From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 5 Oct 2023 13:08:52 -0400 From: Stefan Hajnoczi Message-ID: <20231005170852.GB1342722@fedora> References: <20231004125904.110781-1-hreitz@redhat.com> <20231004125904.110781-2-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="g2QTlaeqbOs+6JNr" Content-Disposition: inline In-Reply-To: <20231004125904.110781-2-hreitz@redhat.com> Subject: Re: [Virtio-fs] [PATCH v4 1/8] vhost-user.rst: Deprecate [GS]ET_STATUS List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Hanna Czenczek Cc: qemu-devel@nongnu.org, virtio-fs@redhat.com, "Michael S . Tsirkin" , German Maglione , Eugenio =?iso-8859-1?Q?P=E9rez?= , Anton Kuchin --g2QTlaeqbOs+6JNr Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Oct 04, 2023 at 02:58:57PM +0200, Hanna Czenczek wrote: > There is no clearly defined purpose for the virtio status byte in > vhost-user: For resetting, we already have RESET_DEVICE; and for virtio > feature negotiation, we have [GS]ET_FEATURES. With the REPLY_ACK > protocol extension, it is possible for SET_FEATURES to return errors > (SET_PROTOCOL_FEATURES may be called before SET_FEATURES). >=20 > As for implementations, SET_STATUS is not widely implemented. dpdk does > implement it, but only uses it to signal feature negotiation failure. > While it does log reset requests (SET_STATUS 0) as such, it effectively > ignores them, in contrast to RESET_OWNER (which is deprecated, and today > means the same thing as RESET_DEVICE). >=20 > While qemu superficially has support for [GS]ET_STATUS, it does not > forward the guest-set status byte, but instead just makes it up > internally, and actually completely ignores what the back-end returns, > only using it as the template for a subsequent SET_STATUS to add single > bits to it. Notably, after setting FEATURES_OK, it never reads it back > to see whether the flag is still set, which is the only way in which > dpdk uses the status byte. >=20 > As-is, no front-end or back-end can rely on the other side handling this > field in a useful manner, and it also provides no practical use over > other mechanisms the vhost-user protocol has, which are more clearly > defined. Deprecate it. >=20 > Suggested-by: Stefan Hajnoczi > Signed-off-by: Hanna Czenczek > --- > docs/interop/vhost-user.rst | 28 +++++++++++++++++++++------- > 1 file changed, 21 insertions(+), 7 deletions(-) Reviewed-by: Stefan Hajnoczi --g2QTlaeqbOs+6JNr Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmUe7aQACgkQnKSrs4Gr c8j32wgAtMdUBKzt8i0RX1vm+5YZjCyIkwymLuqS1sgqzwaa7sFTdEzVUD05tPWQ SCLw+j/yfDHVX0MrCYkMQLuUK6pW9g+tVKVoX34t1p/qYs3L3pikkMzBZARG7iQV 9jLmQJRf5VmXYwkWxfO6KR+sanlLFKgrRQ3rvFJChDMO2nNpuaS5cKtNZYRmlDVe NrOSBleWq1Fkph6tLtV62dNsxcxf48Hm1LUCecOH72kE/FqhQVlz2GIYOg8cxyZG xZ5jRzeKrS3UPjDHXfga5NZM2EY8JbOW1mY1JiPbRKu2mjDk1nPA6xC+fmvWsAlm Er3LNvDvH24xjt9eAP7xXglToQNdyw== =aZg/ -----END PGP SIGNATURE----- --g2QTlaeqbOs+6JNr-- 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 5833FE7AD45 for ; Thu, 5 Oct 2023 17:09:57 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qoRqo-000384-A9; Thu, 05 Oct 2023 13:09:26 -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 1qoRqY-0002z5-TW for qemu-devel@nongnu.org; Thu, 05 Oct 2023 13:09:11 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qoRqX-0003NB-7b for qemu-devel@nongnu.org; Thu, 05 Oct 2023 13:09:10 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1696525746; 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: