On Fri, Dec 08, 2017 at 05:54:18PM +0300, Ilya Maximets wrote: > On 07.12.2017 20:27, Michael S. Tsirkin wrote: > > On Thu, Dec 07, 2017 at 09:39:36AM +0300, Ilya Maximets wrote: > >> On 06.12.2017 19:45, Michael S. Tsirkin wrote: > >>> On Wed, Dec 06, 2017 at 04:06:18PM +0300, Ilya Maximets wrote: > >>>> In case virtio error occured after vhost_dev_close(), qemu will crash > >>>> in nested cleanup while checking IOMMU flag because dev->vdev already > >>>> set to zero and resources are already freed. > >>>> > >>>> Example: > >>>> > >>>> Program received signal SIGSEGV, Segmentation fault. > >>>> vhost_virtqueue_stop at hw/virtio/vhost.c:1155 > >>>> > >>>> #0 vhost_virtqueue_stop at hw/virtio/vhost.c:1155 > >>>> #1 vhost_dev_stop at hw/virtio/vhost.c:1594 > >>>> #2 vhost_net_stop_one at hw/net/vhost_net.c:289 > >>>> #3 vhost_net_stop at hw/net/vhost_net.c:368 > >>>> > >>>> Nested call to vhost_net_stop(). First time was at #14. > >>>> > >>>> #4 virtio_net_vhost_status at hw/net/virtio-net.c:180 > >>>> #5 virtio_net_set_status (status=79) at hw/net/virtio-net.c:254 > >>>> #6 virtio_set_status at hw/virtio/virtio.c:1146 > >>>> #7 virtio_error at hw/virtio/virtio.c:2455 > >>>> > >>>> virtqueue_get_head() failed here. > >>>> > >>>> #8 virtqueue_get_head at hw/virtio/virtio.c:543 > >>>> #9 virtqueue_drop_all at hw/virtio/virtio.c:984 > >>>> #10 virtio_net_drop_tx_queue_data at hw/net/virtio-net.c:240 > >>>> #11 virtio_bus_set_host_notifier at hw/virtio/virtio-bus.c:297 > >>>> #12 vhost_dev_disable_notifiers at hw/virtio/vhost.c:1431 > >>>> > >>>> vhost_dev_stop() was executed here. dev->vdev == NULL now. > >>>> > >>>> #13 vhost_net_stop_one at hw/net/vhost_net.c:290 > >>>> #14 vhost_net_stop at hw/net/vhost_net.c:368 > >>>> #15 virtio_net_vhost_status at hw/net/virtio-net.c:180 > >>>> #16 virtio_net_set_status (status=15) at hw/net/virtio-net.c:254 > >>>> #17 qmp_set_link ("hostnet0", up=false) at net/net.c:1430 > >>>> #18 chr_closed_bh at net/vhost-user.c:214 > >>>> #19 aio_bh_call at util/async.c:90 > >>>> #20 aio_bh_poll at util/async.c:118 > >>>> #21 aio_dispatch at util/aio-posix.c:429 > >>>> #22 aio_ctx_dispatch at util/async.c:261 > >>>> #23 g_main_context_dispatch > >>>> #24 glib_pollfds_poll at util/main-loop.c:213 > >>>> #25 os_host_main_loop_wait at util/main-loop.c:261 > >>>> #26 main_loop_wait at util/main-loop.c:515 > >>>> #27 main_loop () at vl.c:1917 > >>>> #28 main at vl.c:4795 > >>>> > >>>> Above backtrace captured from qemu crash on vhost disconnect while > >>>> virtio driver in guest was in failed state. > >>>> > >>>> We can just add checking for 'vdev' in 'vhost_dev_has_iommu()' but > >>>> it will assert further trying to free already freed ioeventfds. The > >>>> real problem is that we're allowing nested calls to 'vhost_net_stop'. > >>>> > >>>> This patch is aimed to forbid nested calls to 'vhost_net_stop' to avoid > >>>> any possible double frees and segmentation faults doue to using of > >>>> already freed resources by setting 'vhost_started' flag to zero prior > >>>> to 'vhost_net_stop' call. > >>>> > >>>> Signed-off-by: Ilya Maximets <i.maxim...@samsung.com> > >>>> --- > >>>> > >>>> This issue was already addressed more than a year ago by the following > >>>> patch: > >>>> https://lists.gnu.org/archive/html/qemu-devel/2016-03/msg06732.html > >>>> but it was dropped without review due to not yet implemented > >>>> re-connection > >>>> of vhost-user. Re-connection implementation lately fixed most of the > >>>> nested calls, but few of them still exists. For example, above backtrace > >>>> captured after 'virtqueue_get_head()' failure on vhost-user > >>>> disconnection. > >>>> > >>>> hw/net/virtio-net.c | 2 +- > >>>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>>> > >>>> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > >>>> index 38674b0..4d95a18 100644 > >>>> --- a/hw/net/virtio-net.c > >>>> +++ b/hw/net/virtio-net.c > >>>> @@ -177,8 +177,8 @@ static void virtio_net_vhost_status(VirtIONet *n, > >>>> uint8_t status) > >>>> n->vhost_started = 0; > >>>> } > >>>> } else { > >>>> - vhost_net_stop(vdev, n->nic->ncs, queues); > >>>> n->vhost_started = 0; > >>>> + vhost_net_stop(vdev, n->nic->ncs, queues); > >>>> } > >>>> } > >>> > >>> Well