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 65722CA0EE4 for ; Mon, 18 Aug 2025 20:42:53 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uo6g3-0006Rs-Jg; Mon, 18 Aug 2025 16:41:59 -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 1uo6g1-0006Rj-W8 for qemu-devel@nongnu.org; Mon, 18 Aug 2025 16:41:58 -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 1uo6fy-0005up-Eo for qemu-devel@nongnu.org; Mon, 18 Aug 2025 16:41:57 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1755549713; 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=0Xh5JlwKBgC43XJoZz8O53ukH36umxN+faQ35BLYHNU=; b=i2A1z/7klTWMuz02sVueAU/sJHZL62c+mkYJjbBOd241SS+I/r7Lta5bAliujV9acU545l qhRazoTWaqZM6n2/QIFUPUGf7sjEr7ww7d/n47y0uj4WblZuLvaM19SLuObwBuACu0YJDn GCp7gOwLC2dRGP11sCsmU9pHErRuwqI= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-14-4Hz1URxEPfSkHfjqUW_KjQ-1; Mon, 18 Aug 2025 16:41:50 -0400 X-MC-Unique: 4Hz1URxEPfSkHfjqUW_KjQ-1 X-Mimecast-MFC-AGG-ID: 4Hz1URxEPfSkHfjqUW_KjQ_1755549709 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 563D919775D8; Mon, 18 Aug 2025 20:41:49 +0000 (UTC) Received: from localhost (unknown [10.2.16.66]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 0DA791955F24; Mon, 18 Aug 2025 20:41:46 +0000 (UTC) Date: Mon, 18 Aug 2025 14:58:16 -0400 From: Stefan Hajnoczi To: Albert Esteve Cc: qemu-devel@nongnu.org, david@redhat.com, "Michael S. Tsirkin" , hi@alyssa.is, jasowang@redhat.com, Laurent Vivier , dbassey@redhat.com, Stefano Garzarella , Paolo Bonzini , stevensd@chromium.org, Fabiano Rosas , Alex =?iso-8859-1?Q?Benn=E9e?= , slp@redhat.com Subject: Re: [PATCH v7 1/8] vhost-user: Add VirtIO Shared Memory map request Message-ID: <20250818185816.GB16685@fedora> References: <20250818100353.1560655-1-aesteve@redhat.com> <20250818100353.1560655-2-aesteve@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="ZwZCyUvPYykV+HTW" Content-Disposition: inline In-Reply-To: <20250818100353.1560655-2-aesteve@redhat.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-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 --ZwZCyUvPYykV+HTW Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Aug 18, 2025 at 12:03:46PM +0200, Albert Esteve wrote: (I haven't fully reviewed this yet, but here are my current comments.) > Add SHMEM_MAP/UNMAP requests to vhost-user for > dynamic management of VIRTIO Shared Memory mappings. >=20 > This implementation introduces VhostUserShmemObject > as an intermediate QOM parent for MemoryRegions > created for SHMEM_MAP requests. This object > provides reference-counted lifecycle management > with automatic cleanup. >=20 > This request allows backends to dynamically map > file descriptors into a VIRTIO Shared Memory > Regions identified by their shmid. Maps are created > using memory_region_init_ram_device_ptr() with > configurable read/write permissions, and the resulting > MemoryRegions are added as subregions to the shmem > container region. The mapped memory is then advertised > to the guest VIRTIO drivers as a base address plus > offset for reading and writting according > to the requested mmap flags. >=20 > The backend can unmap memory ranges within a given > VIRTIO Shared Memory Region to free resources. > Upon receiving this message, the frontend removes > the MemoryRegion as a subregion and automatically > unreferences the associated VhostUserShmemObject, > triggering cleanup if no other references exist. >=20 > Error handling has been improved to ensure consistent > behavior across handlers that manage their own > vhost_user_send_resp() calls. Since these handlers > clear the VHOST_USER_NEED_REPLY_MASK flag, explicit > error checking ensures proper connection closure on > failures, maintaining the expected error flow. >=20 > Note the memory region commit for these > operations needs to be delayed until after we > respond to the backend to avoid deadlocks. >=20 > Signed-off-by: Albert Esteve > --- > hw/virtio/meson.build | 1 + > hw/virtio/vhost-user-shmem.c | 134 ++++++++++++++ > hw/virtio/vhost-user.c | 207 +++++++++++++++++++++- > hw/virtio/virtio.c | 109 ++++++++++++ > include/hw/virtio/vhost-user-shmem.h | 75 ++++++++ > include/hw/virtio/virtio.h | 93 ++++++++++ > subprojects/libvhost-user/libvhost-user.c | 70 ++++++++ > subprojects/libvhost-user/libvhost-user.h | 54 ++++++ > 8 files changed, 741 insertions(+), 2 deletions(-) > create mode 100644 hw/virtio/vhost-user-shmem.c > create mode 100644 include/hw/virtio/vhost-user-shmem.h >=20 > diff --git a/hw/virtio/meson.build b/hw/virtio/meson.build > index 3ea7b3cec8..5efcf70b75 100644 > --- a/hw/virtio/meson.build > +++ b/hw/virtio/meson.build > @@ -20,6 +20,7 @@ if have_vhost > # fixme - this really should be generic > specific_virtio_ss.add(files('vhost-user.c')) > system_virtio_ss.add(files('vhost-user-base.c')) > + system_virtio_ss.add(files('vhost-user-shmem.c')) > =20 > # MMIO Stubs > system_virtio_ss.add(files('vhost-user-device.c')) > diff --git a/hw/virtio/vhost-user-shmem.c b/hw/virtio/vhost-user-shmem.c > new file mode 100644 > index 0000000000..1d763b56b6 > --- /dev/null > +++ b/hw/virtio/vhost-user-shmem.c > @@ -0,0 +1,134 @@ > +/* > + * VHost-user Shared Memory Object > + * > + * Copyright Red Hat, Inc. 2025 > + * > + * Authors: > + * Albert Esteve > + * > + * This work is licensed under the terms of the GNU GPL, version 2 or la= ter. > + * See the COPYING file in the top-level directory. > + */ > + > +#include "qemu/osdep.h" > +#include "hw/virtio/vhost-user-shmem.h" > +#include "system/memory.h" > +#include "qapi/error.h" > +#include "qemu/error-report.h" > +#include "trace.h" > + > +/** > + * VhostUserShmemObject > + * > + * An intermediate QOM object that manages individual shared memory mapp= ings > + * created by VHOST_USER_BACKEND_SHMEM_MAP requests. It acts as a parent= for > + * MemoryRegion objects, providing proper lifecycle management with refe= rence > + * counting. When the object is unreferenced and its reference count dro= ps > + * to zero, it automatically cleans up the MemoryRegion and unmaps the m= emory. > + */ > + > +static void vhost_user_shmem_object_finalize(Object *obj); > +static void vhost_user_shmem_object_instance_init(Object *obj); > + > +static const TypeInfo vhost_user_shmem_object_info =3D { > + .name =3D TYPE_VHOST_USER_SHMEM_OBJECT, > + .parent =3D TYPE_OBJECT, > + .instance_size =3D sizeof(VhostUserShmemObject), > + .instance_init =3D vhost_user_shmem_object_instance_init, > + .instance_finalize =3D vhost_user_shmem_object_finalize, > +}; > + > +static void vhost_user_shmem_object_instance_init(Object *obj) > +{ > + VhostUserShmemObject *shmem_obj =3D VHOST_USER_SHMEM_OBJECT(obj); > + > + shmem_obj->shmid =3D 0; > + shmem_obj->fd =3D -1; > + shmem_obj->shm_offset =3D 0; > + shmem_obj->len =3D 0; > + shmem_obj->mr =3D NULL; > +} > + > +static void vhost_user_shmem_object_finalize(Object *obj) > +{ > + VhostUserShmemObject *shmem_obj =3D VHOST_USER_SHMEM_OBJECT(obj); > + > + /* Clean up MemoryRegion if it exists */ > + if (shmem_obj->mr) { > + /* Unparent the MemoryRegion to trigger cleanup */ > + object_unparent(OBJECT(shmem_obj->mr)); > + shmem_obj->mr =3D NULL; > + } > + > + /* Close file descriptor */ > + if (shmem_obj->fd >=3D 0) { > + close(shmem_obj->fd); > + shmem_obj->fd =3D -1; > + } > +} > + > +VhostUserShmemObject *vhost_user_shmem_object_new(uint8_t shmid, > + int fd, > + uint64_t fd_offset, > + uint64_t shm_offset, > + uint64_t len, > + uint16_t flags) > +{ > + VhostUserShmemObject *shmem_obj; > + MemoryRegion *mr; > + g_autoptr(GString) mr_name =3D g_string_new(NULL); > + uint32_t ram_flags; > + Error *local_err =3D NULL; > + > + if (len =3D=3D 0) { > + error_report("Shared memory mapping size cannot be zero"); > + return NULL; > + } > + > + fd =3D dup(fd); > + if (fd < 0) { > + error_report("Failed to duplicate fd: %s", strerror(errno)); > + return NULL; > + } > + > + /* Determine RAM flags */ > + ram_flags =3D RAM_SHARED; > + if (!(flags & VHOST_USER_FLAG_MAP_RW)) { > + ram_flags |=3D RAM_READONLY_FD; > + } > + > + /* Create the VhostUserShmemObject */ > + shmem_obj =3D VHOST_USER_SHMEM_OBJECT( > + object_new(TYPE_VHOST_USER_SHMEM_OBJECT)); > + > + /* Set up object properties */ > + shmem_obj->shmid =3D shmid; > + shmem_obj->fd =3D fd; > + shmem_obj->shm_offset =3D shm_offset; > + shmem_obj->len =3D len; > + > + /* Create MemoryRegion as a child of this object */ > + mr =3D g_new0(MemoryRegion, 1); > + g_string_printf(mr_name, "vhost-user-shmem-%d-%" PRIx64, shmid, shm_= offset); > + > + /* Initialize MemoryRegion with file descriptor */ > + if (!memory_region_init_ram_from_fd(mr, OBJECT(shmem_obj), mr_name->= str, > + len, ram_flags, fd, fd_offset, > + &local_err)) { > + error_report_err(local_err); > + g_free(mr); > + close(fd); > + object_unref(OBJECT(shmem_obj)); > + return NULL; > + } > + > + shmem_obj->mr =3D mr; > + return shmem_obj; > +} > + > +static void vhost_user_shmem_register_types(void) > +{ > + type_register_static(&vhost_user_shmem_object_info); > +} > + > +type_init(vhost_user_shmem_register_types) > diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c > index 1e1d6b0d6e..eb3ad728b0 100644 > --- a/hw/virtio/vhost-user.c > +++ b/hw/virtio/vhost-user.c > @@ -11,6 +11,7 @@ > #include "qemu/osdep.h" > #include "qapi/error.h" > #include "hw/virtio/virtio-dmabuf.h" > +#include "hw/virtio/vhost-user-shmem.h" > #include "hw/virtio/vhost.h" > #include "hw/virtio/virtio-crypto.h" > #include "hw/virtio/vhost-user.h" > @@ -115,6 +116,8 @@ typedef enum VhostUserBackendRequest { > VHOST_USER_BACKEND_SHARED_OBJECT_ADD =3D 6, > VHOST_USER_BACKEND_SHARED_OBJECT_REMOVE =3D 7, > VHOST_USER_BACKEND_SHARED_OBJECT_LOOKUP =3D 8, > + VHOST_USER_BACKEND_SHMEM_MAP =3D 9, > + VHOST_USER_BACKEND_SHMEM_UNMAP =3D 10, > VHOST_USER_BACKEND_MAX > } VhostUserBackendRequest; > =20 > @@ -192,6 +195,23 @@ typedef struct VhostUserShared { > unsigned char uuid[16]; > } VhostUserShared; > =20 > +/* For the flags field of VhostUserMMap */ > +#define VHOST_USER_FLAG_MAP_RW (1u << 0) > + > +typedef struct { > + /* VIRTIO Shared Memory Region ID */ > + uint8_t shmid; > + uint8_t padding[7]; > + /* File offset */ > + uint64_t fd_offset; > + /* Offset within the VIRTIO Shared Memory Region */ > + uint64_t shm_offset; > + /* Size of the mapping */ > + uint64_t len; > + /* Flags for the mmap operation, from VHOST_USER_FLAG_MAP_* */ > + uint16_t flags; > +} VhostUserMMap; > + > typedef struct { > VhostUserRequest request; > =20 > @@ -224,6 +244,7 @@ typedef union { > VhostUserInflight inflight; > VhostUserShared object; > VhostUserTransferDeviceState transfer_state; > + VhostUserMMap mmap; > } VhostUserPayload; > =20 > typedef struct VhostUserMsg { > @@ -1768,6 +1789,172 @@ vhost_user_backend_handle_shared_object_lookup(st= ruct vhost_user *u, > return 0; > } > =20 > +/** > + * vhost_user_backend_handle_shmem_map() - Handle SHMEM_MAP backend requ= est > + * @dev: vhost device > + * @ioc: QIOChannel for communication > + * @hdr: vhost-user message header > + * @payload: message payload containing mapping details > + * @fd: file descriptor for the shared memory region > + * > + * Handles VHOST_USER_BACKEND_SHMEM_MAP requests from the backend. Creat= es > + * a VhostUserShmemObject to manage the shared memory mapping and adds it > + * to the appropriate VirtIO shared memory region. The VhostUserShmemObj= ect > + * serves as an intermediate parent for the MemoryRegion, ensuring proper > + * lifecycle management with reference counting. > + * > + * Returns: 0 on success, negative errno on failure > + */ > +static int > +vhost_user_backend_handle_shmem_map(struct vhost_dev *dev, > + QIOChannel *ioc, > + VhostUserHeader *hdr, > + VhostUserPayload *payload, > + int fd) > +{ > + VirtioSharedMemory *shmem; > + VhostUserMMap *vu_mmap =3D &payload->mmap; > + Error *local_err =3D NULL; > + g_autoptr(GString) shm_name =3D g_string_new(NULL); > + > + if (fd < 0) { > + error_report("Bad fd for map"); > + return -EBADF; > + } > + > + if (QSIMPLEQ_EMPTY(&dev->vdev->shmem_list)) { > + error_report("Device has no VIRTIO Shared Memory Regions. " > + "Requested ID: %d", vu_mmap->shmid); > + return -EFAULT; > + } > + > + shmem =3D virtio_find_shmem_region(dev->vdev, vu_mmap->shmid); > + if (!shmem) { > + error_report("VIRTIO Shared Memory Region at " > + "ID %d not found or unitialized", vu_mmap->shmid); > + return -EFAULT; > + } > + > + if ((vu_mmap->shm_offset + vu_mmap->len) < vu_mmap->len || > + (vu_mmap->shm_offset + vu_mmap->len) > shmem->mr.size) { > + error_report("Bad offset/len for mmap %" PRIx64 "+%" PRIx64, > + vu_mmap->shm_offset, vu_mmap->len); > + return -EFAULT; > + } > + > + g_string_printf(shm_name, "virtio-shm%i-%lu", > + vu_mmap->shmid, vu_mmap->shm_offset); > + > + memory_region_transaction_begin(); > + > + /* Create VhostUserShmemObject as intermediate parent for MemoryRegi= on */ > + VhostUserShmemObject *shmem_obj =3D vhost_user_shmem_object_new( > + vu_mmap->shmid, fd, vu_mmap->fd_offset, vu_mmap->shm_offset, > + vu_mmap->len, vu_mmap->flags); > + > + if (!shmem_obj) { > + memory_region_transaction_commit(); > + return -EFAULT; > + } > + > + /* Add the mapping using our VhostUserShmemObject as the parent */ > + if (virtio_add_shmem_map(shmem, shmem_obj) !