hw/virtio-balloon.c

/*
 * Virtio Block Device
 *
 * Copyright IBM, Corp. 2008
 *
 * Authors:
 *  Anthony Liguori   <aliguori@us.ibm.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2.  See
 * the COPYING file in the top-level directory.
 *
 */

#include "qemu-common.h"
#include "virtio.h"
#include "pc.h"
#include "sysemu.h"
#include "cpu.h"
#include "balloon.h"
#include "virtio-balloon.h"
#include "kvm.h"

#if defined(__linux__)
#include <sys/mman.h>
#endif

typedef struct VirtIOBalloon
{
    VirtIODevice vdev;
    VirtQueue *ivq, *dvq;
    uint32_t num_pages;
    uint32_t actual;
} VirtIOBalloon;

static VirtIOBalloon *to_virtio_balloon(VirtIODevice *vdev)
{
    return (VirtIOBalloon *)vdev;
}

static void balloon_page(void *addr, int deflate)
{
#if defined(__linux__)
    if (!kvm_enabled() || kvm_has_sync_mmu())
        madvise(addr, TARGET_PAGE_SIZE,
                deflate ? MADV_WILLNEED : MADV_DONTNEED);
#endif
}

/* FIXME: once we do a virtio refactoring, this will get subsumed into common
 * code */
static size_t memcpy_from_iovector(void *data, size_t offset, size_t size,
                                   struct iovec *iov, int iovlen)
{
    int i;
    uint8_t *ptr = data;
    size_t iov_off = 0;
    size_t data_off = 0;

    for (i = 0; i < iovlen && size; i++) {
        if (offset < (iov_off + iov[i].iov_len)) {
            size_t len = MIN((iov_off + iov[i].iov_len) - offset , size);

            memcpy(ptr + data_off, iov[i].iov_base + (offset - iov_off), len);

            data_off += len;
            offset += len;
            size -= len;
        }

        iov_off += iov[i].iov_len;
    }

    return data_off;
}

static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
{
    VirtIOBalloon *s = to_virtio_balloon(vdev);
    VirtQueueElement elem;

    while (virtqueue_pop(vq, &elem)) {
        size_t offset = 0;
        uint32_t pfn;

        while (memcpy_from_iovector(&pfn, offset, 4,
                                    elem.out_sg, elem.out_num) == 4) {
            ram_addr_t pa;
            ram_addr_t addr;

            pa = (ram_addr_t)ldl_p(&pfn) << VIRTIO_BALLOON_PFN_SHIFT;
            offset += 4;

            addr = cpu_get_physical_page_desc(pa);
            if ((addr & ~TARGET_PAGE_MASK) != IO_MEM_RAM)
                continue;

            /* Using qemu_get_ram_ptr is bending the rules a bit, but
               should be OK because we only want a single page.  */
            balloon_page(qemu_get_ram_ptr(addr), !!(vq == s->dvq));
        }

        virtqueue_push(vq, &elem, offset);
        virtio_notify(vdev, vq);
    }
}

static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t *config_data)
{
    VirtIOBalloon *dev = to_virtio_balloon(vdev);
    struct virtio_balloon_config config;

    config.num_pages = cpu_to_le32(dev->num_pages);
    config.actual = cpu_to_le32(dev->actual);

    memcpy(config_data, &config, 8);
}

static void virtio_balloon_set_config(VirtIODevice *vdev,
                                      const uint8_t *config_data)
{
    VirtIOBalloon *dev = to_virtio_balloon(vdev);
    struct virtio_balloon_config config;
    memcpy(&config, config_data, 8);
    dev->actual = config.actual;
}

static uint32_t virtio_balloon_get_features(VirtIODevice *vdev)
{
    return 0;
}

static ram_addr_t virtio_balloon_to_target(void *opaque, ram_addr_t target)
{
    VirtIOBalloon *dev = opaque;

    if (target > ram_size)
        target = ram_size;

    if (target) {
        dev->num_pages = (ram_size - target) >> VIRTIO_BALLOON_PFN_SHIFT;
        virtio_notify_config(&dev->vdev);
    }

    return ram_size - (dev->actual << VIRTIO_BALLOON_PFN_SHIFT);
}

static void virtio_balloon_save(QEMUFile *f, void *opaque)
{
    VirtIOBalloon *s = opaque;

    virtio_save(&s->vdev, f);

    qemu_put_be32(f, s->num_pages);
    qemu_put_be32(f, s->actual);
}

static int virtio_balloon_load(QEMUFile *f, void *opaque, int version_id)
{
    VirtIOBalloon *s = opaque;

    if (version_id != 1)
        return -EINVAL;

    virtio_load(&s->vdev, f);

    s->num_pages = qemu_get_be32(f);
    s->actual = qemu_get_be32(f);

    return 0;
}

VirtIODevice *virtio_balloon_init(DeviceState *dev)
{
    VirtIOBalloon *s;

    s = (VirtIOBalloon *)virtio_common_init("virtio-balloon",
                                            VIRTIO_ID_BALLOON,
                                            8, sizeof(VirtIOBalloon));

    s->vdev.get_config = virtio_balloon_get_config;
    s->vdev.set_config = virtio_balloon_set_config;
    s->vdev.get_features = virtio_balloon_get_features;

    s->ivq = virtio_add_queue(&s->vdev, 128, virtio_balloon_handle_output);
    s->dvq = virtio_add_queue(&s->vdev, 128, virtio_balloon_handle_output);

    qemu_add_balloon_handler(virtio_balloon_to_target, s);

    register_savevm("virtio-balloon", -1, 1, virtio_balloon_save, virtio_balloon_load, s);

    return &s->vdev;
}