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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 76F1DEB64D9 for ; Tue, 4 Jul 2023 10:39:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231545AbjGDKjh (ORCPT ); Tue, 4 Jul 2023 06:39:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52484 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231830AbjGDKjc (ORCPT ); Tue, 4 Jul 2023 06:39:32 -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 1493E186 for ; Tue, 4 Jul 2023 03:38:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1688467124; 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=QRorza6OJCiLsVesM2IH/LA8g4F1XVqMOWMx+3P1rz4=; b=WK6+siXTpMKYmAWxQnR86ytA49jxDOu82BBjafOwSP9jIlBDgFrpKEVv7FKPqiak5p9Fak fqDrmJPyBk3lm0WEf4frmkab6e6x8+UKDHtu4El8yM9f+vKku2f7eXqOmIPppSrZ15FuQu lG3xdFWvZvNkhPLOKaGazIarsmNA9l0= Received: from mail-lf1-f69.google.com (mail-lf1-f69.google.com [209.85.167.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-612-eYn1NZhvNNuWGlsuvcs_fw-1; Tue, 04 Jul 2023 06:38:41 -0400 X-MC-Unique: eYn1NZhvNNuWGlsuvcs_fw-1 Received: by mail-lf1-f69.google.com with SMTP id 2adb3069b0e04-4fb89482c48so4794938e87.3 for ; Tue, 04 Jul 2023 03:38:40 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1688467119; x=1691059119; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=QRorza6OJCiLsVesM2IH/LA8g4F1XVqMOWMx+3P1rz4=; b=lKF8+y36z9f+xby9qBK6tfNB05ZvpWDBraFVAwRoPi/5aKHB7QiORRq7JXoCAxa0UO +W0duA0aOZCBiPotkHFvG62vON8VBESlxO334YAqzHMkme7UbCeXkvGh64ApWFIZGAH5 0yykKLOnjnq8kiJHL3JOuibVhiXT5tPot1OZgHdCGPHU6fyo+xdjy1suf9l5egtRcMPk ZsWbxIHhzsybG4dk5kvZaC8nqoU05Bx5H4++F2d96sCy6XEX5Q7AnQf6QW4BImRosvkB /p7Mn70EL/nveaXZoYfbmTU0VKcvY4WzjehxNTDcqQVRQdzEFxlAHVHraf+MesPk27tK 6Myg== X-Gm-Message-State: ABy/qLb/oY5l/LyYBbE2hM+NHVisnV8tOidRJAc6WIiTw93+qetOCue1 lV/c1HKqQrCYHAYOWSJrti1b3zf5kmY55Px49xgXSxnJw6V2JwRlD+MQVf6/Pf3KnQEz/FqH28W KJ4Dk9iGW5XJI X-Received: by 2002:a05:6512:39d3:b0:4f7:405f:72e7 with SMTP id k19-20020a05651239d300b004f7405f72e7mr10638816lfu.50.1688467119713; Tue, 04 Jul 2023 03:38:39 -0700 (PDT) X-Google-Smtp-Source: APBJJlHGDGMjGihqxX02HuxnbdBtGBjZZQqY3m1CG+EemG0uaYcjxxZV8C9XGiMcmo2QCieoBmTukg== X-Received: by 2002:a05:6512:39d3:b0:4f7:405f:72e7 with SMTP id k19-20020a05651239d300b004f7405f72e7mr10638796lfu.50.1688467119354; Tue, 04 Jul 2023 03:38:39 -0700 (PDT) Received: from redhat.com ([2.52.13.33]) by smtp.gmail.com with ESMTPSA id z7-20020a05600c220700b003fa999cefc0sm23940722wml.36.2023.07.04.03.38.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Jul 2023 03:38:38 -0700 (PDT) Date: Tue, 4 Jul 2023 06:38:35 -0400 From: "Michael S. Tsirkin" To: Eugenio Perez Martin Cc: Jason Wang , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Shannon Nelson , virtualization@lists.linux-foundation.org, kvm@vger.kernel.org Subject: Re: [PATCH] vdpa: reject F_ENABLE_AFTER_DRIVER_OK if backend does not support it Message-ID: <20230704063646-mutt-send-email-mst@kernel.org> References: <20230703142218.362549-1-eperezma@redhat.com> <20230703105022-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Jul 04, 2023 at 12:25:32PM +0200, Eugenio Perez Martin wrote: > On Mon, Jul 3, 2023 at 4:52 PM Michael S. Tsirkin wrote: > > > > On Mon, Jul 03, 2023 at 04:22:18PM +0200, Eugenio Pérez wrote: > > > With