in-reply-to:in-reply-to:references:references; bh=C4OYhYYh6PDU6+Mikb5sio+HPP/8UDtmSicOzQGR2Xk=; b=Ztzk+RR1vg42PaFGulQJPyTtUJ/MyeBv/D3DXRp8VljPt+jA4zbVKPPCxNSWcWIyogr+j9 OORw/tLLbauz7wdgU48dotifzyrHgqUY+RDpXiZf/ipcgtskaxEs+b7cKzqMj10ZNa9h77 QeZKS1zDtej523BcC3K1SUO+jqKe2a0= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-616-kdkb6T-wNySVes5a0WdR_g-1; Thu, 05 Oct 2023 13:08:55 -0400 X-MC-Unique: kdkb6T-wNySVes5a0WdR_g-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id EACDE3C0FC84; Thu, 5 Oct 2023 17:08:54 +0000 (UTC) Received: from localhost (unknown [10.39.192.20]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4996A140E953; Thu, 5 Oct 2023 17:08:54 +0000 (UTC) Date: Thu, 5 Oct 2023 13:08:52 -0400 From: Stefan Hajnoczi To: Hanna Czenczek Cc: qemu-devel@nongnu.org, virtio-fs@redhat.com, "Michael S . Tsirkin" , German Maglione , Eugenio =?iso-8859-1?Q?P=E9rez?= , Anton Kuchin Subject: Re: [PATCH v4 1/8] vhost-user.rst: Deprecate [GS]ET_STATUS Message-ID: <20231005170852.GB1342722@fedora> References: <20231004125904.110781-1-hreitz@redhat.com> <20231004125904.110781-2-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="g2QTlaeqbOs+6JNr" Content-Disposition: inline In-Reply-To: <20231004125904.110781-2-hreitz@redhat.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-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 --g2QTlaeqbOs+6JNr Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Oct 04, 2023 at 02:58:57PM +0200, Hanna Czenczek wrote: > There is no clearly defined purpose for the virtio status byte in > vhost-user: For resetting, we already have RESET_DEVICE; and for virtio > feature negotiation, we have [GS]ET_FEATURES. With the REPLY_ACK > protocol extension, it is possible for SET_FEATURES to return errors > (SET_PROTOCOL_FEATURES may be called before SET_FEATURES). >=20 > As for implementations, SET_STATUS is not widely implemented. dpdk does > implement it, but only uses it to signal feature negotiation failure. > While it does log reset requests (SET_STATUS 0) as such, it effectively > ignores them, in contrast to RESET_OWNER (which is deprecated, and today > means the same thing as RESET_DEVICE). >=20 > While qemu superficially has support for [GS]ET_STATUS, it does not > forward the guest-set status byte, but instead just makes it up > internally, and actually completely ignores what the back-end returns, > only using it as the template for a subsequent SET_STATUS to add single > bits to it. Notably, after setting FEATURES_OK, it never reads it back > to see whether the flag is still set, which is the only way in which > dpdk uses the status byte. >=20 > As-is, no front-end or back-end can rely on the other side handling this > field in a useful manner, and it also provides no practical use over > other mechanisms the vhost-user protocol has, which are more clearly > defined. Deprecate it. >=20 > Suggested-by: Stefan Hajnoczi > Signed-off-by: Hanna Czenczek > --- > docs/interop/vhost-user.rst | 28 +++++++++++++++++++++------- > 1 file changed, 21 insertions(+), 7 deletions(-) Reviewed-by: Stefan Hajnoczi --g2QTlaeqbOs+6JNr Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmUe7aQACgkQnKSrs4Gr c8j32wgAtMdUBKzt8i0RX1vm+5YZjCyIkwymLuqS1sgqzwaa7sFTdEzVUD05tPWQ SCLw+j/yfDHVX0MrCYkMQLuUK6pW9g+tVKVoX34t1p/qYs3L3pikkMzBZARG7iQV 9jLmQJRf5VmXYwkWxfO6KR+sanlLFKgrRQ3rvFJChDMO2nNpuaS5cKtNZYRmlDVe NrOSBleWq1Fkph6tLtV62dNsxcxf48Hm1LUCecOH72kE/FqhQVlz2GIYOg8cxyZG xZ5jRzeKrS3UPjDHXfga5NZM2EY8JbOW1mY1JiPbRKu2mjDk1nPA6xC+fmvWsAlm Er3LNvDvH24xjt9eAP7xXglToQNdyw== =aZg/ -----END PGP SIGNATURE----- --g2QTlaeqbOs+6JNr--