From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 5 Oct 2023 13:48:11 -0400 From: Stefan Hajnoczi Message-ID: <20231005174811.GJ1342722@fedora> References: <20231004125904.110781-1-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="mNw8fgYOgCi8R7Nz" Content-Disposition: inline In-Reply-To: <20231004125904.110781-1-hreitz@redhat.com> Subject: Re: [Virtio-fs] [PATCH v4 0/8] vhost-user: Back-end state migration 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 --mNw8fgYOgCi8R7Nz Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Oct 04, 2023 at 02:58:56PM +0200, Hanna Czenczek wrote: > RFC: > https://lists.nongnu.org/archive/html/qemu-devel/2023-03/msg04263.html >=20 > v1: > https://lists.nongnu.org/archive/html/qemu-devel/2023-04/msg01575.html >=20 > v2: > https://lists.nongnu.org/archive/html/qemu-devel/2023-07/msg02604.html >=20 > v3: > https://lists.nongnu.org/archive/html/qemu-devel/2023-09/msg03750.html >=20 >=20 > Based-on: <20231004014532.1228637-1-stefanha@redhat.com> > ([PATCH v2 0/3] vhost: clean up device reset) >=20 >=20 > Hi, >=20 > This v4 includes largely unchanged patches from v3. The main > addition/change is what came out of the discussion between Stefan and me > around how to proceed without SUSPEND/RESUME, which is that this series > is now based on his reset fix, and it includes more documentation > changes. This looks good. I posted some minor comments on the new patches. Stefan >=20 > Changes in detail: >=20 > - Patch 1: Fall-out from the reset fix: Currently, the status byte is > effectively unused (qemu only uses it for resetting, which all > back-ends ignore; DPDK uses it to announce potential feature > negotiation failure, which qemu ignores). It is also not defined what > exactly front-end or back-end should do with this byte, except > pointing at the virtio spec, which however naturally does not say how > this integrates with vhost-user=E2=80=99s RESET_DEVICE or [GS]ET_FEATUR= ES. > Furthermore, there does not seem to be a use for this; we have > RESET_DEVICE for resetting, and we have [GS]ET_FEATURES (and > REPLY_ACK, which can be used on SET_FEATURES) for feature > negotation. > Therefore, deprecate the status byte, pointing to those other commands > instead. >=20 > - Patch 2: Patch 4 defines a suspended state for the whole back-end if > all vrings are stopped. I think this should be mentioned in > GET_VRING_BASE, but upon trying to add it, I found that it does not > even mention that it stops the vring (mentioned only in the Ring > States section), and remembered that the whole description of both > GET_VRING_BASE and SET_VRING_BASE really was not helpful when trying > to implement a vhost-user back-end. Took the opportunity to overhaul > both. >=20 > - Patch 3: This one=E2=80=99s from v3, but quite heavily modified. Stefan > suggested consistently defining the started/stopped and > enabled/disabled states to be independent, and indeed doing so > simplifies a whole lot of stuff. Specifically, it makes the magic > =E2=80=9Cenabled/disabled when started=E2=80=9D go away. Basically, I = found this > change alone is enough to remove the confusion I had with the existing > documentation. >=20 > - Patch 4: As suggested by Stefan, just define a suspended state without > introducing SUSPEND. vDPA needs SUSPEND because its GET_VRING_BASE > does not stop the vring, but vhost-user=E2=80=99s does, so we can defin= e the > suspended state to be when all vrings are stopped. >=20 > - Patch 5: Reference the suspended state. >=20 > - Patches 6 through 8: Unmodified, except for them being rebase on > Stefan=E2=80=99s series. >=20 >=20 > Hanna Czenczek (8): > vhost-user.rst: Deprecate [GS]ET_STATUS > vhost-user.rst: Improve [GS]ET_VRING_BASE doc > vhost-user.rst: Clarify enabling/disabling vrings > vhost-user.rst: Introduce suspended state > vhost-user.rst: Migrating back-end-internal state > vhost-user: Interface for migration state transfer > vhost: Add high-level state save/load functions > vhost-user-fs: Implement internal migration >=20 > docs/interop/vhost-user.rst | 318 +++++++++++++++++++++++++++--- > include/hw/virtio/vhost-backend.h | 24 +++ > include/hw/virtio/vhost.h | 113 +++++++++++ > hw/virtio/vhost-user-fs.c | 101 +++++++++- > hw/virtio/vhost-user.c | 148 ++++++++++++++ > hw/virtio/vhost.c | 241 ++++++++++++++++++++++ > 6 files changed, 917 insertions(+), 28 deletions(-) >=20 > --=20 > 2.41.0 >=20 --mNw8fgYOgCi8R7Nz Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmUe9tsACgkQnKSrs4Gr c8iA0QgAgmWhPPx/hRn39Jsq3bGeI2mdhbYZbtTE18k2ZdrspkyKPMB45nc8Rj2t zWn/ifLC1tV2UhXYj494uHD4ACPCRv/4KqX16Su1TS3ARcOZcchc9rxmFDN+RrIl faoh+ybFvmDBFFjmbhP4mf/eQeWRttfWEYz9y2TJTOQKMEbpYy/c3PFX8FQrHaz6 +xXW2UvjQ1S2A1zM7XSLWCiAIYO7cVtu5LNFmCkrUAh0fDzui891BteZZaVpYrqB 3Kdee9cnFLhR4+KZRXTkmH7Q1VHZoJRxWhcyLURlx/9YZ5bkx/1wLUQYo8+m12Qm iuKHpsTjElpLmFqGG00n1C9uoOYEUQ== =TZJp -----END PGP SIGNATURE----- --mNw8fgYOgCi8R7Nz-- 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 5C91FE92721 for ; Thu, 5 Oct 2023 17:48:38 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qoSSS-0000VK-BD; Thu, 05 Oct 2023 13:48:20 -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 1qoSSQ-0000Us-N4 for qemu-devel@nongnu.org; Thu, 05 Oct 2023 13:48:18 -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 1qoSSO-0005qH-E6 for qemu-devel@nongnu.org; Thu, 05 Oct 2023 13:48:18 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1696528095; 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=ECP7IDOEDTjkevFHFfuJxtdaOfQHpXJehiYmyPZnBdM=; b=dh69TEpALVSHh+hX0kumad07CYCh0hGB/e5saDQwrxeL6jc5WlxX8R9Xg6xAFFb26V0PcK z4hHFEpM5ehUdvjjaaGsw1cC67W6+XDf9cKIQUansMBfG4e71bpG9X0NLC1bKZOYWXRARL 1LLRB4rlLl7CDiSRJ4Ym+nV+FNuZzQo= 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-508-WNZz_MqgNGaZ2RRm59UHdw-1; Thu, 05 Oct 2023 13:48:13 -0400 X-MC-Unique: WNZz_MqgNGaZ2RRm59UHdw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (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 139122810D51; Thu, 5 Oct 2023 17:48:13 +0000 (UTC) Received: from localhost (unknown [10.39.192.20]) by smtp.corp.redhat.com (Postfix) with ESMTP id 80F4A10F1BE7; Thu, 5 Oct 2023 17:48:12 +0000 (UTC) Date: Thu, 5 Oct 2023 13:48:11 -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 0/8] vhost-user: Back-end state migration Message-ID: <20231005174811.GJ1342722@fedora> References: <20231004125904.110781-1-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="mNw8fgYOgCi8R7Nz" Content-Disposition: inline In-Reply-To: <20231004125904.110781-1-hreitz@redhat.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 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 --mNw8fgYOgCi8R7Nz Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Oct 04, 2023 at 02:58:56PM +0200, Hanna Czenczek wrote: > RFC: > https://lists.nongnu.org/archive/html/qemu-devel/2023-03/msg04263.html >=20 > v1: > https://lists.nongnu.org/archive/html/qemu-devel/2023-04/msg01575.html >=20 > v2: > https://lists.nongnu.org/archive/html/qemu-devel/2023-07/msg02604.html >=20 > v3: > https://lists.nongnu.org/archive/html/qemu-devel/2023-09/msg03750.html >=20 >=20 > Based-on: <20231004014532.1228637-1-stefanha@redhat.com> > ([PATCH v2 0/3] vhost: clean up device reset) >=20 >=20 > Hi, >=20 > This v4 includes largely unchanged patches from v3. The main > addition/change is what came out of the discussion between Stefan and me > around how to