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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1771506273; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YgMuFHE4xgIPRrBqWIR+Qt/vy3i50/JPFOfHKHeqU+s=; b=JEC8NZCRia3p9IIdbz7MdeQe1SHCHxPpK0ArR9YkNIe4msJM5E04K5ygtLdRHFSLDwC/yC 2Fj7IlJ2qcco9Ld6HN2nu7OjkuJ5yPTHx/o5Bvwjo+hgkJbixXiaN1lQfDuOoFm9E+jkO6 Ao2DnsuOnGOCGgWxBpQWliG5Zq8VNeY= X-MC-Unique: r1sxKKX1PCS3tECIIoSdhg-1 X-Mimecast-MFC-AGG-ID: r1sxKKX1PCS3tECIIoSdhg_1771506269 From: Albert Esteve To: qemu-devel@nongnu.org Cc: Peter Xu , Pierrick Bouvier , mst@redhat.com, dbassey@redhat.com, =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , =?UTF-8?q?Alex=20Benn=C3=A9e?= , Paolo Bonzini , Fabiano Rosas , stefanha@redhat.com, manos.pitsidianakis@linaro.org, Stefano Garzarella , jasowang@redhat.com, Laurent Vivier , slp@redhat.com, hi@alyssa.is, stevensd@chromium.org Subject: [PATCH v13 7/7] vhost-user-device: Add shared memory BAR Date: Thu, 19 Feb 2026 14:03:34 +0100 Message-ID: <20260219130334.787858-8-aesteve@redhat.com> In-Reply-To: <20260219130334.787858-1-aesteve@redhat.com> References: <20260219130334.787858-1-aesteve@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; 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charset="utf-8" Add shared memory BAR support to vhost-user-device-pci to enable direct file mapping for VIRTIO Shared Memory Regions. The implementation creates a consolidated shared memory BAR that contains all VIRTIO Shared Memory Regions as subregions. Each region is configured with its proper shmid, size, and offset within the BAR. The number and size of regions are retrieved via VHOST_USER_GET_SHMEM_CONFIG message sent by vhost-user-base during realization after virtio_init(). Specifiically, it uses BAR 3 to avoid conflicts, as it is currently unused. The shared memory BAR is only created when the backend supports VHOST_USER_PROTOCOL_F_SHMEM and has configured shared memory regions. This maintains backward compatibility with backends that do not support shared memory functionality. Reviewed-by: Stefan Hajnoczi Signed-off-by: Albert Esteve Reviewed-by: Stefano Garzarella --- hw/virtio/vhost-user-base.c | 46 ++++++++++++++++++++++++-- hw/virtio/vhost-user-test-device-pci.c | 38 +++++++++++++++++++-- 2 files changed, 79 insertions(+), 5 deletions(-) diff --git a/hw/virtio/vhost-user-base.c b/hw/virtio/vhost-user-base.c index 01ab9ca56b..e5e8abae96 100644 --- a/hw/virtio/vhost-user-base.c +++ b/hw/virtio/vhost-user-base.c @@ -16,6 +16,7 @@ #include "hw/virtio/virtio-bus.h" #include "hw/virtio/vhost-user-base.h" #include "qemu/error-report.h" +#include "migration/blocker.h" =20 static void vub_start(VirtIODevice *vdev) { @@ -276,7 +277,8 @@ static void vub_device_realize(DeviceState *dev, Error = **errp) { VirtIODevice *vdev =3D VIRTIO_DEVICE(dev); VHostUserBase *vub =3D VHOST_USER_BASE(dev); - int ret; + uint64_t memory_sizes[VIRTIO_MAX_SHMEM_REGIONS]; + int i, ret, nregions, regions_processed =3D 0; =20 if (!vub->chardev.chr) { error_setg(errp, "vhost-user-base: missing chardev"); @@ -319,7 +321,7 @@ static void vub_device_realize(DeviceState *dev, Error = **errp) =20 /* Allocate queues */ vub->vqs =3D g_ptr_array_sized_new(vub->num_vqs); - for (int i =3D 0; i < vub->num_vqs; i++) { + for (i =3D 0; i < vub->num_vqs; i++) { g_ptr_array_add(vub->vqs, virtio_add_queue(vdev, vub->vq_size, vub_handle_output)); @@ -333,11 +335,49 @@ static void vub_device_realize(DeviceState *dev, Erro= r **errp) VHOST_BACKEND_TYPE_USER, 0, errp); =20 if (ret < 0) { - do_vhost_user_cleanup(vdev, vub); + goto err; + } + + ret =3D vub->vhost_dev.vhost_ops->vhost_get_shmem_config(&vub->vhost_d= ev, + &nregions, + memory_sizes, + errp); + + if (ret < 0) { + goto err; + } + + for (i =3D 0; i < VIRTIO_MAX_SHMEM_REGIONS && regions_processed < nreg= ions; i++) { + if (memory_sizes[i]) { + regions_processed++; + if (vub->vhost_dev.migration_blocker =3D=3D NULL) { + error_setg(&vub->vhost_dev.migration_blocker, + "Migration disabled: devices with VIRTIO Shared Mem= ory " + "Regions do not support migration yet."); + ret =3D migrate_add_blocker_normal( + &vub->vhost_dev.migration_blocker, + errp); + + if (ret < 0) { + goto err; + } + } + + if (memory_sizes[i] % qemu_real_host_page_size() !=3D 0) { + error_setg(errp, "Shared memory %d size must be a power of= 2 " + "no smaller than the page size", i); + goto err; + } + + virtio_new_shmem_region(vdev, i, memory_sizes[i]); + } } =20 qemu_chr_fe_set_handlers(&vub->chardev, NULL, NULL, vub_event, NULL, dev, NULL, true); + return; +err: + do_vhost_user_cleanup(vdev, vub); } =20 static void vub_device_unrealize(DeviceState *dev) diff --git a/hw/virtio/vhost-user-test-device-pci.c b/hw/virtio/vhost-user-= test-device-pci.c index 7f6d751690..22678e3277 100644 --- a/hw/virtio/vhost-user-test-device-pci.c +++ b/hw/virtio/vhost-user-test-device-pci.c @@ -12,10 +12,13 @@ #include "hw/virtio/vhost-user-base.h" #include "hw/virtio/virtio-pci.h" =20 +#define VIRTIO_DEVICE_PCI_SHMEM_BAR 4 + struct VHostUserDevicePCI { VirtIOPCIProxy parent_obj; =20 VHostUserBase vub; + MemoryRegion shmembar; }; =20 #define TYPE_VHOST_USER_TEST_DEVICE_PCI "vhost-user-test-device-pci-base" @@ -25,10 +28,41 @@ OBJECT_DECLARE_SIMPLE_TYPE(VHostUserDevicePCI, VHOST_US= ER_TEST_DEVICE_PCI) static void vhost_user_device_pci_realize(VirtIOPCIProxy *vpci_dev, Error = **errp) { VHostUserDevicePCI *dev =3D VHOST_USER_TEST_DEVICE_PCI(vpci_dev); - DeviceState *vdev =3D DEVICE(&dev->vub); + DeviceState *dev_state =3D DEVICE(&dev->vub); + VirtIODevice *vdev =3D VIRTIO_DEVICE(dev_state); + VirtioSharedMemory *shmem, *next; + uint64_t offset =3D 0, shmem_size =3D 0; =20 + vpci_dev->modern_mem_bar_idx =3D 2; vpci_dev->nvectors =3D 1; - qdev_realize(vdev, BUS(&vpci_dev->bus), errp); + qdev_realize(dev_state, BUS(&vpci_dev->bus), errp); + + QSIMPLEQ_FOREACH_SAFE(shmem, &vdev->shmem_list, entry, next) { + if (shmem->mr.size > UINT64_MAX - shmem_size) { + error_setg(errp, "Total shared memory required overflow"); + return; + } + shmem_size =3D shmem_size + shmem->mr.size; + } + if (shmem_size) { + if (vpci_dev->flags & VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY) { + error_setg(errp, "modern-pio-notify is not supported due to PC= I BAR layout limitations"); + return; + } + memory_region_init(&dev->shmembar, OBJECT(vpci_dev), + "vhost-device-pci-shmembar", shmem_size); + QSIMPLEQ_FOREACH_SAFE(shmem, &vdev->shmem_list, entry, next) { + memory_region_add_subregion(&dev->shmembar, offset, &shmem->mr= ); + virtio_pci_add_shm_cap(vpci_dev, VIRTIO_DEVICE_PCI_SHMEM_BAR, + offset, shmem->mr.size, shmem->shmid); + offset =3D offset + shmem->mr.size; + } + pci_register_bar(&vpci_dev->pci_dev, VIRTIO_DEVICE_PCI_SHMEM_BAR, + PCI_BASE_ADDRESS_SPACE_MEMORY | + PCI_BASE_ADDRESS_MEM_PREFETCH | + PCI_BASE_ADDRESS_MEM_TYPE_64, + &dev->shmembar); + } } =20 static void vhost_user_device_pci_class_init(ObjectClass *klass, --=20 2.52.0