the wider context is > >>> > >>> > >>> n->vhost_started = 1; > >>> r = vhost_net_start(vdev, n->nic->ncs, queues); > >>> if (r < 0) { > >>> error_report("unable to start vhost net: %d: " > >>> "falling back on userspace virtio", -r); > >>> n->vhost_started = 0; > >>> } > >>> } else { > >>> vhost_net_stop(vdev, n->nic->ncs, queues); > >>> n->vhost_started = 0; > >>> > >>> So we set it to 1 before start, we should clear after stop. > >> > >> OK. I agree that clearing after is a bit safer. But in this case we need > >> a separate flag or other way to detect that we're already inside the > >> 'vhost_net_stop()'. > >> > >> What do you think about that old patch: > >> https://lists.gnu.org/archive/html/qemu-devel/2016-03/msg06732.html ? > >> > >> It implements the same thing but introduces additional flag. It even could > >> be still applicable. > > > > So the issue is that if someone calls set_status nested > > from within set_status, then status gets over-written > > because status is only set at the last moment, > > it's thus actually incorrect most of the time. > > > > But most people just want the new status, > > so it is better to keep that as part of status. > > > > I think something like the following should do the trick. > > Thoughts? > > Maybe you're right, but it's really hard to understand the patch below. > The function 'set_status' doesn't set the status anymore, instead we > need to set status manually before calling the 'set_status'.
I don't understand this comment. status is set in virtio_set_status, same as it was previously. set_status is a callback. The issue was that if set_status callback changed the status again, it would overwrite the old value. Fix is to firsdt set status then do a callback. This means we can not pass new value as parameter any longer. We pass the old one, new value is in vdev->status. It's true that virtio_net_set_status checks vdev->status now, so it must be set correctly on unrealize. > That > looks very strange. Some of the functions gets 'old_status', others > the 'new_status'. I'm a bit confused. OK, fair enough. Fixed - let's pass old status everywhere, users that need the new one can get it from the vdev. > And it's not functional in current state: > > hw/net/virtio-net.c:264:28: error: ‘status’ undeclared Fixed too. new version below. > > > > Signed-off-by: Michael S. Tsirkin <m...@redhat.com> Still completely untested, sorry about that - hope you can help here. diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h index 098bdaa..f5d0ee1 100644 --- a/include/hw/virtio/virtio.h +++ b/include/hw/virtio/virtio.h @@ -115,7 +115,7 @@ typedef struct VirtioDeviceClass { void (*get_config)(VirtIODevice *vdev, uint8_t *config); void (*set_config)(VirtIODevice *vdev, const uint8_t *config); void (*reset)(VirtIODevice *vdev); - void (*set_status)(VirtIODevice *vdev, uint8_t val); + void (*set_status)(VirtIODevice *vdev, uint8_t old_status); /* For transitional devices, this is a bitmap of features * that are only exposed on the legacy interface but not * the modern one. diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index 05d1440..b8b07ba 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -814,15 +814,15 @@ static uint64_t virtio_blk_get_features(VirtIODevice *vdev, uint64_t features, return features; } -static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status) +static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t old_status) { VirtIOBlock *s = VIRTIO_BLK(vdev); - if (!(status & (VIRTIO_CONFIG_S_DRIVER | VIRTIO_CONFIG_S_DRIVER_OK))) { + if (!(vdev->status & (VIRTIO_CONFIG_S_DRIVER | VIRTIO_CONFIG_S_DRIVER_OK))) { assert(!s->dataplane_started); } - if (!