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[2620:137:e000::1:20]) by mx.google.com with ESMTP id bv9-20020a632e09000000b0055b990f440bsi6610740pgb.242.2023.07.04.23.05.03; Tue, 04 Jul 2023 23:05:21 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=DF4XqnWo; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231250AbjGEFs6 (ORCPT + 99 others); Wed, 5 Jul 2023 01:48:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57846 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230401AbjGEFs4 (ORCPT ); Wed, 5 Jul 2023 01:48:56 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6FE53B2 for ; Tue, 4 Jul 2023 22:48:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1688536081; 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=WmroFXVskoyZWXutVUB2JGgpokOFhXT+2nZZqoGKkeE=; b=DF4XqnWoT0ZrZ0AQzmmEBSrAA2/FKs6Y82ZiPbNoDldKdCe3sbxhm4OcyDsCTZZZApRulJ B6c2fesrm2CS5UASq0chhbEBDia0islRanfq4Vwpth7ju2lquXC++F7pKkY1oLk/KBgWOY Lo+VkpRCzKbYXbdkG88hA4qP8WS+Jnw= Received: from mail-lj1-f197.google.com (mail-lj1-f197.google.com [209.85.208.197]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-561-aROfJT6wOlqiitrR74gHDg-1; Wed, 05 Jul 2023 01:47:59 -0400 X-MC-Unique: aROfJT6wOlqiitrR74gHDg-1 Received: by mail-lj1-f197.google.com with SMTP id 38308e7fff4ca-2b6ff1520c4so2839031fa.1 for ; Tue, 04 Jul 2023 22:47:59 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1688536077; x=1691128077; h=content-transfer-encoding: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=WmroFXVskoyZWXutVUB2JGgpokOFhXT+2nZZqoGKkeE=; b=jIY+uA1ezrH28B0o+36ZYz19cWI1o/2c/CtYKU4rBJhWE/HwqZCuo3Y6V92CyhUYfo d9bseTw3rxBqFkkHcySDkfgX4gUOo2K4V4NfCDiswOH1XuW2IKX14sDX7U7ecd1kD4n4 0vwJ+X+oYMBAPOaQRTWr4Roo88izx09A90XqCol+ykPDOlsYF1Q9m9yNtw8qKjB3Ynfa TgZMDwf1haLGwenFdp6iwpOcTVatlN4dgss379VdT0Wl9D+GKtTIhIRAofSbUl8ElrjZ 0oHsAv3K3hDtwfB+pBcw3VoeDGCdL91hi8DMXO9RKEN57ucL9yWZJAm5+n4vJ5cwMUIK Ratw== X-Gm-Message-State: ABy/qLacrfWeCxZXW0nGpexS7ToAjY66AlcweTVAZjsTYtlR24a6+cT6 lSZUxD0Nr+s554aoMLleKhsSoGGSdSEREyLS5KdsTMjj2cqmoLwtM6997ynylAFfQxAPgNXM1RG 6a3DphpZS0aEK1j5jTms5lpbFM58nQnz1MP6qBnYvm1RW6ac6JZg= X-Received: by 2002:a2e:3009:0:b0:2b6:cca1:9760 with SMTP id w9-20020a2e3009000000b002b6cca19760mr11268077ljw.27.1688536077505; Tue, 04 Jul 2023 22:47:57 -0700 (PDT) X-Received: by 2002:a2e:3009:0:b0:2b6:cca1:9760 with SMTP id w9-20020a2e3009000000b002b6cca19760mr11268038ljw.27.1688536076088; Tue, 04 Jul 2023 22:47:56 -0700 (PDT) MIME-Version: 1.0 References: <20230703142514.363256-1-eperezma@redhat.com> <20230703110241-mutt-send-email-mst@kernel.org> <20230704061356-mutt-send-email-mst@kernel.org> <20230705012917-mutt-send-email-mst@kernel.org> In-Reply-To: <20230705012917-mutt-send-email-mst@kernel.org> From: Jason Wang Date: Wed, 5 Jul 2023 13:47:44 +0800 Message-ID: Subject: Re: [PATCH] mlx5_vdpa: offer VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK To: "Michael S. Tsirkin" Cc: Si-Wei Liu , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , linux-kernel@vger.kernel.org, Dragos Tatulea , virtualization@lists.linux-foundation.org, leiyang@redhat.com, Xuan Zhuo Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 5, 2023 at 1:31=E2=80=AFPM Michael S. Tsirkin = wrote: > > On Wed, Jul 05, 2023 at 01:11:37PM +0800, Jason Wang wrote: > > On Tue, Jul 4, 2023 at 6:16=E2=80=AFPM Michael S. Tsirkin wrote: > > > > > > On Mon, Jul 03, 2023 at 05:26:02PM -0700, Si-Wei Liu wrote: > > > > > > > > > > > > On 7/3/2023 8:46 AM, Michael S. Tsirkin