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[2620:137:e000::1:20]) by mx.google.com with ESMTP id w6-20020a634906000000b0055b6a784893si893726pga.520.2023.07.06.00.12.32; Thu, 06 Jul 2023 00:12:44 -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="heS30NX/"; 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 S233663AbjGFGhD (ORCPT + 99 others); Thu, 6 Jul 2023 02:37:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53620 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233477AbjGFGhC (ORCPT ); Thu, 6 Jul 2023 02:37:02 -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 CF8C21737 for ; Wed, 5 Jul 2023 23:36:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1688625369; 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=RW6sZxQEq7r6/MAdcOAFMIZmsNq8xRUmGtzjXz5LxLU=; b=heS30NX/F4UuR0Kyl14wIf0YOGIqchhkDqcy2nuFC76XTqri3EH7Dov1pcgUMep1bZKsRN B9pYfk0xerNuOiVJFJE4wuvJjLDNRVe/j/6uNf6Bm6RoCw+ydsweeaddgR9hlSM3wmhe1p 52XpH9syonfavtiAnRP4KgqoGnrYilI= Received: from mail-yb1-f197.google.com (mail-yb1-f197.google.com [209.85.219.197]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-361--RLlLIvVMN6UQQV8odiUGQ-1; Thu, 06 Jul 2023 02:36:07 -0400 X-MC-Unique: -RLlLIvVMN6UQQV8odiUGQ-1 Received: by mail-yb1-f197.google.com with SMTP id 3f1490d57ef6-c4e0342c50dso331338276.2 for ; Wed, 05 Jul 2023 23:36:07 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1688625367; x=1691217367; 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=RW6sZxQEq7r6/MAdcOAFMIZmsNq8xRUmGtzjXz5LxLU=; b=cH0iyun1dGzU2Ao8DW+fTcWQFXY9+KGbtqD8X61Dj4lNNz7ij9IyZJCCSYzVVoJ3Of TjR0Y7GHOcsIaGnxc/qT+uhdchHhTgoqEqXddvaffT5B27iPrRZb5IOyI9QF24NkgUkN 4ZaRnPsIwBlFDHCXpY8GWwM6zWOzcwNPYqsKFpZydZRfWW7pXQGkTIXSe7gCUJ2yiEYU LsIkVo0V0YLu2divN01PPeQqILC5ebYKngQ7QVdWYGKhgwxAzlcypmJcvJ2NjLoIEN2R 8e2iBa1MfcDKR3reAK1SUIAMm8hMldLBlyxmBe7dXyJY/nw4sagiW6tQasoRa5VRuB6w uI5A== X-Gm-Message-State: ABy/qLY58mofNOE+bpkWV3sCCf9614XVgcMQgALOFK5fwsfBY/aDzqvW n+Ln6Yl64PRIZsAL1rH4GeX6gjq3kQbWV0nKBr3Y4CNQBlNKR05LzhoeVeLijCUPoWhhvFQUXo4 FFmszfVeQF/EYysh1Pz0P9gLkmANgK+r5LwNn0B28puzEdR5/ X-Received: by 2002:a25:abe4:0:b0:c5c:616:39cb with SMTP id v91-20020a25abe4000000b00c5c061639cbmr975945ybi.14.1688625367166; Wed, 05 Jul 2023 23:36:07 -0700 (PDT) X-Received: by 2002:a25:abe4:0:b0:c5c:616:39cb with SMTP id v91-20020a25abe4000000b00c5c061639cbmr975933ybi.14.1688625366902; Wed, 05 Jul 2023 23:36:06 -0700 (PDT) MIME-Version: 1.0 References: <20230703142218.362549-1-eperezma@redhat.com> <20230703105022-mutt-send-email-mst@kernel.org> <20230704063646-mutt-send-email-mst@kernel.org> <20230704114159-mutt-send-email-mst@kernel.org> <20230706020603-mutt-send-email-mst@kernel.org> In-Reply-To: <20230706020603-mutt-send-email-mst@kernel.org> From: Eugenio Perez Martin Date: Thu, 6 Jul 2023 08:35:30 +0200 Message-ID: Subject: Re: [PATCH] vdpa: reject F_ENABLE_AFTER_DRIVER_OK if backend does not support it To: "Michael S. Tsirkin" Cc: Shannon Nelson , Jason Wang , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org 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 Thu, Jul 6, 2023 at 8:07=E2=80=AFAM Michael S. Tsirkin = wrote: > > On Wed, Jul 05, 2023 at 05:07:11PM -0700, Shannon Nelson wrote: > > On 7/5/23 11:27 AM, Eugenio Perez Martin wrote: > > > > > > On Wed, Jul 5, 2023 at 9:50=E2=80=AFAM Jason Wang wrote: > > > > > > > > On Tue, Jul 4, 2023 at 11:45=E2=80=AFPM Michael S. Tsirkin wrote: > > > > > > > > > > On Tue, Jul 04, 2023 at 01:36:11PM +0200, Eugenio Perez Martin wr= ote: > > > > > > On Tue, Jul 4, 2023 at 12:38=E2=80=AFPM Michael S. Tsirkin wrote: > > > > > > > > > > > > > > On Tue, Jul 04, 2023 at 12:25:32PM +0200, Eugenio Perez Marti= n wrote: > > > > > > > > On Mon, Jul 3, 2023 at 4:52=E2=80=AFPM Michael S. Tsirkin <= mst@redhat.com> wrote: > > > > > > > > > > > > > > > > > > On Mon, Jul 03, 2023 at 04:22:18PM +0200, Eugenio P=C3=A9= rez wrote: > > > > > > > > > > With the current code it is accepted as long as userlan= d send it. > > > > > > > > > > > > > > > > > > > > Although userland should not set a feature flag that ha= s not been > > > > > > > > > > offered to it with VHOST_GET_BACKEND_FEATURES, the curr= ent code will not > > > > > > > > > > complain for it. > > > > > > > > > > > > > > > > > > > > Since there is no specific reason for any parent to rej= ect 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 