuNxiQzzNqE+O3vaJq5joHSEr+zEP0ENodQeMUtIw1dMhMe1ZyZHdMFLsy2 GP9A== X-Gm-Message-State: AOJu0YxLL7cQyfzoo/fAQ37mSPjw3+kpmDGpYytZaZpRILxaN3DNzrrn s0A35yQxQAMv4L8z6UqNPyUsjbClwE4fYJi9gu/lXw== X-Google-Smtp-Source: AGHT+IGLeSfgnYcPx5EhVNej308zXVuBgGU4IIwyzPzz1UV29t2KpuZd4CJzl5MjpiZ4ezgXyPxRaMmrw0k4Rt0kBwc= X-Received: by 2002:a05:651c:119b:b0:2c5:14d1:a303 with SMTP id w27-20020a05651c119b00b002c514d1a303mr6570309ljo.25.1698670323811; Mon, 30 Oct 2023 05:52:03 -0700 (PDT) MIME-Version: 1.0 References: <20231030051356.33123-1-akihiko.odaki@daynix.com> <20231030051356.33123-12-akihiko.odaki@daynix.com> <58fb3b75-dd69-4715-a8ec-4c3df3b7e4c5@daynix.com> In-Reply-To: <58fb3b75-dd69-4715-a8ec-4c3df3b7e4c5@daynix.com> From: Yuri Benditovich Date: Mon, 30 Oct 2023 14:51:51 +0200 Message-ID: Subject: Re: [PATCH v6 11/21] virtio-net: Return an error when vhost cannot enable RSS To: Akihiko Odaki Cc: qemu-devel@nongnu.org, Andrew Melnychenko , "Michael S . Tsirkin" , Jason Wang Content-Type: multipart/alternative; boundary="0000000000003ddc1b0608ee810d" Received-SPF: none client-ip=2a00:1450:4864:20::230; envelope-from=yuri.benditovich@daynix.com; helo=mail-lj1-x230.google.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_NONE=0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org --0000000000003ddc1b0608ee810d Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, Oct 30, 2023 at 2:21=E2=80=AFPM Akihiko Odaki wrote: > On 2023/10/30 21:14, Yuri Benditovich wrote: > > > > > > On Mon, Oct 30, 2023 at 7:14=E2=80=AFAM Akihiko Odaki > > wrote: > > > > vhost requires eBPF for RSS. When eBPF is not available, virtio-net > > implicitly disables RSS even if the user explicitly requests it. > Return > > an error instead of implicitly disabling RSS if RSS is requested bu= t > not > > available. > > > > > > I think that suggesting RSS feature when in fact it is not available is > > not a good idea, this rather desinforms the guest. > > Existing behavior (IMHO) makes more sense. > > We can extend this discussion if needed, of course. > > This change is not to advertise RSS when it's not available; it instead > reports an error to the user. > > For example, think of the following command line: > qemu-system-x86_64 -device virtio-net,rss=3Don,netdev=3Dn -netdev user,id= =3Dn > > Before this change, it gives no error and the user will not know RSS is > not available. With this change it now gives an error as follows: > qemu-system-x86_64: -device virtio-net,rss=3Don,netdev=3Dn: Can't load eB= PF RSS > Does this mean failure to run QEMU if the RSS required in the command line and EBPF can't be loaded? (for example if we run the system with kernel < 5.8)? I'm not sure this is user-friendly behavior... --0000000000003ddc1b0608ee810d Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


=
On Mon, Oct 30, 2023 at 2:21=E2=80=AF= PM Akihiko Odaki <akihiko.od= aki@daynix.com> wrote:
On 2023/10/30 21:14, Yuri Benditovich wrote:
>
>
> On Mon, Oct 30, 2023 at 7:14=E2=80=AFAM Akihiko Odaki <akihiko.odaki@daynix.com<= /a>
> <mailto:akihiko.odaki@daynix.com>> wrote:
>
>=C2=A0 =C2=A0 =C2=A0vhost requires eBPF for RSS. When eBPF is not avail= able, virtio-net
>=C2=A0 =C2=A0 =C2=A0implicitly disables RSS even if the user explicitly= requests it. Return
>=C2=A0 =C2=A0 =C2=A0an error instead of implicitly disabling RSS if RSS= is requested but not
>=C2=A0 =C2=A0 =C2=A0available.
>
>
> I think that suggesting RSS feature when in fact it is not available i= s
> not a good idea, this rather desinforms the guest.
> Existing behavior (IMHO) makes more sense.
> We can extend this discussion if needed, of course.

This change is not to advertise RSS when it's not available; it instead=
reports an error to the user.

For example, think of the following command line:
qemu-system-x86_64 -device virtio-net,rss=3Don,netdev=3Dn -netdev user,id= =3Dn

Before this change, it gives no error and the user will not know RSS is not available. With this change it now gives an error as follows:
qemu-system-x86_64: -device virtio-net,rss=3Don,netdev=3Dn: Can't load = eBPF RSS

Does this mean failure to run = QEMU if the RSS required in the command line and EBPF can't be loaded?<= /div>
(for example if we run the system with kernel < 5.8)?
I'm not sure this is user-friendly behavior...
--0000000000003ddc1b0608ee810d--