virtio-rng device causes old guest kernels(2.6.32) to hang on latest qemu. The driver attempts to read from the virtio-rng device too early in it's initialization. Qemu detects guest is not ready and returns, resulting in hang. To fix handle pending requests when guest is running and driver status is set to 'VIRTIO_CONFIG_S_DRIVER_OK'. CC: qemu-stable@nongnu.org Reported-by: Sergio lopez <slopezpa@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Pankaj Gupta <pagupta@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
293 lines
8.2 KiB
C
293 lines
8.2 KiB
C
/*
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* A virtio device implementing a hardware random number generator.
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*
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* Copyright 2012 Red Hat, Inc.
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* Copyright 2012 Amit Shah <amit.shah@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or
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* (at your option) any later version. See the COPYING file in the
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* top-level directory.
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*/
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#include "qemu/osdep.h"
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#include "qapi/error.h"
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#include "qemu/iov.h"
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#include "hw/qdev.h"
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#include "hw/virtio/virtio.h"
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#include "hw/virtio/virtio-rng.h"
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#include "sysemu/rng.h"
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#include "qom/object_interfaces.h"
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#include "trace.h"
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static bool is_guest_ready(VirtIORNG *vrng)
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{
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VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
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if (virtio_queue_ready(vrng->vq)
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&& (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
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return true;
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}
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trace_virtio_rng_guest_not_ready(vrng);
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return false;
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}
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static size_t get_request_size(VirtQueue *vq, unsigned quota)
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{
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unsigned int in, out;
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virtqueue_get_avail_bytes(vq, &in, &out, quota, 0);
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return in;
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}
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static void virtio_rng_process(VirtIORNG *vrng);
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/* Send data from a char device over to the guest */
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static void chr_read(void *opaque, const void *buf, size_t size)
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{
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VirtIORNG *vrng = opaque;
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VirtIODevice *vdev = VIRTIO_DEVICE(vrng);
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VirtQueueElement *elem;
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size_t len;
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int offset;
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if (!is_guest_ready(vrng)) {
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return;
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}
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/* we can't modify the virtqueue until
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* our state is fully synced
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*/
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if (!runstate_check(RUN_STATE_RUNNING)) {
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trace_virtio_rng_cpu_is_stopped(vrng, size);
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return;
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}
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vrng->quota_remaining -= size;
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offset = 0;
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while (offset < size) {
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elem = virtqueue_pop(vrng->vq, sizeof(VirtQueueElement));
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if (!elem) {
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break;
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}
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trace_virtio_rng_popped(vrng);
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len = iov_from_buf(elem->in_sg, elem->in_num,
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0, buf + offset, size - offset);
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offset += len;
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virtqueue_push(vrng->vq, elem, len);
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trace_virtio_rng_pushed(vrng, len);
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g_free(elem);
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}
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virtio_notify(vdev, vrng->vq);
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if (!virtio_queue_empty(vrng->vq)) {
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/* If we didn't drain the queue, call virtio_rng_process
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* to take care of asking for more data as appropriate.
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*/
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virtio_rng_process(vrng);
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}
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}
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static void virtio_rng_process(VirtIORNG *vrng)
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{
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size_t size;
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unsigned quota;
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if (!is_guest_ready(vrng)) {
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return;
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}
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if (vrng->activate_timer) {
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timer_mod(vrng->rate_limit_timer,
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qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + vrng->conf.period_ms);
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vrng->activate_timer = false;
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}
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if (vrng->quota_remaining < 0) {
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quota = 0;
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} else {
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quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX);
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}
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size = get_request_size(vrng->vq, quota);
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trace_virtio_rng_request(vrng, size, quota);
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size = MIN(vrng->quota_remaining, size);
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if (size) {
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rng_backend_request_entropy(vrng->rng, size, chr_read, vrng);
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}
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}
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static void handle_input(VirtIODevice *vdev, VirtQueue *vq)
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{
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VirtIORNG *vrng = VIRTIO_RNG(vdev);
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virtio_rng_process(vrng);
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}
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static uint64_t get_features(VirtIODevice *vdev, uint64_t f, Error **errp)
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{
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return f;
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}
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static void virtio_rng_vm_state_change(void *opaque, int running,
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RunState state)
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{
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VirtIORNG *vrng = opaque;
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trace_virtio_rng_vm_state_change(vrng, running, state);
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/* We may have an element ready but couldn't process it due to a quota
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* limit or because CPU was stopped. Make sure to try again when the
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* CPU restart.
