vhost_user: Add frontend get_shmem_config command
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. This is useful when the frontend is unaware of specific backend type and configuration, for example, in the `vhost-user-device` case. Reviewed-by: Stefano Garzarella <sgarzare@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Albert Esteve <aesteve@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Message-Id: <20260304165223.2166175-5-aesteve@redhat.com>
Albert Esteve committed
Mar 4, 2026 at 17:52 UTC
458f80f661e51d09936efb53eaba7c0d81ba323c
4 files changed
+16
-1
include/hw/virtio/vhost-backend.h
+10
@@ -162,6 +162,15 @@ typedef int (*vhost_set_device_state_fd_op)(struct vhost_dev *dev,
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int *reply_fd,
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Error **errp);
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typedef int (*vhost_check_device_state_op)(struct vhost_dev *dev, Error **errp);
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+/*
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+ * Max regions is VIRTIO_MAX_SHMEM_REGIONS, so that is the maximum
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+ * number of memory_sizes that will be accepted.
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+ */
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+typedef int (*vhost_get_shmem_config_op)(struct vhost_dev *dev,
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+ int *nregions,
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+ uint64_t *memory_sizes,
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+ Error **errp);
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+
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typedef struct VhostOps {
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VhostBackendType backend_type;
@@ -220,6 +229,7 @@ typedef struct VhostOps {
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vhost_supports_device_state_op vhost_supports_device_state;
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vhost_set_device_state_fd_op vhost_set_device_state_fd;
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vhost_check_device_state_op vhost_check_device_state;
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+ vhost_get_shmem_config_op vhost_get_shmem_config;
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} VhostOps;
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int vhost_user_gpu_set_socket(struct vhost_dev *dev, int fd);
include/hw/virtio/vhost-user.h
+1
@@ -35,6 +35,7 @@ enum VhostUserProtocolFeature {
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VHOST_USER_PROTOCOL_F_DEVICE_STATE = 19,
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VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT = 20,
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VHOST_USER_PROTOCOL_F_GPA_ADDRESSES = 21,
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+ VHOST_USER_PROTOCOL_F_SHMEM = 22,
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VHOST_USER_PROTOCOL_F_MAX
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};
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include/hw/virtio/virtio.h
+2
@@ -82,6 +82,8 @@ typedef struct VirtQueueElement
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#define VIRTIO_NO_VECTOR 0xffff
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+#define VIRTIO_MAX_SHMEM_REGIONS 256
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+
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/* special index value used internally for config irqs */
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#define VIRTIO_CONFIG_IRQ_IDX -1
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subprojects/libvhost-user/libvhost-user.h
+3
-1
@@ -70,7 +70,9 @@ enum VhostUserProtocolFeature {
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/* Feature 17 reserved for VHOST_USER_PROTOCOL_F_XEN_MMAP. */
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VHOST_USER_PROTOCOL_F_SHARED_OBJECT = 18,
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/* Feature 19 is reserved for VHOST_USER_PROTOCOL_F_DEVICE_STATE */
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- VHOST_USER_PROTOCOL_F_SHMEM = 20,
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+ /* Feature 20 is reserved for VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT */
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+ /* Feature 21 is reserved for VHOST_USER_PROTOCOL_F_GPA_ADDRESSES */
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+ VHOST_USER_PROTOCOL_F_SHMEM = 22,
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VHOST_USER_PROTOCOL_F_MAX
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};
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