pare= nt driver. > > > > > > > > > > > > > > > > > > > > Fixes: 967800d2d52e ("vdpa: accept VHOST_BACKEND_F_ENAB= LE_AFTER_DRIVER_OK backend feature") > > > > > > > > > > Signed-off-by: Eugenio P=C3=A9rez > > > > > > > > > > > > > > > > > > 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 bu= t before > > > > > > > a kick? > > > > The PDS vdpa device can deal with a call to .set_vq_ready after DRIVER_= OK is > > set. And I'm told that our VQ activity should start without a kick. > > > > Our vdpa device FW doesn't currently have support for VIRTIO_F_RING_RES= ET, > > but I believe it could be added without too much trouble. > > > > sln > > > > OK it seems clear at least in the current version pds needs > VHOST_BACKEND_F_ENABLE_AFTER_DRIVER_OK. > However can we also code up the RING_RESET path as the default? > Then down the road vendors can choose what to do. > Yes, the RING_RESET path can be coded & tested for vp_vdpa, for example. I'm ok with making it the default, and let _F_ENABLE_AFTER_DRIVER_OK as a fallback. > > > > > > > > > > > > > > > > > > > > > > > Previous versions of the QEMU LM series did a spurious kick to = start > > > > > > traffic at the LM destination [1]. When it was proposed, that s= purious > > > > > > kick was removed from the series because to check for descripto= rs > > > > > > after driver_ok, even without a kick, was considered work of th= e > > > > > > parent driver. > > > > > > > > > > > > I'm ok to go back to this spurious kick, but I'm not sure if th= e hw > > > > > > will read the ring before the kick actually. I can ask. > > > > > > > > > > > > Thanks! > > > > > > > > > > > > [1] https://lists.nongnu.org/archive/html/qemu-devel/2023-01/ms= g02775.html > > > > > > > > > > Let's find out. We need to check for ENABLE_AFTER_DRIVER_OK too, = no? > > > > > > > > My understanding is [1] assuming ACCESS_AFTER_KICK. This seems > > > > sub-optimal than assuming ENABLE_AFTER_DRIVER_OK. > > > > > > > > But this reminds me one thing, as the thread is going too long, I > > > > wonder if we simply assume ENABLE_AFTER_DRIVER_OK if RING_RESET is > > > > supported? > > > > > > > > > > The problem with that is that the device needs to support all > > > RING_RESET, like to be able to change vq address etc after DRIVER_OK. > > > Not all HW support it. > > > > > > We just need the subset of having the dataplane freezed until all CVQ > > > commands have been consumed. I'm sure current vDPA code already > > > supports it in some devices, like MLX and PSD. > > > > > > Thanks! > > > > > > > Thanks > > > > > > > > > > > > > > > > > > > > > > > > > > > My plan was to convert > > > > > > > > it in vp_vdpa if needed, and reuse the current vdpa ops. So= rry 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 com= plicates > > > > > > > > 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 ena= ble 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 k= ick time, > > > > > > > > for example? > > > > > > > > > > > > > > > > Maybe we can just fail if the parent driver does not suppor= t enabling > > > > > > > > the vq after DRIVER_OK? That way no new feature flag is nee= ded. > > > > > > > > > > > > > > > > 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-se= nd-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_i= octl(struct file *filep, > > > > > > > > > > { > > > > > > > > > > struct vhost_vdpa *v =3D filep->private_data; > > > > > > > > > > struct vhost_dev *d =3D &v->vdev; > > > > > > > > > > + const struct vdpa_config_ops *ops =3D v->vdpa->co= nfig; > > > > > > > > > > void __user *argp =3D (void __user *)arg; > > > > > > > > > > u64 __user *featurep =3D argp; > > > > > > > > > > - u64 features; > > > > > > > > > > + u64 features, parent_features =3D 0; > > > > > > > > > > long r =3D 0; > > > > > > > > > > > > > > > > > > > > if (cmd =3D=3D VHOST_SET_BACKEND_FEATURES) { > > > > > > > > > > if (copy_from_user(&features, featurep, = sizeof(features))) > > > > > > > > > > return -EFAULT; > > > > > > > > > > + if (ops->get_backend_features) > > > > > > > > > > + parent_features =3D ops->get_back= end_features(v->vdpa); > > > > > > > > > > if (features & ~(VHOST_VDPA_BACKEND_FEAT= URES | > > > > > > > > > > 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 > > > > > > > > > > > > > > > > > > > > > > > > > > > > >