Subject: Re: vhost changes (batched) in linux-next after 12/13 trigger random crashes in KVM guests after reboot

From: Christian Borntraeger <[email-masked]>
Date: Fri, 14 Feb 2020 08:43:53 +0100

On 14.02.20 08:40, Eugenio Perez Martin wrote:
> Hi.
> 
> Were the vhost and vhost_net modules loaded with dyndbg='+plt'? I miss
> all the others regular debug traces on that one.

I did 

 echo -n 'file drivers/vhost/vhost.c +plt' > control
and
echo -n 'file drivers/vhost/net.c +plt'  > control

but apparently it did not work...me hates dynamic debug.

> 
> Thanks!
> 
> On Fri, Feb 14, 2020 at 8:34 AM Christian Borntraeger
> <[email-masked]> wrote:
>>
>> I did
>> ping -c 20 -f ... ; reboot
>> twice
>>
>> The ping after the first reboot showed .......E
>>
>> this was on the host console
>>
>> [   55.951885] CPU: 34 PID: 1908 Comm: CPU 0/KVM Not tainted 5.5.0+ #21
>> [   55.951891] Hardware name: IBM 3906 M04 704 (LPAR)
>> [   55.951892] Call Trace:
>> [   55.951902]  [<0000001ede114132>] show_stack+0x8a/0xd0
>> [   55.951906]  [<0000001edeb0672a>] dump_stack+0x8a/0xb8
>> [   55.951915]  [<000003ff803736a6>] vhost_vring_ioctl+0x6fe/0x858 [vhost]
>> [   55.951919]  [<000003ff8042a608>] vhost_net_ioctl+0x510/0x570 [vhost_net]
>> [   55.951924]  [<0000001ede3c4dd8>] do_vfs_ioctl+0x430/0x6f8
>> [   55.951926]  [<0000001ede3c5124>] ksys_ioctl+0x84/0xb0
>> [   55.951927]  [<0000001ede3c51ba>] __s390x_sys_ioctl+0x2a/0x38
>> [   55.951931]  [<0000001edeb27f72>] system_call+0x2a6/0x2c8
>> [   55.951949] CPU: 34 PID: 1908 Comm: CPU 0/KVM Not tainted 5.5.0+ #21
>> [   55.951950] Hardware name: IBM 3906 M04 704 (LPAR)
>> [   55.951951] Call Trace:
>> [   55.951952]  [<0000001ede114132>] show_stack+0x8a/0xd0
>> [   55.951954]  [<0000001edeb0672a>] dump_stack+0x8a/0xb8
>> [   55.951956]  [<000003ff803736a6>] vhost_vring_ioctl+0x6fe/0x858 [vhost]
>> [   55.951958]  [<000003ff8042a608>] vhost_net_ioctl+0x510/0x570 [vhost_net]
>> [   55.951959]  [<0000001ede3c4dd8>] do_vfs_ioctl+0x430/0x6f8
>> [   55.951961]  [<0000001ede3c5124>] ksys_ioctl+0x84/0xb0
>> [   55.951962]  [<0000001ede3c51ba>] __s390x_sys_ioctl+0x2a/0x38
>> [   55.951964]  [<0000001edeb27f72>] system_call+0x2a6/0x2c8
>> [   55.951997] Guest moved vq 0000000063d896c6 used index from 44 to 0
>> [   56.609831] unexpected descriptor format for RX: out 0, in 0
>> [   86.540460] CPU: 6 PID: 1908 Comm: CPU 0/KVM Not tainted 5.5.0+ #21
>> [   86.540464] Hardware name: IBM 3906 M04 704 (LPAR)
>> [   86.540466] Call Trace:
>> [   86.540473]  [<0000001ede114132>] show_stack+0x8a/0xd0
>> [   86.540477]  [<0000001edeb0672a>] dump_stack+0x8a/0xb8
>> [   86.540486]  [<000003ff803736a6>] vhost_vring_ioctl+0x6fe/0x858 [vhost]
>> [   86.540490]  [<000003ff8042a608>] vhost_net_ioctl+0x510/0x570 [vhost_net]
