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| From: | Si-Wei Liu |
| Subject: | Re: [PATCH 4/7] virtio: don't read pending event on host notifier if disabled |
| Date: | Wed, 30 Mar 2022 09:40:46 -0700 |
| User-agent: | Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 |
On 3/30/2022 2:14 AM, Jason Wang wrote:
Apologies, an incorrect stack trace was pasted which actually came from patch #1. I will post a v2 with the corresponding one as below:On Wed, Mar 30, 2022 at 2:33 PM Si-Wei Liu <si-wei.liu@oracle.com> wrote:Previous commit prevents vhost-user and vhost-vdpa from using userland vq handler via disable_ioeventfd_handler. The same needs to be done for host notifier cleanup too, as the virtio_queue_host_notifier_read handler still tends to read pending event left behind on ioeventfd and attempts to handle outstanding kicks from QEMU userland vq. If vq handler is not disabled on cleanup, it may lead to sigsegv with recursive virtio_net_set_status call on the control vq: 0 0x00007f8ce3ff3387 in raise () at /lib64/libc.so.6 1 0x00007f8ce3ff4a78 in abort () at /lib64/libc.so.6 2 0x00007f8ce3fec1a6 in __assert_fail_base () at /lib64/libc.so.6 3 0x00007f8ce3fec252 in () at /lib64/libc.so.6 4 0x0000558f52d79421 in vhost_vdpa_get_vq_index (dev=<optimized out>, idx=<optimized out>) at ../hw/virtio/vhost-vdpa.c:563 5 0x0000558f52d79421 in vhost_vdpa_get_vq_index (dev=<optimized out>, idx=<optimized out>) at ../hw/virtio/vhost-vdpa.c:558 6 0x0000558f52d7329a in vhost_virtqueue_mask (hdev=0x558f55c01800, vdev=0x558f568f91f0, n=2, mask=<optimized out>) at ../hw/virtio/vhost.c:1557I feel it's probably a bug elsewhere e.g when we fail to start vhost-vDPA, it's the charge of the Qemu to poll host notifier and we will fallback to the userspace vq handler.
0 0x000055f800df1780 in qdev_get_parent_bus (dev=0x0) at ../hw/core/qdev.c:376 1 0x000055f800c68ad8 in virtio_bus_device_iommu_enabled (vdev=vdev@entry=0x0) at ../hw/virtio/virtio-bus.c:331 2 0x000055f800d70d7f in vhost_memory_unmap (dev=<optimized out>) at ../hw/virtio/vhost.c:318 3 0x000055f800d70d7f in vhost_memory_unmap (dev=<optimized out>, buffer=0x7fc19bec5240, len=2052, is_write=1, access_len=2052) at ../hw/virtio/vhost.c:336 4 0x000055f800d71867 in vhost_virtqueue_stop (dev=dev@entry=0x55f8037ccc30, vdev=vdev@entry=0x55f8044ec590, vq=0x55f8037cceb0, idx=0) at ../hw/virtio/vhost.c:1241 5 0x000055f800d7406c in vhost_dev_stop (hdev=hdev@entry=0x55f8037ccc30, vdev=vdev@entry=0x55f8044ec590) at ../hw/virtio/vhost.c:1839 6 0x000055f800bf00a7 in vhost_net_stop_one (net=0x55f8037ccc30, dev=0x55f8044ec590) at ../hw/net/vhost_net.c:315 7 0x000055f800bf0678 in vhost_net_stop (dev=dev@entry=0x55f8044ec590, ncs=0x55f80452bae0, data_queue_pairs=data_queue_pairs@entry=7, cvq=cvq@entry=1)