the current code it is accepted as long as userland send it. > > > > > > Although userland should not set a feature flag that has not been > > > offered to it with VHOST_GET_BACKEND_FEATURES, the current code will not > > > complain for it. > > > > > > Since there is no specific reason for any parent to reject that backend > > > feature bit when it has been proposed, let's control it at vdpa frontend > > > level. Future patches may move this control to the parent driver. > > > > > > Fixes: 967800d2d52e ("vdpa: accept VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK backend feature") > > > Signed-off-by: Eugenio Pérez > > > > Please do send v3. And again, I don't want to send "after driver ok" hack > > upstream at all, I merged it in next just to give it some testing. > > We want RING_ACCESS_AFTER_KICK or some such. > > > > Current devices do not support that semantic. Which devices specifically access the ring after DRIVER_OK but before a kick? > My plan was to convert > it in vp_vdpa if needed, and reuse the current vdpa ops. Sorry if I > was not explicit enough. > > The only solution I can see to that is to trap & emulate in the vdpa > (parent?) driver, as talked in virtio-comment. But that complicates > the architecture: > * Offer VHOST_BACKEND_F_RING_ACCESS_AFTER_KICK > * Store vq enable state separately, at > vdpa->config->set_vq_ready(true), but not transmit that enable to hw > * Store the doorbell state separately, but do not configure it to the > device directly. > > But how to recover if the device cannot configure them at kick time, > for example? > > Maybe we can just fail if the parent driver does not support enabling > the vq after DRIVER_OK? That way no new feature flag is needed. > > Thanks! > > > > > > --- > > > Sent with Fixes: tag pointing to git.kernel.org/pub/scm/linux/kernel/git/mst > > > commit. Please let me know if I should send a v3 of [1] instead. > > > > > > [1] https://lore.kernel.org/lkml/20230609121244-mutt-send-email-mst@kernel.org/T/ > > > --- > > > drivers/vhost/vdpa.c | 7 +++++-- > > > 1 file changed, 5 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c > > > index e1abf29fed5b..a7e554352351 100644 > > > --- a/drivers/vhost/vdpa.c > > > +++ b/drivers/vhost/vdpa.c > > > @@ -681,18 +681,21 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep, > > > { > > > struct vhost_vdpa *v = filep->private_data; > > > struct vhost_dev *d = &v->vdev; > > > + const struct vdpa_config_ops *ops = v->vdpa->config; > > > void __user *argp = (void __user *)arg; > > > u64 __user *featurep = argp; > > > - u64 features; > > > + u64 features, parent_features = 0; > > > long r = 0; > > > > > > if (cmd == VHOST_SET_BACKEND_FEATURES) { > > > if (copy_from_user(&features, featurep, sizeof(features))) > > > return -EFAULT; > > > + if (ops->get_backend_features) > > > + parent_features = ops->get_backend_features(v->vdpa); > > > if (features & ~(VHOST_VDPA_BACKEND_FEATURES | > > > BIT_ULL(VHOST_BACKEND_F_SUSPEND) | > > > BIT_ULL(VHOST_BACKEND_F_RESUME) | > > > - BIT_ULL(VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK))) > > > + parent_features)) > > > return -EOPNOTSUPP; > > > if ((features & BIT_ULL(VHOST_BACKEND_F_SUSPEND)) && > > > !vhost_vdpa_can_suspend(v)) > > > -- > > > 2.39.3 > >