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[Qemu-devel] [PATCH v3 03/10] virtio: stop virtqueue processing if devic
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH v3 03/10] virtio: stop virtqueue processing if device is broken |
Date: |
Tue, 12 Apr 2016 14:25:27 +0100 |
QEMU prints an error message and exits when the device enters an invalid
state. Terminating the process is heavy-handed. The guest may still be
able to function even if there is a bug in a virtio guest driver.
Moreover, exiting is a bug in nested virtualization where a nested guest
could DoS other nested guests by killing a pass-through virtio device.
I don't think this configuration is possible today but it is likely in
the future.
If the broken flag is set, do not process virtqueues or write back used
descriptors. The broken flag can be cleared again by resetting the
device.
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
hw/virtio/virtio.c | 39 +++++++++++++++++++++++++++++++++++++++
include/hw/virtio/virtio.h | 3 +++
2 files changed, 42 insertions(+)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 02c71a2..cedda4b 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -279,6 +279,10 @@ void virtqueue_fill(VirtQueue *vq, const VirtQueueElement
*elem,
virtqueue_unmap_sg(vq, elem, len);
+ if (unlikely(vq->vdev->broken)) {
+ return;
+ }
+
idx = (idx + vq->used_idx) % vq->vring.num;
uelem.id = elem->index;
@@ -289,6 +293,12 @@ void virtqueue_fill(VirtQueue *vq, const VirtQueueElement
*elem,
void virtqueue_flush(VirtQueue *vq, unsigned int count)
{
uint16_t old, new;
+
+ if (unlikely(vq->vdev->broken)) {
+ vq->inuse -= count;
+ return;
+ }
+
/* Make sure buffer is written before we update index. */
smp_wmb();
trace_virtqueue_flush(vq, count);
@@ -549,6 +559,9 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz)
struct iovec iov[VIRTQUEUE_MAX_SIZE];
VRingDesc desc;
+ if (unlikely(vdev->broken)) {
+ return NULL;
+ }
if (virtio_queue_empty(vq)) {
return NULL;
}
@@ -708,6 +721,10 @@ static void virtio_notify_vector(VirtIODevice *vdev,
uint16_t vector)
BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+ if (unlikely(vdev->broken)) {
+ return;
+ }
+
if (k->notify) {
k->notify(qbus->parent, vector);
}
@@ -791,6 +808,7 @@ void virtio_reset(void *opaque)
k->reset(vdev);
}
+ vdev->broken = false;
vdev->guest_features = 0;
vdev->queue_sel = 0;
vdev->status = 0;
@@ -1104,6 +1122,10 @@ static void virtio_queue_notify_vq(VirtQueue *vq)
if (vq->vring.desc && vq->handle_output) {
VirtIODevice *vdev = vq->vdev;
+ if (unlikely(vdev->broken)) {
+ return;
+ }
+
trace_virtio_queue_notify(vdev, vq - vdev->vq, vq);
vq->handle_output(vdev, vq);
}
@@ -1675,6 +1697,7 @@ void virtio_init(VirtIODevice *vdev, const char *name,
vdev->config_vector = VIRTIO_NO_VECTOR;
vdev->vq = g_malloc0(sizeof(VirtQueue) * VIRTIO_QUEUE_MAX);
vdev->vm_running = runstate_is_running();
+ vdev->broken = false;
for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
vdev->vq[i].vector = VIRTIO_NO_VECTOR;
vdev->vq[i].vdev = vdev;
@@ -1852,6 +1875,22 @@ void virtio_device_set_child_bus_name(VirtIODevice
*vdev, char *bus_name)
vdev->bus_name = g_strdup(bus_name);
}
+void GCC_FMT_ATTR(2, 3) virtio_error(VirtIODevice *vdev, const char *fmt, ...)
+{
+ va_list ap;
+
+ va_start(ap, fmt);
+ error_vreport(fmt, ap);
+ va_end(ap);
+
+ vdev->broken = true;
+
+ if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
+ virtio_set_status(vdev, vdev->status | VIRTIO_CONFIG_S_NEEDS_RESET);
+ virtio_notify_config(vdev);
+ }
+}
+
static void virtio_device_realize(DeviceState *dev, Error **errp)
{
VirtIODevice *vdev = VIRTIO_DEVICE(dev);
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 6a37065..012b0d1 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -87,6 +87,7 @@ struct VirtIODevice
VirtQueue *vq;
uint16_t device_id;
bool vm_running;
+ bool broken; /* device in invalid state, needs reset */
VMChangeStateEntry *vmstate;
char *bus_name;
uint8_t device_endian;
@@ -135,6 +136,8 @@ void virtio_init(VirtIODevice *vdev, const char *name,
uint16_t device_id, size_t config_size);
void virtio_cleanup(VirtIODevice *vdev);
+void virtio_error(VirtIODevice *vdev, const char *fmt, ...) GCC_FMT_ATTR(2, 3);
+
/* Set the child bus name. */
void virtio_device_set_child_bus_name(VirtIODevice *vdev, char *bus_name);
--
2.5.5
- [Qemu-devel] [PATCH v3 00/10] virtio: avoid exit() when device enters invalid states, Stefan Hajnoczi, 2016/04/12
- [Qemu-devel] [PATCH v3 01/10] virtio: fix stray tab character, Stefan Hajnoczi, 2016/04/12
- [Qemu-devel] [PATCH v3 02/10] include: update virtio_config.h Linux header, Stefan Hajnoczi, 2016/04/12
- [Qemu-devel] [PATCH v3 03/10] virtio: stop virtqueue processing if device is broken,
Stefan Hajnoczi <=
- [Qemu-devel] [PATCH v3 04/10] virtio: migrate vdev->broken flag, Stefan Hajnoczi, 2016/04/12
- [Qemu-devel] [PATCH v3 05/10] virtio: handle virtqueue_map_desc() errors, Stefan Hajnoczi, 2016/04/12
- [Qemu-devel] [PATCH v3 06/10] virtio: handle virtqueue_get_avail_bytes() errors, Stefan Hajnoczi, 2016/04/12
- [Qemu-devel] [PATCH v3 07/10] virtio: use unsigned int for virtqueue_get_avail_bytes() index, Stefan Hajnoczi, 2016/04/12
- [Qemu-devel] [PATCH v3 08/10] virtio: handle virtqueue_read_next_desc() errors, Stefan Hajnoczi, 2016/04/12
- [Qemu-devel] [PATCH v3 09/10] virtio: handle virtqueue_num_heads() errors, Stefan Hajnoczi, 2016/04/12
- [Qemu-devel] [PATCH v3 10/10] virtio: handle virtqueue_get_head() errors, Stefan Hajnoczi, 2016/04/12