=3D 0) { > + error_report("Failed to add shared memory mapping"); > + object_unref(OBJECT(shmem_obj)); > + memory_region_transaction_commit(); > + return -EFAULT; > + } > + > + if (hdr->flags & VHOST_USER_NEED_REPLY_MASK) { > + payload->u64 =3D 0; > + hdr->size =3D sizeof(payload->u64); > + vhost_user_send_resp(ioc, hdr, payload, &local_err); > + if (local_err) { > + error_report_err(local_err); > + memory_region_transaction_commit(); > + return -EFAULT; > + } > + } > + > + memory_region_transaction_commit(); > + > + return 0; > +} > + > +/** > + * vhost_user_backend_handle_shmem_unmap() - Handle SHMEM_UNMAP backend = request > + * @dev: vhost device > + * @ioc: QIOChannel for communication > + * @hdr: vhost-user message header > + * @payload: message payload containing unmapping details > + * > + * Handles VHOST_USER_BACKEND_SHMEM_UNMAP requests from the backend. Rem= oves > + * the specified memory mapping from the VirtIO shared memory region. Th= is > + * automatically unreferences the associated VhostUserShmemObject, which= may > + * trigger its finalization and cleanup (munmap, close fd) if no other > + * references exist. > + * > + * Returns: 0 on success, negative errno on failure > + */ > +static int > +vhost_user_backend_handle_shmem_unmap(struct vhost_dev *dev, > + QIOChannel *ioc, > + VhostUserHeader *hdr, > + VhostUserPayload *payload) > +{ > + VirtioSharedMemory *shmem; > + VirtioSharedMemoryMapping *mmap =3D NULL; > + VhostUserMMap *vu_mmap =3D &payload->mmap; > + Error *local_err =3D NULL; > + > + if (QSIMPLEQ_EMPTY(&dev->vdev->shmem_list)) { > + error_report("Device has no VIRTIO Shared Memory Regions. " > + "Requested ID: %d", vu_mmap->shmid); > + return -EFAULT; > + } > + > + shmem =3D virtio_find_shmem_region(dev->vdev, vu_mmap->shmid); > + if (!shmem) { > + error_report("VIRTIO Shared Memory Region at " > + "ID %d not found or unitialized", vu_mmap->shmid); > + return -EFAULT; > + } > + > + if ((vu_mmap->shm_offset + vu_mmap->len) < vu_mmap->len || > + (vu_mmap->shm_offset + vu_mmap->len) > shmem->mr.size) { > + error_report("Bad offset/len for unmmap %" PRIx64 "+%" PRIx64, > + vu_mmap->shm_offset, vu_mmap->len); > + return -EFAULT; > + } > + > + mmap =3D virtio_find_shmem_map(shmem, vu_mmap->shm_offset, vu_mmap->= len); > + if (!mmap) { > + error_report("Shared memory mapping not found at offset %" PRIx64 > + " with length %" PRIx64, > + vu_mmap->shm_offset, vu_mmap->len); > + return -EFAULT; > + } > + > + memory_region_transaction_begin(); > + memory_region_del_subregion(&shmem->mr, mmap->mem); > + if (hdr->flags & VHOST_USER_NEED_REPLY_MASK) { > + payload->u64 =3D 0; > + hdr->size =3D sizeof(payload->u64); > + vhost_user_send_resp(ioc, hdr, payload, &local_err); > + if (local_err) { > + error_report_err(local_err); > + memory_region_transaction_commit(); > + return -EFAULT; > + } > + } > + memory_region_transaction_commit(); > + > + /* Free the MemoryRegion only after vhost_commit */ > + virtio_del_shmem_map(shmem, vu_mmap->shm_offset, vu_mmap->len); > + > + return 0; > +} > + > static void close_backend_channel(struct vhost_user *u) > { > g_source_destroy(u->backend_src); > @@ -1833,8 +2020,24 @@ static gboolean backend_read(QIOChannel *ioc, GIOC= ondition condition, > &payload.ob= ject); > break; > case VHOST_USER_BACKEND_SHARED_OBJECT_LOOKUP: > - ret =3D vhost_user_backend_handle_shared_object_lookup(dev->opaq= ue, ioc, > - &hdr, &payl= oad); > + /* Handler manages its own response, check error and close conne= ction */ > + if (vhost_user_backend_handle_shared_object_lookup(dev->opaque, = ioc, > + &hdr, &payloa= d) < 0) { > + goto err; > + } > + break; > + case VHOST_USER_BACKEND_SHMEM_MAP: > + /* Handler manages its own response, check error and close conne= ction */ > + if (vhost_user_backend_handle_shmem_map(dev, ioc, &hdr, &payload, > + fd ? fd[0] : -1) < 0) { > + goto err; > + } > + break; > + case VHOST_USER_BACKEND_SHMEM_UNMAP: > + /* Handler manages its own response, check error and close conne= ction */ > + if (vhost_user_backend_handle_shmem_unmap(dev, ioc, &hdr, &paylo= ad) < 0) { > + goto err; > + } > break; > default: > error_report("Received unexpected msg type: %d.", hdr.request); > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > index 9a81ad912e..1ead5f653f 100644 > --- a/hw/virtio/virtio.c > +++ b/hw/virtio/virtio.c > @@ -14,6 +14,7 @@ > #include "qemu/osdep.h" > #include "qapi/error.h" > #include "qapi/qapi-commands-virtio.h" > +#include "hw/virtio/vhost-user-shmem.h" > #include "trace.h" > #include "qemu/defer-call.h" > #include "qemu/error-report.h" > @@ -3045,6 +3046,100 @@ int virtio_save(VirtIODevice *vdev, QEMUFile *f) > return vmstate_save_state(f, &vmstate_virtio, vdev, NULL); > } > =20 > +VirtioSharedMemory *virtio_new_shmem_region(VirtIODevice *vdev, uint8_t = shmid) > +{ > + VirtioSharedMemory *elem; > + g_autofree char *name =3D NULL; > + > + elem =3D g_new0(VirtioSharedMemory, 1); > + elem->shmid =3D shmid; > + > + /* Initialize embedded MemoryRegion as container for shmem mappings = */ > + name =3D g_strdup_printf("virtio-shmem-%d", shmid); > + memory_region_init(&elem->mr, OBJECT(vdev), name, UINT64_MAX); > + QTAILQ_INIT(&elem->mmaps); > + QSIMPLEQ_INSERT_TAIL(&vdev->shmem_list, elem, entry); > + return