at ../hw/net/vhost_net.c:4238 0x000055f800d4e628 in virtio_net_set_status (status=<optimized out>, n=0x55f8044ec590) at ../hw/net/virtio-net.c:296 9 0x000055f800d4e628 in virtio_net_set_status (vdev=vdev@entry=0x55f8044ec590, status=15 '\017') at ../hw/net/virtio-net.c:370 10 0x000055f800d534d8 in virtio_net_handle_ctrl (iov_cnt=<optimized out>, iov=<optimized out>, cmd=0 '\000', n=0x55f8044ec590) at ../hw/net/virtio-net.c:1408 11 0x000055f800d534d8 in virtio_net_handle_ctrl (vdev=0x55f8044ec590, vq=0x7fc1a7e888d0) at ../hw/net/virtio-net.c:1452 12 0x000055f800d69f37 in virtio_queue_host_notifier_read (vq=0x7fc1a7e888d0) at ../hw/virtio/virtio.c:2331 13 0x000055f800d69f37 in virtio_queue_host_notifier_read (n=n@entry=0x7fc1a7e8894c) at ../hw/virtio/virtio.c:3575 14 0x000055f800c688e6 in virtio_bus_cleanup_host_notifier (bus=<optimized out>, n=n@entry=14) at ../hw/virtio/virtio-bus.c:312 15 0x000055f800d73106 in vhost_dev_disable_notifiers (hdev=hdev@entry=0x55f8035b51b0, vdev=vdev@entry=0x55f8044ec590)
at ../../../include/hw/virtio/virtio-bus.h:3516 0x000055f800bf00b2 in vhost_net_stop_one (net=0x55f8035b51b0, dev=0x55f8044ec590) at ../hw/net/vhost_net.c:316 17 0x000055f800bf0678 in vhost_net_stop (dev=dev@entry=0x55f8044ec590, ncs=0x55f80452bae0, data_queue_pairs=data_queue_pairs@entry=7, cvq=cvq@entry=1)
at ../hw/net/vhost_net.c:42318 0x000055f800d4e628 in virtio_net_set_status (status=<optimized out>, n=0x55f8044ec590) at ../hw/net/virtio-net.c:296 19 0x000055f800d4e628 in virtio_net_set_status (vdev=0x55f8044ec590, status=15 '\017') at ../hw/net/virtio-net.c:370 20 0x000055f800d6c4b2 in virtio_set_status (vdev=0x55f8044ec590, val=<optimized out>) at ../hw/virtio/virtio.c:1945 21 0x000055f800d11d9d in vm_state_notify (running=running@entry=false, state=state@entry=RUN_STATE_SHUTDOWN) at ../softmmu/runstate.c:333 22 0x000055f800d04e7a in do_vm_stop (state=state@entry=RUN_STATE_SHUTDOWN, send_stop=send_stop@entry=false) at ../softmmu/cpus.c:262
23 0x000055f800d04e99 in vm_shutdown () at ../softmmu/cpus.c:280 24 0x000055f800d126af in qemu_cleanup () at ../softmmu/runstate.c:81225 0x000055f800ad5b13 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at ../softmmu/main.c:51
From the trace pending read only occurs in stop path. The recursive virtio_net_set_status from virtio_net_handle_ctrl doesn't make sense to me. Not sure I got the reason why we need to handle pending host notification in userland vq, can you elaborate?
