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[2620:137:e000::1:20]) by mx.google.com with ESMTP id f18-20020a635552000000b005577100c774si22061833pgm.869.2023.07.04.22.24.45; Tue, 04 Jul 2023 22:24:58 -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=jCqPV3KQ; 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 S230513AbjGEFMm (ORCPT + 99 others); Wed, 5 Jul 2023 01:12:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47448 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229449AbjGEFMl (ORCPT ); Wed, 5 Jul 2023 01:12:41 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EFFBE10E3 for ; Tue, 4 Jul 2023 22:11:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1688533912; 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=tO3P2mQX6+9ZgDhiDUsWuq97gou5mJ4BQnOKdZt/xjA=; b=jCqPV3KQS84kngkXQg1F4r2aIHd8MT0BR2C8OSdntRzwC04xtdm3pm3vWZiRUErAkpd1N6 1+s7NxRBBQaYj3EyCygXaauSW0i6AkhrHz5JfppVAlfU/3ra5o2ASe2eXIrnc8NX4JbN02 AG+B2KzFA4Mwv0z6BGuSgfYfL1AAtPw= Received: from mail-lj1-f199.google.com (mail-lj1-f199.google.com [209.85.208.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-244-HDgFt1CYOqO_D9UIyuisgA-1; Wed, 05 Jul 2023 01:11:51 -0400 X-MC-Unique: HDgFt1CYOqO_D9UIyuisgA-1 Received: by mail-lj1-f199.google.com with SMTP id 38308e7fff4ca-2b6a2a5f08aso61467301fa.2 for ; Tue, 04 Jul 2023 22:11:50 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1688533909; x=1691125909; 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=tO3P2mQX6+9ZgDhiDUsWuq97gou5mJ4BQnOKdZt/xjA=; b=DPXT8oWgyUJNxNUbThqFLofxdvLdAwLRhEZaEpyevzb78tRyQqOIMOuNUkXqEvIbUc qynNxgfIOaj4Q4coRqj2ZkLvhtTS4PdDi87u56jXrkrtRqRwezvGFcJI75qirAnPI826 /O620Niu0wCAUmgfDeO3v8VpMbcM76qmx5nfSLEiPu2UtIog5bdYxii4uZefpE+B4l1b RBvlhpx4TwrVjLVvtOb0iBcEg4rkcSwXnR820XC8eYlyAzw0yzb5Wx+0U7d8scBrwuVW hEv16G6AmvRxxAdMgXsh5sTvR6nDKOVMtMBsllsJKdat6+3sRqAdniFgRXPc24psysHW kqyQ== X-Gm-Message-State: ABy/qLYMEBwP4VqAPTxTpFDNO0beTuMTmChVa4lwSPXjL7r+wxri0WFA nWF0tTRVgZ6Q8jbhUnMvTnqCOj6c8JfeBoTadDeVVpZ316YP4YWNAAllGYGrV1s0NveuxQ4CYGp UQ+gC3xlf0lV01kP60b0NKt3GQh0BN+trWlXD5/V8 X-Received: by 2002:a2e:9104:0:b0:2b6:9c1d:dea3 with SMTP id m4-20020a2e9104000000b002b69c1ddea3mr11475461ljg.2.1688533909764; Tue, 04 Jul 2023 22:11:49 -0700 (PDT) X-Received: by 2002:a2e:9104:0:b0:2b6:9c1d:dea3 with SMTP id m4-20020a2e9104000000b002b69c1ddea3mr11475446ljg.2.1688533909459; Tue, 04 Jul 2023 22:11:49 -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> In-Reply-To: <20230704061356-mutt-send-email-mst@kernel.org> From: Jason Wang Date: Wed, 5 Jul 2023 13:11:37 +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 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 wrote: > > > > Offer this backend feature as mlx5 is compatible with it. It allows= it > > > > to do live migration with CVQ, dynamically switching between passth= rough > > > > 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 commit= 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 order? > 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 > > > > > > > > --- > > > > 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/mlx5/= 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(struct = mlx5_vdpa_net *ndev) > > > > flush_workqueue(ndev->mvdev.wq); > > > > } > > > > +static u64 mlx5_vdpa_get_backend_features(const struct vdpa_device= *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_features, > > > > + .get_backend_features =3D mlx5_vdpa_get_backend_features, > > > > .set_driver_features =3D mlx5_vdpa_set_driver_features, > > > > .get_driver_features =3D mlx5_vdpa_get_driver_features, > > > > .set_config_cb =3D mlx5_vdpa_set_config_cb, > > > > -- > > > > 2.39.3 >