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Tsirkin" Subject: Re: [RFC PATCH v2 2/5] vhost_user: Add frontend command for shmem config Message-ID: <20240711081553.GA572069@dynamic-pd01.res.v6.highway.a1.net> References: <20240628145710.1516121-1-aesteve@redhat.com> <20240628145710.1516121-3-aesteve@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="A+seTadtYhm8vzwx" Content-Disposition: inline In-Reply-To: <20240628145710.1516121-3-aesteve@redhat.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 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: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.144, 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 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 --A+seTadtYhm8vzwx Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Jun 28, 2024 at 04:57:07PM +0200, Albert Esteve wrote: > The frontend can use this command to retrieve > VIRTIO Shared Memory Regions configuration from > the backend. The response contains the number of > shared memory regions, their size, and shmid. >=20 > This is useful when the frontend is unaware of > specific backend type and configuration, > for example, in the `vhost-user-device` case. >=20 > Signed-off-by: Albert Esteve > --- > docs/interop/vhost-user.rst | 31 +++++++++++++++++++++++ > hw/virtio/vhost-user.c | 42 +++++++++++++++++++++++++++++++ > include/hw/virtio/vhost-backend.h | 6 +++++ > include/hw/virtio/vhost-user.h | 1 + > 4 files changed, 80 insertions(+) >=20 > diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst > index d52ba719d5..51f01d1d84 100644 > --- a/docs/interop/vhost-user.rst > +++ b/docs/interop/vhost-user.rst > @@ -348,6 +348,19 @@ Device state transfer parameters > In the future, additional phases might be added e.g. to allow > iterative migration while the device is running. > =20 > +VIRTIO Shared Memory Region configuration > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > + > ++-------------+---------+------------+----+------------+ > +| num regions | padding | mem size 0 | .. | mem size 7 | > ++-------------+---------+------------+----+------------+ > + > +:num regions: a 32-bit number of regions > + > +:padding: 32-bit > + > +:mem size: 64-bit size of VIRTIO Shared Memory Region > + > C structure > ----------- > =20 > @@ -369,6 +382,10 @@ In QEMU the vhost-user message is implemented with t= he following struct: > VhostUserConfig config; > VhostUserVringArea area; > VhostUserInflight inflight; > + VhostUserShared object; > + VhostUserTransferDeviceState transfer_state; > + VhostUserMMap mmap; > + VhostUserShMemConfig shmem; > }; > } QEMU_PACKED VhostUserMsg; > =20 > @@ -1051,6 +1068,7 @@ Protocol features > #define VHOST_USER_PROTOCOL_F_XEN_MMAP 17 > #define VHOST_USER_PROTOCOL_F_SHARED_OBJECT 18 > #define VHOST_USER_PROTOCOL_F_DEVICE_STATE 19 > + #define VHOST_USER_PROTOCOL_F_SHMEM 20 > =20 > Front-end message types > ----------------------- > @@ -1725,6 +1743,19 @@ Front-end message types > Using this function requires prior negotiation of the > ``VHOST_USER_PROTOCOL_F_DEVICE_STATE`` feature. > =20 > +``VHOST_USER_GET_SHMEM_CONFIG`` > + :id: 44 > + :equivalent ioctl: N/A > + :request payload: N/A > + :reply payload: ``struct VhostUserShMemConfig`` > + > + When the ``VHOST_USER_PROTOCOL_F_SHMEM`` protocol feature has been > + successfully negotiated, this message can be submitted by the front-end > + to gather the VIRTIO Shared Memory Region configuration. Back-end will= respond > + with the number of VIRTIO Shared Memory Regions it requires, and each = shared memory > + region size in an array. The shared memory IDs are represented by the = index > + of the array. Please add: - The Shared Memory Region size must be a multiple of the page size support= ed by mmap(2). - The size may be 0 if the region is unused. 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