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*/
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if (running && is_guest_ready(vrng)) {
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virtio_rng_process(vrng);
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}
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}
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static void check_rate_limit(void *opaque)
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{
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VirtIORNG *vrng = opaque;
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vrng->quota_remaining = vrng->conf.max_bytes;
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virtio_rng_process(vrng);
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vrng->activate_timer = true;
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}
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static void virtio_rng_set_status(VirtIODevice *vdev, uint8_t status)
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{
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VirtIORNG *vrng = VIRTIO_RNG(vdev);
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if (!vdev->vm_running) {
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return;
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}
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vdev->status = status;
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/* Something changed, try to process buffers */
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virtio_rng_process(vrng);
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}
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static void virtio_rng_device_realize(DeviceState *dev, Error **errp)
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{
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VirtIODevice *vdev = VIRTIO_DEVICE(dev);
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VirtIORNG *vrng = VIRTIO_RNG(dev);
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Error *local_err = NULL;
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if (vrng->conf.period_ms <= 0) {
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error_setg(errp, "'period' parameter expects a positive integer");
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return;
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}
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/* Workaround: Property parsing does not enforce unsigned integers,
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* So this is a hack to reject such numbers. */
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if (vrng->conf.max_bytes > INT64_MAX) {
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error_setg(errp, "'max-bytes' parameter must be non-negative, "
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"and less than 2^63");
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return;
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}
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if (vrng->conf.rng == NULL) {
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vrng->conf.default_backend = RNG_RANDOM(object_new(TYPE_RNG_RANDOM));
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user_creatable_complete(OBJECT(vrng->conf.default_backend),
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&local_err);
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if (local_err) {
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error_propagate(errp, local_err);
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object_unref(OBJECT(vrng->conf.default_backend));
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return;
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}
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object_property_add_child(OBJECT(dev),
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"default-backend",
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OBJECT(vrng->conf.default_backend),
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NULL);
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/* The child property took a reference, we can safely drop ours now */
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object_unref(OBJECT(vrng->conf.default_backend));
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object_property_set_link(OBJECT(dev),
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OBJECT(vrng->conf.default_backend),
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"rng", NULL);
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}
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vrng->rng = vrng->conf.rng;
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if (vrng->rng == NULL) {
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error_setg(errp, "'rng' parameter expects a valid object");
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return;
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}
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virtio_init(vdev, "virtio-rng", VIRTIO_ID_RNG, 0);
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vrng->vq = virtio_add_queue(vdev, 8, handle_input);
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vrng->quota_remaining = vrng->conf.max_bytes;
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vrng->rate_limit_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
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check_rate_limit, vrng);
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vrng->activate_timer = true;
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vrng->vmstate = qemu_add_vm_change_state_handler(virtio_rng_vm_state_change,
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vrng);
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}
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static void virtio_rng_device_unrealize(DeviceState *dev, Error **errp)
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{
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VirtIODevice *vdev = VIRTIO_DEVICE(dev);
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VirtIORNG *vrng = VIRTIO_RNG(dev);
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qemu_del_vm_change_state_handler(vrng->vmstate);
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timer_del(vrng->rate_limit_timer);
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timer_free(vrng->rate_limit_timer);
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virtio_cleanup(vdev);
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}
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static const VMStateDescription vmstate_virtio_rng = {
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.name = "virtio-rng",
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.minimum_version_id = 1,
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.version_id = 1,
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.fields = (VMStateField[]) {
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VMSTATE_VIRTIO_DEVICE,
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VMSTATE_END_OF_LIST()
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},
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};
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static Property virtio_rng_properties[] = {
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/* Set a default rate limit of 2^47 bytes per minute or roughly 2TB/s. If
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* you have an entropy source capable of generating more entropy than this
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* and you can pass it through via virtio-rng, then hats off to you. Until
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* then, this is unlimited for all practical purposes.
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*/
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DEFINE_PROP_UINT64("max-bytes", VirtIORNG, conf.max_bytes, INT64_MAX),
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DEFINE_PROP_UINT32("period", VirtIORNG, conf.period_ms, 1 << 16),
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DEFINE_PROP_LINK("rng", VirtIORNG, conf.rng, TYPE_RNG_BACKEND, RngBackend *),
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DEFINE_PROP_END_OF_LIST(),
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};
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static void virtio_rng_class_init(ObjectClass *klass, void *data)
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{
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DeviceClass *dc = DEVICE_CLASS(klass);
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VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
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dc->props = virtio_rng_properties;
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dc->vmsd = &vmstate_virtio_rng;
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set_bit(DEVICE_CATEGORY_MISC, dc->categories);
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vdc->realize = virtio_rng_device_realize;
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vdc->unrealize = virtio_rng_device_unrealize;
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vdc->get_features = get_features;
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vdc->set_status = virtio_rng_set_status;
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}
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static const TypeInfo virtio_rng_info = {
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.name = TYPE_VIRTIO_RNG,
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.parent = TYPE_VIRTIO_DEVICE,
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.instance_size = sizeof(VirtIORNG),
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.class_init = virtio_rng_class_init,
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};
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static void virtio_register_types(void)
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{
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type_register_static(&virtio_rng_info);
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}
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type_init(virtio_register_types)
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