// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
library fuchsia.virtualization;

using zx;

/// Contains a memory statistic for the balloon device.
type MemStat = struct {
    tag uint16;
    val uint64;
};

/// A `BalloonController` controls a guest instance's memory balloon.
@discoverable
protocol BalloonController {
    /// Get the number of pages in the memory balloon.
    GetNumPages() -> (struct {
        num_pages uint32;
    });

    /// Request a number of pages to be supplied to the memory balloon.
    ///
    /// If `num_pages` is greater than the current value, the guest instance will
    /// provide additional pages to the memory balloon. If `num_pages` is less
    /// than the current value, the guest instance is free to reclaim pages from
    /// the memory balloon.
    RequestNumPages(struct {
        num_pages uint32;
    });

    /// Get memory statistics of the guest instance.
    GetMemStats() -> (struct {
        status zx.status;
        mem_stats vector<MemStat>:optional;
    });
};