Method create_userspace_mapping

vmm/src/memory_manager.rs:2288–2363

# Safety `userspace_addr` and `memory_size` must be and remain valid until `remove_userspace_mapping` is called.

(
        &mut self,
        guest_phys_addr: u64,
        memory_size: usize,
        userspace_addr: *mut u8,
        mergeable: bool,
        readonly: bool,
        log_dirty: bool,
    )

    /// `userspace_addr` and `memory_size` must be and remain valid
    /// until `remove_userspace_mapping` is called.
    pub unsafe fn create_userspace_mapping(
        &mut self,
        guest_phys_addr: u64,
        memory_size: usize,
        userspace_addr: *mut u8,
        mergeable: bool,
        readonly: bool,
        log_dirty: bool,
    ) -> Result<u32, Error> {
        let slot = self.allocate_memory_slot();

        info!(
            "Creating userspace mapping: {guest_phys_addr:x} -> {userspace_addr_:x} {memory_size:x}, slot {slot}",
            userspace_addr_ = userspace_addr as u64
        );

        // SAFETY: caller promises parameters are correct.
        unsafe {
            self.vm
                .create_user_memory_region(
                    slot,
                    guest_phys_addr,
                    memory_size,
                    userspace_addr,
                    readonly,
                    log_dirty,
                )
                .map_err(Error::CreateUserMemoryRegion)?;
        }

        // SAFETY: the address and size are valid since the
        // mmap succeeded.
        let ret = unsafe {
            libc::madvise(
                userspace_addr.cast(),
                memory_size as libc::size_t,
                libc::MADV_DONTDUMP,
            )
        };
        if ret != 0 {
            let e = io::Error::last_os_error();
            warn!("Failed to mark mapping as MADV_DONTDUMP: {e}");
        }

        // Mark the pages as mergeable if explicitly asked for.
        if mergeable {
            // SAFETY: the address and size are valid since the
            // mmap succeeded.
            let ret = unsafe {
                libc::madvise(
                    userspace_addr.cast(),
                    memory_size as libc::size_t,
                    libc::MADV_MERGEABLE,
                )
            };
            if ret != 0 {
                let err = io::Error::last_os_error();
                // Safe to unwrap because the error is constructed with