wrote: > > > > > On Mon, Jul 03, 2023 at 04:25:14PM +0200, Eugenio P=C3=A9rez wrot= e: > > > > > > Offer this backend feature as mlx5 is compatible with it. It al= lows it > > > > > > to do live migration with CVQ, dynamically switching between pa= ssthrough > > > > > > and shadow virtqueue. > > > > > > > > > > > > Signed-off-by: Eugenio P=C3=A9rez > > > > > Same comment. > > > > to which? > > > > > > > > -Siwei > > > > > > VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK is too narrow a use-case to co= mmit to it > > > as a kernel/userspace ABI: what if one wants to start rings in some > > > other specific order? > > > > Just enable a queue by writing e.g 1 to queue_enable in a specific orde= r? > > > But then at driver ok time we don't know how many queues are there. There should be a device specific interface for this, for example, num_queue_paris. So the device knows at most how many queues there are. Or anything I miss? > > > > As was discussed on list, a better promise is not to access ring > > > until the 1st kick. vdpa can then do a kick when it wants > > > the device to start accessing rings. > > > > Rethink about the ACCESS_AFTER_KICK, it sounds functional equivalent > > to allow queue_enable after DRIVER_OK, but it seems to have > > distanvages: > > > > A busy polling software device may disable notifications and never > > respond to register to any kick notifiers. ACCESS_AFTER_KICK will > > introduce overhead to those implementations. > > > > Thanks > > It's just the 1st kick, then you can disable. No? Yes, but: 1) adding hooks for queue_enable 2) adding new codes to register event notifier and toggle the notifier 1) seems much easier? Or for most devices, it already behaves like this. Thanks > > > > > > > > > > > > > > > --- > > > > > > drivers/vdpa/mlx5/net/mlx5_vnet.c | 7 +++++++ > > > > > > 1 file changed, 7 insertions(+) > > > > > > > > > > > > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/m= lx5/net/mlx5_vnet.c > > > > > > index 9138ef2fb2c8..5f309a16b9dc 100644 > > > > > > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c > > > > > > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c > > > > > > @@ -7,6 +7,7 @@ > > > > > > #include > > > > > > #include > > > > > > #include > > > > > > +#include > > > > > > #include > > > > > > #include > > > > > > #include > > > > > > @@ -2499,6 +2500,11 @@ static void unregister_link_notifier(str= uct mlx5_vdpa_net *ndev) > > > > > > flush_workqueue(ndev->mvdev.wq); > > > > > > } > > > > > > +static u64 mlx5_vdpa_get_backend_features(const struct vdpa_de= vice *vdpa) > > > > > > +{ > > > > > > + return BIT_ULL(VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK); > > > > > > +} > > > > > > + > > > > > > static int mlx5_vdpa_set_driver_features(struct vdpa_device *= vdev, u64 features) > > > > > > { > > > > > > struct mlx5_vdpa_dev *mvdev =3D to_mvdev(vdev); > > > > > > @@ -3140,6 +3146,7 @@ static const struct vdpa_config_ops mlx5_= vdpa_ops =3D { > > > > > > .get_vq_align =3D mlx5_vdpa_get_vq_align, > > > > > > .get_vq_group =3D mlx5_vdpa_get_vq_group, > > > > > > .get_device_features =3D mlx5_vdpa_get_device_feature= s, > > > > > > + .get_backend_features =3D mlx5_vdpa_get_backend_features, > > > > > > .set_driver_features =3D mlx5_vdpa_set_driver_feature= s, > > > > > > .get_driver_features =3D mlx5_vdpa_get_driver_feature= s, > > > > > > .set_config_cb =3D mlx5_vdpa_set_config_cb, > > > > > > -- > > > > > > 2.39.3 > > > >