Thanks, -Siwei
Thanks7 0x0000558f52c6b89a in virtio_pci_set_guest_notifier (d=d@entry=0x558f568f0f60, n=n@entry=2, assign=assign@entry=true, with_irqfd=with_irqfd@entry=false) at ../hw/virtio/virtio-pci.c:974 8 0x0000558f52c6c0d8 in virtio_pci_set_guest_notifiers (d=0x558f568f0f60, nvqs=3, assign=true) at ../hw/virtio/virtio-pci.c:1019 9 0x0000558f52bf091d in vhost_net_start (dev=dev@entry=0x558f568f91f0, ncs=0x558f56937cd0, data_queue_pairs=data_queue_pairs@entry=1, cvq=cvq@entry=1) at ../hw/net/vhost_net.c:361 10 0x0000558f52d4e5e7 in virtio_net_set_status (status=<optimized out>, n=0x558f568f91f0) at ../hw/net/virtio-net.c:289 11 0x0000558f52d4e5e7 in virtio_net_set_status (vdev=0x558f568f91f0, status=15 '\017') at ../hw/net/virtio-net.c:370 12 0x0000558f52d6c4b2 in virtio_set_status (vdev=vdev@entry=0x558f568f91f0, val=val@entry=15 '\017') at ../hw/virtio/virtio.c:1945 13 0x0000558f52c69eff in virtio_pci_common_write (opaque=0x558f568f0f60, addr=<optimized out>, val=<optimized out>, size=<optimized out>) at ../hw/virtio/virtio-pci.c:1292 14 0x0000558f52d15d6e in memory_region_write_accessor (mr=0x558f568f19d0, addr=20, value=<optimized out>, size=1, shift=<optimized out>, mask=<optimized out>, attrs=...) at ../softmmu/memory.c:492 15 0x0000558f52d127de in access_with_adjusted_size (addr=addr@entry=20, value=value@entry=0x7f8cdbffe748, size=size@entry=1, access_size_min=<optimized out>, access_size_max=<optimized out>, access_fn=0x558f52d15cf0 <memory_region_write_accessor>, mr=0x558f568f19d0, attrs=...) at ../softmmu/memory.c:554 16 0x0000558f52d157ef in memory_region_dispatch_write (mr=mr@entry=0x558f568f19d0, addr=20, data=<optimized out>, op=<optimized out>, attrs=attrs@entry=...) at ../softmmu/memory.c:1504 17 0x0000558f52d078e7 in flatview_write_continue (fv=fv@entry=0x7f8accbc3b90, addr=addr@entry=103079215124, attrs=..., ptr=ptr@entry=0x7f8ce6300028, len=len@entry=1, addr1=<optimized out>, l=<optimized out>, mr=0x558f568f19d0) at ../../../include/qemu/host-utils.h:165 18 0x0000558f52d07b06 in flatview_write (fv=0x7f8accbc3b90, addr=103079215124, attrs=..., buf=0x7f8ce6300028, len=1) at ../softmmu/physmem.c:2822 19 0x0000558f52d0b36b in address_space_write (as=<optimized out>, addr=<optimized out>, attrs=..., buf=buf@entry=0x7f8ce6300028, len=<optimized out>) at ../softmmu/physmem.c:2914 20 0x0000558f52d0b3da in address_space_rw (as=<optimized out>, addr=<optimized out>, attrs=..., attrs@entry=..., buf=buf@entry=0x7f8ce6300028, len=<optimized out>, is_write=<optimized out>) at ../softmmu/physmem.c:2924 21 0x0000558f52dced09 in kvm_cpu_exec (cpu=cpu@entry=0x558f55c2da60) at ../accel/kvm/kvm-all.c:2903 22 0x0000558f52dcfabd in kvm_vcpu_thread_fn (arg=arg@entry=0x558f55c2da60) at ../accel/kvm/kvm-accel-ops.c:49 23 0x0000558f52f9f04a in qemu_thread_start (args=<optimized out>) at ../util/qemu-thread-posix.c:556 24 0x00007f8ce4392ea5 in start_thread () at /lib64/libpthread.so.0 25 0x00007f8ce40bb9fd in clone () at /lib64/libc.so.6 Fixes: 4023784 ("vhost-vdpa: multiqueue support") Cc: Jason Wang <jasowang@redhat.com> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com> --- hw/virtio/virtio-bus.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c index 0f69d1c..3159b58 100644 --- a/hw/virtio/virtio-bus.c +++ b/hw/virtio/virtio-bus.c @@ -311,7 +311,8 @@ void virtio_bus_cleanup_host_notifier(VirtioBusState *bus, int n) /* Test and clear notifier after disabling event, * in case poll callback didn't have time to run. */ - virtio_queue_host_notifier_read(notifier); + if (!vdev->disable_ioeventfd_handler) + virtio_queue_host_notifier_read(notifier); event_notifier_cleanup(notifier); } -- 1.8.3.1
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