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  • Stefano Garzarella's avatar
    hostmem: add a new memory backend based on POSIX shm_open() · 4e647fa0
    Stefano Garzarella authored and MST's avatar MST committed
    shm_open() creates and opens a new POSIX shared memory object.
    A POSIX shared memory object allows creating memory backend with an
    associated file descriptor that can be shared with external processes
    (e.g. vhost-user).
    The new `memory-backend-shm` can be used as an alternative when
    `memory-backend-memfd` is not available (Linux only), since shm_open()
    should be provided by any POSIX-compliant operating system.
    This backend mimics memfd, allocating memory that is practically
    anonymous. In theory shm_open() requires a name, but this is allocated
    for a short time interval and shm_unlink() is called right after
    shm_open(). After that, only fd is shared with external processes
    (e.g., vhost-user) as if it were associated with anonymous memory.
    In the future we may also allow the user to specify the name to be
    passed to shm_open(), but for now we keep the backend simple, mimicking
    anonymous memory such as memfd.
    Acked-by: David Hildenbrand's avatarDavid Hildenbrand <>
    Acked-by: Stefan Hajnoczi's avatarStefan Hajnoczi <>
    Acked-by: Markus Armbruster <> (QAPI schema)
    Signed-off-by: Stefano Garzarella's avatarStefano Garzarella <>
    Message-Id: <>
    Reviewed-by: MST's avatarMichael S. Tsirkin <>
    Signed-off-by: MST's avatarMichael S. Tsirkin <>