proceed without SUSPEND/RESUME, which is that this series > is now based on his reset fix, and it includes more documentation > changes. This looks good. I posted some minor comments on the new patches. Stefan >=20 > Changes in detail: >=20 > - Patch 1: Fall-out from the reset fix: Currently, the status byte is > effectively unused (qemu only uses it for resetting, which all > back-ends ignore; DPDK uses it to announce potential feature > negotiation failure, which qemu ignores). It is also not defined what > exactly front-end or back-end should do with this byte, except > pointing at the virtio spec, which however naturally does not say how > this integrates with vhost-user=E2=80=99s RESET_DEVICE or [GS]ET_FEATUR= ES. > Furthermore, there does not seem to be a use for this; we have > RESET_DEVICE for resetting, and we have [GS]ET_FEATURES (and > REPLY_ACK, which can be used on SET_FEATURES) for feature > negotation. > Therefore, deprecate the status byte, pointing to those other commands > instead. >=20 > - Patch 2: Patch 4 defines a suspended state for the whole back-end if > all vrings are stopped. I think this should be mentioned in > GET_VRING_BASE, but upon trying to add it, I found that it does not > even mention that it stops the vring (mentioned only in the Ring > States section), and remembered that the whole description of both > GET_VRING_BASE and SET_VRING_BASE really was not helpful when trying > to implement a vhost-user back-end. Took the opportunity to overhaul > both. >=20 > - Patch 3: This one=E2=80=99s from v3, but quite heavily modified. Stefan > suggested consistently defining the started/stopped and > enabled/disabled states to be independent, and indeed doing so > simplifies a whole lot of stuff. Specifically, it makes the magic > =E2=80=9Cenabled/disabled when started=E2=80=9D go away. Basically, I = found this > change alone is enough to remove the confusion I had with the existing > documentation. >=20 > - Patch 4: As suggested by Stefan, just define a suspended state without > introducing SUSPEND. vDPA needs SUSPEND because its GET_VRING_BASE > does not stop the vring, but vhost-user=E2=80=99s does, so we can defin= e the > suspended state to be when all vrings are stopped. >=20 > - Patch 5: Reference the suspended state. >=20 > - Patches 6 through 8: Unmodified, except for them being rebase on > Stefan=E2=80=99s series. >=20 >=20 > Hanna Czenczek (8): > vhost-user.rst: Deprecate [GS]ET_STATUS > vhost-user.rst: Improve [GS]ET_VRING_BASE doc > vhost-user.rst: Clarify enabling/disabling vrings > vhost-user.rst: Introduce suspended state > vhost-user.rst: Migrating back-end-internal state > vhost-user: Interface for migration state transfer > vhost: Add high-level state save/load functions > vhost-user-fs: Implement internal migration >=20 > docs/interop/vhost-user.rst | 318 +++++++++++++++++++++++++++--- > include/hw/virtio/vhost-backend.h | 24 +++ > include/hw/virtio/vhost.h | 113 +++++++++++ > hw/virtio/vhost-user-fs.c | 101 +++++++++- > hw/virtio/vhost-user.c | 148 ++++++++++++++ > hw/virtio/vhost.c | 241 ++++++++++++++++++++++ > 6 files changed, 917 insertions(+), 28 deletions(-) >=20 > --=20 > 2.41.0 >=20 --mNw8fgYOgCi8R7Nz Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmUe9tsACgkQnKSrs4Gr c8iA0QgAgmWhPPx/hRn39Jsq3bGeI2mdhbYZbtTE18k2ZdrspkyKPMB45nc8Rj2t zWn/ifLC1tV2UhXYj494uHD4ACPCRv/4KqX16Su1TS3ARcOZcchc9rxmFDN+RrIl faoh+ybFvmDBFFjmbhP4mf/eQeWRttfWEYz9y2TJTOQKMEbpYy/c3PFX8FQrHaz6 +xXW2UvjQ1S2A1zM7XSLWCiAIYO7cVtu5LNFmCkrUAh0fDzui891BteZZaVpYrqB 3Kdee9cnFLhR4+KZRXTkmH7Q1VHZoJRxWhcyLURlx/9YZ5bkx/1wLUQYo8+m12Qm iuKHpsTjElpLmFqGG00n1C9uoOYEUQ== =TZJp -----END PGP SIGNATURE----- --mNw8fgYOgCi8R7Nz--