Method remove_user_memory_region

hypervisor/src/kvm/mod.rs:1122–1167

Removes a guest physical memory region. # Safety `userspace_addr` must point to `memory_size` bytes of memory, and `add_user_memory_region()` must have been successfully called.

(
        &self,
        slot: u32,
        guest_phys_addr: u64,
        memory_size: usize,
        userspace_addr: *mut u8,
        readonly: bool,
        log_dirty_pages: bool,
    )

    /// `userspace_addr` must point to `memory_size` bytes of memory,
    /// and `add_user_memory_region()` must have been successfully called.
    unsafe fn remove_user_memory_region(
        &self,
        slot: u32,
        guest_phys_addr: u64,
        memory_size: usize,
        userspace_addr: *mut u8,
        readonly: bool,
        log_dirty_pages: bool,
    ) -> vm::Result<()> {
        let mut flags = 0;
        if readonly {
            flags |= KVM_MEM_READONLY;
        }
        if log_dirty_pages {
            flags |= KVM_MEM_LOG_DIRTY_PAGES;
        }

        const _: () = assert!(core::mem::size_of::<usize>() <= core::mem::size_of::<u64>());

        let mut region = kvm_userspace_memory_region2 {
            slot,
            guest_phys_addr,
            memory_size: memory_size as u64,
            userspace_addr: userspace_addr as usize as u64,
            flags,
            ..Default::default()
        };

        // Remove the corresponding entry from "self.dirty_log_slots" if needed
        self.dirty_log_slots.write().unwrap().remove(&region.slot);

        // Setting the size to 0 means "remove"
        region.memory_size = 0;
        // SAFETY: Safe because caller promised this is safe.
        unsafe {
            self.set_user_memory_region(region)
                .map_err(|e| vm::HypervisorVmError::RemoveUserMemory(e.into()))?;
        }

        // Close the per-region guest_memfd if one was created for this slot
        if let Some(slots) = &self.memory_slots {
            slots.write().unwrap().remove(&slot);
        }

        Ok(())
    }

    ///
    /// Returns the preferred CPU target type which can be emulated by KVM on underlying host.