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virtio-rng: use virtqueue_get_avail_bytes, fix migration

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Popping an elem from the vq just to find out its length causes problems
with save/load later on.  Use the new virtqueue_get_avail_bytes()
function instead, saves us the complexity in the migration code, as well
as makes the migration endian-safe.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Reviewed-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Amit Shah 2012-11-21 11:21:18 +05:30 committed by Anthony Liguori
parent 25d87288b1
commit 1441703965
1 changed files with 12 additions and 64 deletions
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76
hw/virtio-rng.c
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@ -22,14 +22,10 @@ typedef struct VirtIORNG {
/* Only one vq - guest puts buffer(s) on it when it needs entropy */
VirtQueue *vq;
VirtQueueElement elem;
/* Config data for the device -- currently only chardev */
VirtIORNGConf *conf;
/* Whether we've popped a vq element into 'elem' above */
bool popped;
RngBackend *rng;
/* We purposefully don't migrate this state. The quota will reset on the
@ -48,17 +44,12 @@ static bool is_guest_ready(VirtIORNG *vrng)
return false;
}
static size_t pop_an_elem(VirtIORNG *vrng)
static size_t get_request_size(VirtQueue *vq)
{
size_t size;
unsigned int in, out;
if (!vrng->popped && !virtqueue_pop(vrng->vq, &vrng->elem)) {
return 0;
}
vrng->popped = true;
size = iov_size(vrng->elem.in_sg, vrng->elem.in_num);
return size;
virtqueue_get_avail_bytes(vq, &in, &out);
return in;
}
static void virtio_rng_process(VirtIORNG *vrng);
@ -67,6 +58,7 @@ static void virtio_rng_process(VirtIORNG *vrng);
static void chr_read(void *opaque, const void *buf, size_t size)
{
VirtIORNG *vrng = opaque;
VirtQueueElement elem;
size_t len;
int offset;
@ -78,15 +70,14 @@ static void chr_read(void *opaque, const void *buf, size_t size)
offset = 0;
while (offset < size) {
if (!pop_an_elem(vrng)) {
if (!virtqueue_pop(vrng->vq, &elem)) {
break;
}
len = iov_from_buf(vrng->elem.in_sg, vrng->elem.in_num,
len = iov_from_buf(elem.in_sg, elem.in_num,
0, buf + offset, size - offset);
offset += len;
virtqueue_push(vrng->vq, &vrng->elem, len);
vrng->popped = false;
virtqueue_push(vrng->vq, &elem, len);
}
virtio_notify(&vrng->vdev, vrng->vq);
@ -100,21 +91,19 @@ static void chr_read(void *opaque, const void *buf, size_t size)
static void virtio_rng_process(VirtIORNG *vrng)
{
ssize_t size;
size_t size;
if (!is_guest_ready(vrng)) {
return;
}
size = pop_an_elem(vrng);
size = get_request_size(vrng->vq);
size = MIN(vrng->quota_remaining, size);
if (size > 0) {
if (size) {
rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
}
}
static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
{
VirtIORNG *vrng = DO_UPCAST(VirtIORNG, vdev, vdev);
@ -131,23 +120,6 @@ static void virtio_rng_save(QEMUFile *f, void *opaque)
VirtIORNG *vrng = opaque;
virtio_save(&vrng->vdev, f);
qemu_put_byte(f, vrng->popped);
if (vrng->popped) {
int i;
qemu_put_be32(f, vrng->elem.index);
qemu_put_be32(f, vrng->elem.in_num);
for (i = 0; i < vrng->elem.in_num; i++) {
qemu_put_be64(f, vrng->elem.in_addr[i]);
}
qemu_put_be32(f, vrng->elem.out_num);
for (i = 0; i < vrng->elem.out_num; i++) {
qemu_put_be64(f, vrng->elem.out_addr[i]);
}
}
}
static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
@ -159,30 +131,6 @@ static int virtio_rng_load(QEMUFile *f, void *opaque, int version_id)
}
virtio_load(&vrng->vdev, f);
vrng->popped = qemu_get_byte(f);
if (vrng->popped) {
int i;
vrng->elem.index = qemu_get_be32(f);
vrng->elem.in_num = qemu_get_be32(f);
g_assert(vrng->elem.in_num < VIRTQUEUE_MAX_SIZE);
for (i = 0; i < vrng->elem.in_num; i++) {
vrng->elem.in_addr[i] = qemu_get_be64(f);
}
vrng->elem.out_num = qemu_get_be32(f);
g_assert(vrng->elem.out_num < VIRTQUEUE_MAX_SIZE);
for (i = 0; i < vrng->elem.out_num; i++) {
vrng->elem.out_addr[i] = qemu_get_be64(f);
}
virtqueue_map_sg(vrng->elem.in_sg, vrng->elem.in_addr,
vrng->elem.in_num, 1);
virtqueue_map_sg(vrng->elem.out_sg, vrng->elem.out_addr,
vrng->elem.out_num, 0);
}
/* We may have an element ready but couldn't process it due to a quota
limit. Make sure to try again after live migration when the quota may
have been reset.
@ -232,7 +180,7 @@ VirtIODevice *virtio_rng_init(DeviceState *dev, VirtIORNGConf *conf)
vrng->qdev = dev;
vrng->conf = conf;
vrng->popped = false;
vrng->quota_remaining = vrng->conf->max_bytes;
g_assert_cmpint(vrng->conf->max_bytes, <=, INT64_MAX);