Devices may have component devices and buses. Device realization may fail. Realization is recursive: a device's realize() method realizes its components, and device_set_realized() realizes its buses (which should in turn realize the devices on that bus, except bus_set_realized() doesn't implement that, yet). When realization of a component or bus fails, we need to roll back: unrealize everything we realized so far. If any of these unrealizes failed, the device would be left in an inconsistent state. Must not happen. device_set_realized() lets it happen: it ignores errors in the roll back code starting at label child_realize_fail. Since realization is recursive, unrealization must be recursive, too. But how could a partly failed unrealize be rolled back? We'd have to re-realize, which can fail. This design is fundamentally broken. device_set_realized() does not roll back at all. Instead, it keeps unrealizing, ignoring further errors. It can screw up even for a device with no buses: if the lone dc->unrealize() fails, it still unregisters vmstate, and calls listeners' unrealize() callback. bus_set_realized() does not roll back either. Instead, it stops unrealizing. Fortunately, no unrealize method can fail, as we'll see below. To fix the design error, drop parameter @errp from all the unrealize methods. Any unrealize method that uses @errp now needs an update. This leads us to unrealize() methods that can fail. Merely passing it to another unrealize method cannot cause failure, though. Here are the ones that do other things with @errp: * virtio_serial_device_unrealize() Fails when qbus_set_hotplug_handler() fails, but still does all the other work. On failure, the device would stay realized with its resources completely gone. Oops. Can't happen, because qbus_set_hotplug_handler() can't actually fail here. Pass &error_abort to qbus_set_hotplug_handler() instead. * hw/ppc/spapr_drc.c's unrealize() Fails when object_property_del() fails, but all the other work is already done. On failure, the device would stay realized with its vmstate registration gone. Oops. Can't happen, because object_property_del() can't actually fail here. Pass &error_abort to object_property_del() instead. * spapr_phb_unrealize() Fails and bails out when remove_drcs() fails, but other work is already done. On failure, the device would stay realized with some of its resources gone. Oops. remove_drcs() fails only when chassis_from_bus()'s object_property_get_uint() fails, and it can't here. Pass &error_abort to remove_drcs() instead. Therefore, no unrealize method can fail before this patch. device_set_realized()'s recursive unrealization via bus uses object_property_set_bool(). Can't drop @errp there, so pass &error_abort. We similarly unrealize with object_property_set_bool() elsewhere, always ignoring errors. Pass &error_abort instead. Several unrealize methods no longer handle errors from other unrealize methods: virtio_9p_device_unrealize(), virtio_input_device_unrealize(), scsi_qdev_unrealize(), ... Much of the deleted error handling looks wrong anyway. One unrealize methods no longer ignore such errors: usb_ehci_pci_exit(). Several realize methods no longer ignore errors when rolling back: v9fs_device_realize_common(), pci_qdev_unrealize(), spapr_phb_realize(), usb_qdev_realize(), vfio_ccw_realize(), virtio_device_realize(). Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20200505152926.18877-17-armbru@redhat.com>
294 lines
8.1 KiB
C
294 lines
8.1 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 "qemu/module.h"
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#include "qemu/timer.h"
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#include "hw/virtio/virtio.h"
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#include "hw/qdev-properties.h"
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#include "hw/virtio/virtio-rng.h"
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#include "sysemu/rng.h"
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#include "sysemu/runstate.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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Object *default_backend = object_new(TYPE_RNG_BUILTIN);
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user_creatable_complete(USER_CREATABLE(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(default_backend);
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return;
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}
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object_property_add_child(OBJECT(dev), "default-backend",
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default_backend);
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/* The child property took a reference, we can safely drop ours now */
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object_unref(default_backend);
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object_property_set_link(OBJECT(dev), default_backend,
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"rng", &error_abort);
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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)
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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_del_queue(vdev, 0);
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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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device_class_set_props(dc, 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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