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Wed, 8 Nov 2023 10:30:56 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.193.56]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 17B05492BFA; Wed, 8 Nov 2023 10:30:56 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id DF58921E6A1F; Wed, 8 Nov 2023 11:30:53 +0100 (CET) From: Markus Armbruster To: =?utf-8?Q?C=C3=A9dric?= Le Goater Cc: Zhenzhong Duan , qemu-devel@nongnu.org, alex.williamson@redhat.com, jgg@nvidia.com, nicolinc@nvidia.com, joao.m.martins@oracle.com, eric.auger@redhat.com, peterx@redhat.com, jasowang@redhat.com, kevin.tian@intel.com, yi.l.liu@intel.com, yi.y.sun@intel.com, chao.p.peng@intel.com, Paolo Bonzini , Eric Blake , Daniel P. =?utf-8?Q?Berrang=C3=A9?= , Eduardo Habkost , Thomas Huth Subject: Re: [PATCH v4 26/41] backends/iommufd: Introduce the iommufd object References: <20231102071302.1818071-1-zhenzhong.duan@intel.com> <20231102071302.1818071-27-zhenzhong.duan@intel.com> <87r0l0dc9q.fsf@pond.sub.org> Date: Wed, 08 Nov 2023 11:30:53 +0100 In-Reply-To: (=?utf-8?Q?=22C=C3=A9dric?= Le Goater"'s message of "Wed, 8 Nov 2023 11:03:45 +0100") Message-ID: <87zfzoa65e.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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 C=C3=A9dric Le Goater writes: > Hello Markus, > > On 11/8/23 06:50, Markus Armbruster wrote: >> C=C3=A9dric Le Goater writes: >>=20 >>> On 11/2/23 08:12, Zhenzhong Duan wrote: >>>> From: Eric Auger >>>> Introduce an iommufd object which allows the interaction >>>> with the host /dev/iommu device. >>>> The /dev/iommu can have been already pre-opened outside of qemu, >>>> in which case the fd can be passed directly along with the >>>> iommufd object: >>>> This allows the iommufd object to be shared accross several >>>> subsystems (VFIO, VDPA, ...). For example, libvirt would open >>>> the /dev/iommu once. >>>> If no fd is passed along with the iommufd object, the /dev/iommu >>>> is opened by the qemu code. >>>> The CONFIG_IOMMUFD option must be set to compile this new object. >>>> Suggested-by: Alex Williamson >>>> Signed-off-by: Eric Auger >>>> Signed-off-by: Yi Liu >>>> Signed-off-by: Zhenzhong Duan >>>> --- >>>> v4: add CONFIG_IOMMUFD check, document default case >>>> MAINTAINERS | 7 ++ >>>> qapi/qom.json | 22 ++++ >>>> include/sysemu/iommufd.h | 46 +++++++ >>>> backends/iommufd-stub.c | 59 +++++++++ >>>> backends/iommufd.c | 257 ++++++++++++++++++++++++++++++++++++= +++ >>>> backends/Kconfig | 4 + >>>> backends/meson.build | 5 + >>>> backends/trace-events | 12 ++ >>>> qemu-options.hx | 13 ++ >>>> 9 files changed, 425 insertions(+) >>>> create mode 100644 include/sysemu/iommufd.h >>>> create mode 100644 backends/iommufd-stub.c >>>> create mode 100644 backends/iommufd.c >>>> diff --git a/MAINTAINERS b/MAINTAINERS >>>> index cd8d6b140f..6f35159255 100644 >>>> --- a/MAINTAINERS >>>> +++ b/MAINTAINERS >>>> @@ -2135,6 +2135,13 @@ F: hw/vfio/ap.c >>>> F: docs/system/s390x/vfio-ap.rst >>>> L: qemu-s390x@nongnu.org >>>> +iommufd >>>> +M: Yi Liu >>>> +M: Eric Auger >>>> +S: Supported >>>> +F: backends/iommufd.c >>>> +F: include/sysemu/iommufd.h >>>> + >>>> vhost >>>> M: Michael S. Tsirkin >>>> S: Supported >>>> diff --git a/qapi/qom.json b/qapi/qom.json >>>> index c53ef978ff..27300add48 100644 >>>> --- a/qapi/qom.json >>>> +++ b/qapi/qom.json >>>> @@ -794,6 +794,24 @@ >>>> { 'struct': 'VfioUserServerProperties', >>>> 'data': { 'socket': 'SocketAddress', 'device': 'str' } } >>>> +## >>>> +# @IOMMUFDProperties: >>>> +# >>>> +# Properties for iommufd objects. >>>> +# >>>> +# @fd: file descriptor name previously passed via 'getfd' command, >>>> +# which represents a pre-opened /dev/iommu. This allows the >>>> +# iommufd object to be shared accross several subsystems >>>> +# (VFIO, VDPA, ...), and the file descriptor to be shared >>>> +# with other process, e.g. DPDK. (default: QEMU opens >>>> +# /dev/iommu by itself) >>>> +# >>>> +# Since: 8.2 >>>> +## >>>> +{ 'struct': 'IOMMUFDProperties', >>>> + 'data': { '*fd': 'str' }, >>>> + 'if': 'CONFIG_IOMMUFD' } >>> >>> >>> Activating or not IOMMUFD on a platform is a configuration choice >>> and it is not a dependency on an external resource. I would make >>> things simpler and drop all the #ifdef in the documentation files. >> >> What exactly are you proposing? > > I would like to simplify the configuration part of this new IOMMUFD > feature and avoid a ./configure option to enable/disable the feature > since it has no external dependencies and can be compiled on all > platforms. > > However, we know that it only makes sense to have the IOMMUFD backend > on platforms s390x, aarch64, x86_64. So I am proposing as an improvement > to enable IOMMUFD only on these platforms with this addition : > > imply IOMMUFD > > to hw/{i386,s390x,arm}/Kconfig files. > > This gives us the possibility to compile out the feature downstream > if something goes wrong, using the files under : configs/devices/. Shouldn't we then compile out the relevant parts of the QAPI schema, too? > Given that the IOMMUFD feature doesn't have any external dependencies > and that the IOMMUFD backend object is common to all platforms, I am > also proposing to remove all the CONFIG_IOMMUFD define usage in the > documentation file "qemu-options.hx" and the schema file "qapi/qom.json". Any CONFIG_IOMMUFD left elsewhere? >> The use of 'if': 'CONFIG_IOMMUFD' in the QAPI schema enables >> introspection with query-qmp-schema: when ObjectType @iommufd exists, >> QEMU supports creating the object. Or am I confused? > > Object iommufd should always exist since it is common to all. > > Is that acceptable ? Perhaps the question to ask is whether a management application needs to know whether this version of QEMU supports iommufd objects. If yes, then query-qmp-schema is an obvious way to find out. What could go wrong when this returns "supported" when it actually isn't?