(status & VIRTIO_CONFIG_S_DRIVER_OK)) { + if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) { return; } diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c index 9470bd7..881b1ff 100644 --- a/hw/char/virtio-serial-bus.c +++ b/hw/char/virtio-serial-bus.c @@ -616,7 +616,7 @@ static void guest_reset(VirtIOSerial *vser) } } -static void set_status(VirtIODevice *vdev, uint8_t status) +static void set_status(VirtIODevice *vdev, uint8_t old_status) { VirtIOSerial *vser; VirtIOSerialPort *port; @@ -625,7 +625,7 @@ static void set_status(VirtIODevice *vdev, uint8_t status) port = find_port_by_id(vser, 0); if (port && !use_multiport(port->vser) - && (status & VIRTIO_CONFIG_S_DRIVER_OK)) { + && (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) { /* * Non-multiport guests won't be able to tell us guest * open/close status. Such guests can only have a port at id @@ -634,7 +634,7 @@ static void set_status(VirtIODevice *vdev, uint8_t status) */ port->guest_connected = true; } - if (!(status & VIRTIO_CONFIG_S_DRIVER_OK)) { + if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) { guest_reset(vser); } diff --git a/hw/input/virtio-input.c b/hw/input/virtio-input.c index 0e42f0d..abb817b 100644 --- a/hw/input/virtio-input.c +++ b/hw/input/virtio-input.c @@ -188,12 +188,12 @@ static uint64_t virtio_input_get_features(VirtIODevice *vdev, uint64_t f, return f; } -static void virtio_input_set_status(VirtIODevice *vdev, uint8_t val) +static void virtio_input_set_status(VirtIODevice *vdev, uint8_t old_val) { VirtIOInputClass *vic = VIRTIO_INPUT_GET_CLASS(vdev); VirtIOInput *vinput = VIRTIO_INPUT(vdev); - if (val & VIRTIO_CONFIG_S_DRIVER_OK) { + if (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) { if (!vinput->active) { vinput->active = true; if (vic->change_active) { diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index 38674b0..7851968 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -124,7 +124,7 @@ static void virtio_net_announce_timer(void *opaque) virtio_notify_config(vdev); } -static void virtio_net_vhost_status(VirtIONet *n, uint8_t status) +static void virtio_net_vhost_status(VirtIONet *n, uint8_t old_status) { VirtIODevice *vdev = VIRTIO_DEVICE(n); NetClientState *nc = qemu_get_queue(n->nic); @@ -134,7 +134,7 @@ static void virtio_net_vhost_status(VirtIONet *n, uint8_t status) return; } - if ((virtio_net_started(n, status) && !nc->peer->link_down) == + if ((virtio_net_started(n, vdev->status) && !nc->peer->link_down) == !!n->vhost_started) { return; } @@ -212,12 +212,12 @@ static bool virtio_net_set_vnet_endian(VirtIODevice *vdev, NetClientState *ncs, return false; } -static void virtio_net_vnet_endian_status(VirtIONet *n, uint8_t status) +static void virtio_net_vnet_endian_status(VirtIONet *n, uint8_t old_status) { VirtIODevice *vdev = VIRTIO_DEVICE(n); int queues = n->multiqueue ? n->max_queues : 1; - if (virtio_net_started(n, status)) { + if (virtio_net_started(n, vdev->status)) { /* Before using the device, we tell the network backend about the * endianness to use when parsing vnet headers. If the backend * can't do it, we fallback onto fixing the headers in the core @@ -225,7 +225,7 @@ static void virtio_net_vnet_endian_status(VirtIONet *n, uint8_t status) */ n->needs_vnet_hdr_swap = virtio_net_set_vnet_endian(vdev, n->nic->ncs, queues, true); - } else if (virtio_net_started(n, vdev->status)) { + } else if (virtio_net_started(n, old_status)) { /* After using the device, we need to reset the network backend to * the default (guest native endianness), otherwise the guest may * lose network connectivity if it is rebooted into a different @@ -243,15 +243,15 @@ static void virtio_net_drop_tx_queue_data(VirtIODevice *vdev, VirtQueue *vq) } } -static void virtio_net_set_status(struct VirtIODevice *vdev, uint8_t status) +static void virtio_net_set_status(struct VirtIODevice *vdev, uint8_t old_status) { VirtIONet *n = VIRTIO_NET(vdev); VirtIONetQueue *q; int i; uint8_t queue_status; - virtio_net_vnet_endian_status(n, status); - virtio_net_vhost_status(n, status); + virtio_net_vnet_endian_status(n, old_status); + virtio_net_vhost_status(n, old_status); for (i = 0; i < n->max_queues; i++) { NetClientState *ncs = qemu_get_subqueue(n->nic, i); @@ -261,7 +261,7 @@ static void virtio_net_set_status(struct VirtIODevice *vdev, uint8_t status) if ((!n->multiqueue && i != 0) || i >= n->curr_queues) { queue_status = 0; } else { - queue_status = status; + queue_status = vdev->status; } queue_started = virtio_net_started(n, queue_status) && !n->vhost_started; @@ -2048,9 +2048,11 @@ static void virtio_net_device_unrealize(DeviceState *dev, Error **errp) VirtIODevice *vdev = VIRTIO_DEVICE(dev); VirtIONet *n = VIRTIO_NET(dev); int i, max_queues; + uint8_t old_status = vdev->status; /* This will stop vhost backend if appropriate. */ - virtio_net_set_status(vdev, 0); + vdev->status = 0; + virtio_net_set_status(vdev, old_status); g_free(n->netclient_name); n->netclient_name = NULL; diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c index 9c1bea8..5a561e4 100644 --- a/hw/scsi/vhost-scsi.c +++ b/hw/scsi/vhost-scsi.c @@ -108,11 +108,11 @@ static void vhost_scsi_stop(VHostSCSI *s) vhost_scsi_common_stop(vsc); } -static void vhost_scsi_set_status(VirtIODevice *vdev, uint8_t val) +static void vhost_scsi_set_status(VirtIODevice *vdev, uint8_t old_val) { VHostSCSI *s = VHOST_SCSI(vdev); VHostSCSICommon *vsc = VHOST_SCSI_COMMON(s); - bool start = (val & VIRTIO_CONFIG_S_DRIVER_OK); + bool start = vdev->status & VIRTIO_CONFIG_S_DRIVER_OK; if (vsc->dev.started == start) { return; diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c index f7561e2..289a27e 100644 --- a/hw/scsi/vhost-user-scsi.c +++ b/hw/scsi/vhost-user-scsi.c @@ -38,11 +38,11 @@ static const int user_feature_bits[] = { VHOST_INVALID_FEATURE_BIT }; -static void vhost_user_scsi_set_status(VirtIODevice *vdev, uint8_t status) +static void vhost_user_scsi_set_status(VirtIODevice *vdev, uint8_t old_status) { VHostUserSCSI *s = (VHostUserSCSI *)vdev; VHostSCSICommon *vsc = VHOST_SCSI_COMMON(s); - bool start = (status & VIRTIO_CONFIG_S_DRIVER_OK) && vdev->vm_running; + bool start = (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) && vdev->vm_running; if (vsc->dev.started == start) { return; diff --git a/hw/virtio/vhost-vsock.c b/hw/virtio/vhost-vsock.c index 5ec1c6a..d3f445b 100644 --- a/hw/virtio/vhost-vsock.c +++ b/hw/virtio/vhost-vsock.c @@ -154,10 +154,10 @@ static void vhost_vsock_stop(VirtIODevice *vdev) vhost_dev_disable_notifiers(&vsock->vhost_dev, vdev); } -static void vhost_vsock_set_status(VirtIODevice *vdev, uint8_t status) +static void vhost_vsock_set_status(VirtIODevice *vdev, uint8_t old_status) { VHostVSock *vsock = VHOST_VSOCK(vdev); - bool should_start = status & VIRTIO_CONFIG_S_DRIVER_OK; + bool should_start = vdev->status & VIRTIO_CONFIG_S_DRIVER_OK; if (!vdev->vm_running) { should_start = false; @@ -370,11 +370,14 @@ static void vhost_vsock_device_unrealize(DeviceState *dev, Error **errp) { VirtIODevice *vdev = VIRTIO_DEVICE(dev); VHostVSock *vsock = VHOST_VSOCK(dev); + uint8_t old_status; vhost_vsock_post_load_timer_cleanup(vsock); /* This will stop vhost backend if appropriate. */ - vhost_vsock_set_status(vdev, 0); + old_status = vdev->status; + vdev->status = 0; + vhost_vsock_set_status(vdev, old_status); vhost_dev_cleanup(&vsock->vhost_dev); virtio_cleanup(vdev); diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c index 37cde38..84e897a 100644 --- a/hw/virtio/virtio-balloon.c +++ b/hw/virtio/virtio-balloon.c @@ -468,12 +468,12 @@ static void virtio_balloon_device_reset(VirtIODevice *vdev) } } -static void virtio_balloon_set_status(VirtIODevice *vdev, uint8_t status) +static void virtio_balloon_set_status(VirtIODevice *vdev, uint8_t old_status) { VirtIOBalloon *s = VIRTIO_BALLOON(vdev); if (!s->stats_vq_elem && vdev->vm_running && - (status & VIRTIO_CONFIG_S_DRIVER_OK) && virtqueue_rewind(s->svq, 1)) { + (vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) && virtqueue_rewind(s->svq, 1)) { /* poll stats queue for the element we have discarded when the VM * was stopped */ virtio_balloon_receive_stats(vdev, s->svq); diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index ad564b0..4981858 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -1128,6 +1128,8 @@ static int virtio_validate_features(VirtIODevice *vdev) int virtio_set_status(VirtIODevice *vdev, uint8_t val) { VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev); + uint8_t old_status; + trace_virtio_set_status(vdev, val); if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) { @@ -1140,10 +1142,13 @@ int virtio_set_status(VirtIODevice *vdev, uint8_t val) } } } + + old_status = vdev->status; + vdev->status = val; + if (k->set_status) { - k->set_status(vdev, val); + k->set_status(vdev, old_status); } - vdev->status = val; return 0; }