QSIMPLEQ_LAST(&vdev->shmem_list, VirtioSharedMemory, entry); "return elem;" is simpler. > +} > + > +VirtioSharedMemory *virtio_find_shmem_region(VirtIODevice *vdev, uint8_t= shmid) > +{ > + VirtioSharedMemory *shmem, *next; > + QSIMPLEQ_FOREACH_SAFE(shmem, &vdev->shmem_list, entry, next) { > + if (shmem->shmid =3D=3D shmid) { > + return shmem; > + } > + } > + return NULL; > +} > + > +int virtio_add_shmem_map(VirtioSharedMemory *shmem, > + VhostUserShmemObject *shmem_obj) > +{ > + VirtioSharedMemoryMapping *mmap; > + if (!shmem_obj) { > + error_report("VhostUserShmemObject cannot be NULL"); > + return -1; > + } > + if (!shmem_obj->mr) { > + error_report("VhostUserShmemObject has no MemoryRegion"); > + return -1; > + } > + > + /* Validate boundaries against the VIRTIO shared memory region */ > + if (shmem_obj->shm_offset + shmem_obj->len > shmem->mr.size) { =46rom above: memory_region_init(&elem->mr, OBJECT(vdev), name, UINT64_MAX); shmem->mr's size is UINT64_MAX and this if statement doesn't handle integer overflow. What is the purpose of this size check? > + error_report("Memory exceeds the shared memory boundaries"); > + return -1; > + } > + > + /* Create the VirtioSharedMemoryMapping wrapper */ > + mmap =3D g_new0(VirtioSharedMemoryMapping, 1); > + mmap->mem =3D shmem_obj->mr; > + mmap->offset =3D shmem_obj->shm_offset; > + mmap->shmem_obj =3D shmem_obj; > + > + /* Take a reference on the VhostUserShmemObject */ > + object_ref(OBJECT(shmem_obj)); Why is the reference count incremented here? The caller seems to pass ownership to this function...at least vhost_user_backend_handle_shmem_map() doesn't touch shmem_obj afterwards and doesn't unref it. > + > + /* Add as subregion to the VIRTIO shared memory */ > + memory_region_add_subregion(&shmem->mr, mmap->offset, mmap->mem); > + > + /* Add to the mapped regions list */ > + QTAILQ_INSERT_TAIL(&shmem->mmaps, mmap, link); > + > + return 0; > +} > + > +VirtioSharedMemoryMapping *virtio_find_shmem_map(VirtioSharedMemory *shm= em, > + hwaddr offset, uint64_t size) > +{ > + VirtioSharedMemoryMapping *mmap; > + QTAILQ_FOREACH(mmap, &shmem->mmaps, link) { > + if (mmap->offset =3D=3D offset && mmap->mem->size =3D=3D size) { > + return mmap; > + } > + } > + return NULL; > +} > + > +void virtio_del_shmem_map(VirtioSharedMemory *shmem, hwaddr offset, > + uint64_t size) > +{ > + VirtioSharedMemoryMapping *mmap =3D virtio_find_shmem_map(shmem, off= set, size); > + if (mmap =3D=3D NULL) { > + return; > + } > + > + /* > + * Unref the VhostUserShmemObject which will trigger automatic clean= up > + * when the reference count reaches zero. > + */ > + object_unref(OBJECT(mmap->shmem_obj)); > + > + QTAILQ_REMOVE(&shmem->mmaps, mmap, link); > + g_free(mmap); > +} > + > /* A wrapper for use as a VMState .put function */ > static int virtio_device_put(QEMUFile *f, void *opaque, size_t size, > const VMStateField *field, JSONWriter *vmd= esc) > @@ -3521,6 +3616,7 @@ void virtio_init(VirtIODevice *vdev, uint16_t devic= e_id, size_t config_size) > NULL, virtio_vmstate_change, vdev); > vdev->device_endian =3D virtio_default_endian(); > vdev->use_guest_notifier_mask =3D true; > + QSIMPLEQ_INIT(&vdev->shmem_list); > } > =20 > /* > @@ -4032,11 +4128,24 @@ static void virtio_device_free_virtqueues(VirtIOD= evice *vdev) > static void virtio_device_instance_finalize(Object *obj) > { > VirtIODevice *vdev =3D VIRTIO_DEVICE(obj); > + VirtioSharedMemory *shmem; > =20 > virtio_device_free_virtqueues(vdev); > =20 > g_free(vdev->config); > g_free(vdev->vector_queues); > + while (!QSIMPLEQ_EMPTY(&vdev->shmem_list)) { > + shmem =3D QSIMPLEQ_FIRST(&vdev->shmem_list); > + while (!QTAILQ_EMPTY(&shmem->mmaps)) { > + VirtioSharedMemoryMapping *mmap_reg =3D QTAILQ_FIRST(&shmem-= >mmaps); > + virtio_del_shmem_map(shmem, mmap_reg->offset, mmap_reg->mem-= >size); > + } > + > + /* Clean up the embedded MemoryRegion */ > + object_unparent(OBJECT(&shmem->mr)); > + QSIMPLEQ_REMOVE_HEAD(&vdev->shmem_list, entry); > + g_free(shmem); > + } > } > =20 > static const Property virtio_properties[] =3D { > diff --git a/include/hw/virtio/vhost-user-shmem.h b/include/hw/virtio/vho= st-user-shmem.h > new file mode 100644 > index 0000000000..1f8c7bdc1f > --- /dev/null > +++ b/include/hw/virtio/vhost-user-shmem.h > @@ -0,0 +1,75 @@ > +/* > + * VHost-user Shared Memory Object > + * > + * Copyright Red Hat, Inc. 2025 > + * > + * Authors: > + * Albert Esteve > + * > + * This work is licensed under the terms of the GNU GPL, version 2 or la= ter. > + * See the COPYING file in the top-level directory. > + */ > + > +#ifndef VHOST_USER_SHMEM_H > +#define VHOST_USER_SHMEM_H > + > +#include "qemu/osdep.h" > +#include "qom/object.h" > +#include "system/memory.h" > +#include "qapi/error.h" > + > +/* vhost-user memory mapping flags */ > +#define VHOST_USER_FLAG_MAP_RW (1u << 0) This constant is part of the vhost-user protocol. It would be nicer to keep that all in one file instead of spreading protocol definitions across multiple files. In this case you could replace vhost_user_shmem_object_new()'s flags argument with a bool allow_write argument. That way the vhost-user protocol parsing happens in vhost-user.c and not vhost-user-shmem.c. Alternatively, you could move the protocol definitions from vhost-user.c into a header file and include them from vhost-user-shmem.c. > + > +#define TYPE_VHOST_USER_SHMEM_OBJECT "vhost-user-shmem" > +OBJECT_DECLARE_SIMPLE_TYPE(VhostUserShmemObject, VHOST_USER_SHMEM_OBJECT) > + > +/** > + * VhostUserShmemObject: > + * @parent: Parent object > + * @shmid: VIRTIO Shared Memory Region ID > + * @fd: File descriptor for the shared memory region > + * @shm_offset: Offset within the VIRTIO Shared Memory Region > + * @len: Size of the mapping > + * @mr: MemoryRegion associated with this shared memory mapping > + * > + * An intermediate QOM object that manages individual shared memory mapp= ings > + * created by VHOST_USER_BACKEND_SHMEM_MAP requests. It acts as a parent= for > + * MemoryRegion objects, providing proper lifecycle management with refe= rence > + * counting. When the object is unreferenced and its reference count dro= ps > + * to zero, it automatically cleans up the MemoryRegion and unmaps the m= emory. > + */ > +struct VhostUserShmemObject { > + Object parent; > + > + uint8_t shmid; > + int fd; > + uint64_t shm_offset; > + uint64_t len; > + MemoryRegion *mr; > +}; > + > +/** > + * vhost_user_shmem_object_new() - Create a new VhostUserShmemObject > + * @shmid: VIRTIO Shared Memory Region ID > + * @fd: File descriptor for the shared memory > + * @fd_offset: Offset within the file descriptor > + * @shm_offset: Offset within the VIRTIO Shared Memory Region > + * @len: Size of the mapping > + * @flags: Mapping flags (VHOST_USER_FLAG_MAP_*) > + * > + * Creates a new VhostUserShmemObject that manages a shared memory mappi= ng. > + * The object will create a MemoryRegion using memory_region_init_ram_fr= om_fd() > + * as a child object. When the object is finalized, it will automatically > + * clean up the MemoryRegion and close the file descriptor. > + * > + * Return: A new VhostUserShmemObject on success, NULL on error. > + */ > +VhostUserShmemObject *vhost_user_shmem_object_new(uint8_t shmid, > + int fd, > + uint64_t fd_offset, > + uint64_t shm_offset, > + uint64_t len, > + uint16_t flags); > + > +#endif /* VHOST_USER_SHMEM_H */ > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h > index c594764f23..a563bbac2c 100644 > --- a/include/hw/virtio/virtio.h > +++ b/include/hw/virtio/virtio.h > @@ -98,6 +98,26 @@ enum virtio_device_endian { > VIRTIO_DEVICE_ENDIAN_BIG, > }; > =20 > +struct VhostUserShmemObject; > + > +struct VirtioSharedMemoryMapping { > + MemoryRegion *mem; > + hwaddr offset; > + QTAILQ_ENTRY(VirtioSharedMemoryMapping) link; > + struct VhostUserShmemObject *shmem_obj; /* Intermediate parent objec= t */ > +}; > + > +typedef struct VirtioSharedMemoryMapping VirtioSharedMemoryMapping; > + > +struct VirtioSharedMemory { > + uint8_t shmid; > + MemoryRegion mr; > + QTAILQ_HEAD(, VirtioSharedMemoryMapping) mmaps; > + QSIMPLEQ_ENTRY(VirtioSharedMemory) entry; > +}; VirtioSharedMemoryMapping and VirtioSharedMemory duplicate information =66rom VhostUserShmemObject (shmid, memory region pointers, offsets). This makes the relationship between VIRTIO and vhost-user code confusing. I wonder if VhostUserShmemObject is specific to the vhost-user protocol or if any VIRTIO device implementation that needs a VIRTIO Shared Memory Region with an fd, offset, etc should be able to use it? If yes, then it should be renamed and made part of the core hw/virtio/ code rather than vhost-user. > + > +typedef struct VirtioSharedMemory VirtioSharedMemory; > + > /** > * struct VirtIODevice - common VirtIO structure > * @name: name of the device > @@ -167,6 +187,8 @@ struct VirtIODevice > */ > EventNotifier config_notifier; > bool device_iotlb_enabled; > + /* Shared memory region for mappings. */ > + QSIMPLEQ_HEAD(, VirtioSharedMemory) shmem_list; > }; > =20 > struct VirtioDeviceClass { > @@ -295,6 +317,77 @@ void virtio_notify(VirtIODevice *vdev, VirtQueue *vq= ); > =20 > int virtio_save(VirtIODevice *vdev, QEMUFile *f); > =20 > +/** > + * virtio_new_shmem_region() - Create a new shared memory region > + * @vdev: VirtIODevice > + * @shmid: Shared memory ID > + * > + * Creates a new VirtioSharedMemory region for the given device and ID. > + * The returned VirtioSharedMemory is owned by the VirtIODevice and will > + * be automatically freed when the device is destroyed. The caller > + * should not free the returned pointer. > + * > + * Returns: Pointer to the new VirtioSharedMemory region, or NULL on fai= lure > + */ > +VirtioSharedMemory *virtio_new_shmem_region(VirtIODevice *vdev, uint8_t = shmid); > + > +/** > + * virtio_find_shmem_region() - Find an existing shared memory region > + * @vdev: VirtIODevice > + * @shmid: Shared memory ID to find > + * > + * Finds an existing VirtioSharedMemory region by ID. The returned point= er > + * is owned by the VirtIODevice and should not be freed by the caller. > + * > + * Returns: Pointer to the VirtioSharedMemory region, or NULL if not fou= nd > + */ > +VirtioSharedMemory *virtio_find_shmem_region(VirtIODevice *vdev, uint8_t= shmid); > + > +/** > + * virtio_add_shmem_map() - Add a memory mapping to a shared region > + * @shmem: VirtioSharedMemory region > + * @shmem_obj: VhostUserShmemObject to add (takes a reference) > + * > + * Adds a memory mapping to the shared memory region. The VhostUserShmem= Object > + * is added as a child of the mapping and will be automatically managed = through > + * QOM reference counting. The mapping will be removed when > + * virtio_del_shmem_map() is called or when the shared memory region is > + * destroyed. > + * > + * Returns: 0 on success, negative errno on failure > + */ > +int virtio_add_shmem_map(VirtioSharedMemory *shmem, > + struct VhostUserShmemObject *shmem_obj); This API suggests the answer to my question above about whether VhostUserShmemObject is really a core hw/virtio/ concept rather than a vhost-user protocol concept is "yes". I think VhostUserShmemObject should be renamed and maybe unified with VirtioSharedMemoryMapping. > + > +/** > + * virtio_find_shmem_map() - Find a memory mapping in a shared region > + * @shmem: VirtioSharedMemory region > + * @offset: Offset within the shared memory region > + * @size: Size of the mapping to find > + * > + * Finds an existing memory mapping that covers the specified range. > + * The returned VirtioSharedMemoryMapping is owned by the VirtioSharedMe= mory > + * region and should not be freed by the caller. > + * > + * Returns: Pointer to the VirtioSharedMemoryMapping, or NULL if not fou= nd > + */ > +VirtioSharedMemoryMapping *virtio_find_shmem_map(VirtioSharedMemory *shm= em, > + hwaddr offset, uint64_t size); > + > +/** > + * virtio_del_shmem_map() - Remove a memory mapping from a shared region > + * @shmem: VirtioSharedMemory region > + * @offset: Offset of the mapping to remove > + * @size: Size of the mapping to remove > + * > + * Removes a memory mapping from the shared memory region. This will > + * automatically unref the associated VhostUserShmemObject, which may > + * trigger its finalization and cleanup if no other references exist. > + * The mapping's MemoryRegion will be properly unmapped and cleaned up. > + */ > +void virtio_del_shmem_map(VirtioSharedMemory *shmem, hwaddr offset, > + uint64_t size); > + > extern const VMStateInfo virtio_vmstate_info; > =20 > #define VMSTATE_VIRTIO_DEVICE \ > diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libv= host-user/libvhost-user.c > index 9c630c2170..034cbfdc3c 100644 > --- a/subprojects/libvhost-user/libvhost-user.c > +++ b/subprojects/libvhost-user/libvhost-user.c > @@ -1592,6 +1592,76 @@ vu_rm_shared_object(VuDev *dev, unsigned char uuid= [UUID_LEN]) > return vu_send_message(dev, &msg); > } > =20 > +bool > +vu_shmem_map(VuDev *dev, uint8_t shmid, uint64_t fd_offset, > + uint64_t shm_offset, uint64_t len, uint64_t flags, int fd) > +{ > + VhostUserMsg vmsg =3D { > + .request =3D VHOST_USER_BACKEND_SHMEM_MAP, > + .size =3D sizeof(vmsg.payload.mmap), > + .flags =3D VHOST_USER_VERSION, > + .payload.mmap =3D { > + .shmid =3D shmid, > + .fd_offset =3D fd_offset, > + .shm_offset =3D shm_offset, > + .len =3D len, > + .flags =3D flags, > + }, > + .fd_num =3D 1, > + .fds[0] =3D fd, > + }; > + > + if (!vu_has_protocol_feature(dev, VHOST_USER_PROTOCOL_F_SHMEM)) { > + return false; > + } > + > + if (vu_has_protocol_feature(dev, VHOST_USER_PROTOCOL_F_REPLY_ACK)) { > + vmsg.flags |=3D VHOST_USER_NEED_REPLY_MASK; > + } > + > + pthread_mutex_lock(&dev->backend_mutex); > + if (!vu_message_write(dev, dev->backend_fd, &vmsg)) { > + pthread_mutex_unlock(&dev->backend_mutex); > + return false; > + } > + > + /* Also unlocks the backend_mutex */ > + return vu_process_message_reply(dev, &vmsg); > +} > + > +bool > +vu_shmem_unmap(VuDev *dev, uint8_t shmid, uint64_t shm_offset, uint64_t = len) > +{ > + VhostUserMsg vmsg =3D { > + .request =3D VHOST_USER_BACKEND_SHMEM_UNMAP, > + .size =3D sizeof(vmsg.payload.mmap), > + .flags =3D VHOST_USER_VERSION, > + .payload.mmap =3D { > + .shmid =3D shmid, > + .fd_offset =3D 0, > + .shm_offset =3D shm_offset, > + .len =3D len, > + }, > + }; > + > + if (!vu_has_protocol_feature(dev, VHOST_USER_PROTOCOL_F_SHMEM)) { > + return false; > + } > + > + if (vu_has_protocol_feature(dev, VHOST_USER_PROTOCOL_F_REPLY_ACK)) { > + vmsg.flags |=3D VHOST_USER_NEED_REPLY_MASK; > + } > + > + pthread_mutex_lock(&dev->backend_mutex); > + if (!vu_message_write(dev, dev->backend_fd, &vmsg)) { > + pthread_mutex_unlock(&dev->backend_mutex); > + return false; > + } > + > + /* Also unlocks the backend_mutex */ > + return vu_process_message_reply(dev, &vmsg); > +} > + > static bool > vu_set_vring_call_exec(VuDev *dev, VhostUserMsg *vmsg) > { > diff --git a/subprojects/libvhost-user/libvhost-user.h b/subprojects/libv= host-user/libvhost-user.h > index 2ffc58c11b..26b710c92d 100644 > --- a/subprojects/libvhost-user/libvhost-user.h > +++ b/subprojects/libvhost-user/libvhost-user.h > @@ -69,6 +69,8 @@ enum VhostUserProtocolFeature { > /* Feature 16 is reserved for VHOST_USER_PROTOCOL_F_STATUS. */ > /* Feature 17 reserved for VHOST_USER_PROTOCOL_F_XEN_MMAP. */ > VHOST_USER_PROTOCOL_F_SHARED_OBJECT =3D 18, > + /* Feature 19 is reserved for VHOST_USER_PROTOCOL_F_DEVICE_STATE */ > + VHOST_USER_PROTOCOL_F_SHMEM =3D 20, > VHOST_USER_PROTOCOL_F_MAX > }; > =20 > @@ -127,6 +129,8 @@ typedef enum VhostUserBackendRequest { > VHOST_USER_BACKEND_SHARED_OBJECT_ADD =3D 6, > VHOST_USER_BACKEND_SHARED_OBJECT_REMOVE =3D 7, > VHOST_USER_BACKEND_SHARED_OBJECT_LOOKUP =3D 8, > + VHOST_USER_BACKEND_SHMEM_MAP =3D 9, > + VHOST_USER_BACKEND_SHMEM_UNMAP =3D 10, > VHOST_USER_BACKEND_MAX > } VhostUserBackendRequest; > =20 > @@ -186,6 +190,23 @@ typedef struct VhostUserShared { > unsigned char uuid[UUID_LEN]; > } VhostUserShared; > =20 > +/* For the flags field of VhostUserMMap */ > +#define VHOST_USER_FLAG_MAP_RW (1u << 0) > + > +typedef struct { > + /* VIRTIO Shared Memory Region ID */ > + uint8_t shmid; > + uint8_t padding[7]; > + /* File offset */ > + uint64_t fd_offset; > + /* Offset within the VIRTIO Shared Memory Region */ > + uint64_t shm_offset; > + /* Size of the mapping */ > + uint64_t len; > + /* Flags for the mmap operation, from VHOST_USER_FLAG_MAP_* */ > + uint16_t flags; > +} VhostUserMMap; > + > #define VU_PACKED __attribute__((packed)) > =20 > typedef struct VhostUserMsg { > @@ -210,6 +231,7 @@ typedef struct VhostUserMsg { > VhostUserVringArea area; > VhostUserInflight inflight; > VhostUserShared object; > + VhostUserMMap mmap; > } payload; > =20 > int fds[VHOST_MEMORY_BASELINE_NREGIONS]; > @@ -593,6 +615,38 @@ bool vu_add_shared_object(VuDev *dev, unsigned char = uuid[UUID_LEN]); > */ > bool vu_rm_shared_object(VuDev *dev, unsigned char uuid[UUID_LEN]); > =20 > +/** > + * vu_shmem_map: > + * @dev: a VuDev context > + * @shmid: VIRTIO Shared Memory Region ID > + * @fd_offset: File offset > + * @shm_offset: Offset within the VIRTIO Shared Memory Region > + * @len: Size of the mapping > + * @flags: Flags for the mmap operation > + * @fd: A file descriptor > + * > + * Advertises a new mapping to be made in a given VIRTIO Shared Memory R= egion. > + * > + * Returns: TRUE on success, FALSE on failure. > + */ > +bool vu_shmem_map(VuDev *dev, uint8_t shmid, uint64_t fd_offset, > + uint64_t shm_offset, uint64_t len, uint64_t flags, int= fd); > + > +/** > + * vu_shmem_unmap: > + * @dev: a VuDev context > + * @shmid: VIRTIO Shared Memory Region ID > + * @fd_offset: File offset > + * @len: Size of the mapping > + * > + * The front-end un-mmaps a given range in the VIRTIO Shared Memory Regi= on > + * with the requested `shmid`. > + * > + * Returns: TRUE on success, FALSE on failure. > + */ > +bool vu_shmem_unmap(VuDev *dev, uint8_t shmid, uint64_t shm_offset, > + uint64_t len); > + > /** > * vu_queue_set_notification: > * @dev: a VuDev context > --=20 > 2.49.0 >=20 --ZwZCyUvPYykV+HTW Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmijd8cACgkQnKSrs4Gr c8ginQf/YaWN4Y2JICt3vi8nTXkyCXQ/6+Yqb7+HxtA2CqjEm/ula39DrqSceDCh 2VZIvCw5Wm+6N59lzF2amWetoSU3ytOTZugO5XcB9HnPXtJBNKjIqs7frtzXN/5a 2W3mlurxEQ42ebQ7jaJovbq5jWOV1lJlnn1GTPUeUvIzdwOV+76ekKkAhIINDail sPt6hec4h0pJLFjNw0fUTpSfc300kjeWE22eobnURc3Wf2xJx21iN3uSJoNEbEpK dLMC9oawN/zR5f5/1LYIyQKzvGT0+dwu3s0RoEmc5LcPMfFrsKqsOKKIZuuyb0fJ HfiuYkp13+iimNbmkCQOy5ILJOob2g== =eHWS -----END PGP SIGNATURE----- --ZwZCyUvPYykV+HTW--