>> [   86.540494]  [<0000001ede3c4dd8>] do_vfs_ioctl+0x430/0x6f8
>> [   86.540496]  [<0000001ede3c5124>] ksys_ioctl+0x84/0xb0
>> [   86.540498]  [<0000001ede3c51ba>] __s390x_sys_ioctl+0x2a/0x38
>> [   86.540501]  [<0000001edeb27f72>] system_call+0x2a6/0x2c8
>> [   86.540524] CPU: 6 PID: 1908 Comm: CPU 0/KVM Not tainted 5.5.0+ #21
>> [   86.540525] Hardware name: IBM 3906 M04 704 (LPAR)
>> [   86.540526] Call Trace:
>> [   86.540527]  [<0000001ede114132>] show_stack+0x8a/0xd0
>> [   86.540528]  [<0000001edeb0672a>] dump_stack+0x8a/0xb8
>> [   86.540531]  [<000003ff803736a6>] vhost_vring_ioctl+0x6fe/0x858 [vhost]
>> [   86.540532]  [<000003ff8042a608>] vhost_net_ioctl+0x510/0x570 [vhost_net]
>> [   86.540534]  [<0000001ede3c4dd8>] do_vfs_ioctl+0x430/0x6f8
>> [   86.540536]  [<0000001ede3c5124>] ksys_ioctl+0x84/0xb0
>> [   86.540537]  [<0000001ede3c51ba>] __s390x_sys_ioctl+0x2a/0x38
>> [   86.540538]  [<0000001edeb27f72>] system_call+0x2a6/0x2c8
>> [   86.540570] unexpected descriptor format for RX: out 0, in 0
>> [   86.540577] Unexpected header len for TX: 0 expected 0
>>
>>
>> On 14.02.20 08:06, Eugenio Pérez wrote:
>>> Hi Christian.
>>>
>>> Sorry, that was meant to be applied over previous debug patch.
>>>
>>> Here I inline the one meant to be applied over eccb852f1fe6bede630e2e4f1a121a81e34354ab.
>>>
>>> Thanks!
>>>
>>> From d978ace99e4844b49b794d768385db3d128a4cc0 Mon Sep 17 00:00:00 2001
>>> From: =?UTF-8?q?Eugenio=20P=C3=A9rez?= <[email-masked]>
>>> Date: Fri, 14 Feb 2020 08:02:26 +0100
>>> Subject: [PATCH] vhost: disable all features and trace last_avail_idx and
>>>  ioctl calls
>>>
>>> ---
>>>  drivers/vhost/net.c   | 20 +++++++++++++++++---
>>>  drivers/vhost/vhost.c | 25 +++++++++++++++++++++++--
>>>  drivers/vhost/vhost.h | 10 +++++-----
>>>  3 files changed, 45 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>>> index e158159671fa..e4d5f843f9c0 100644
>>> --- a/drivers/vhost/net.c
>>> +++ b/drivers/vhost/net.c
>>> @@ -1505,10 +1505,13 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
>>>
>>>       mutex_lock(&n->dev.mutex);
>>>       r = vhost_dev_check_owner(&n->dev);
>>> -     if (r)
>>> +     if (r) {
>>> +             pr_debug("vhost_dev_check_owner index=%u fd=%d rc r=%d", index, fd, r);
>>>               goto err;
>>> +     }
>>>
>>>       if (index >= VHOST_NET_VQ_MAX) {
>>> +             pr_debug("vhost_dev_check_owner index=%u fd=%d MAX=%d", index, fd, VHOST_NET_VQ_MAX);
>>>               r = -ENOBUFS;
>>>               goto err;
>>>       }
>>> @@ -1518,22 +1521,26 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
>>>
>>>       /* Verify that ring has been setup correctly. */
>>>       if (!vhost_vq_access_ok(vq)) {
>>> +             pr_debug("vhost_net_set_backend index=%u fd=%d !vhost_vq_access_ok", index, fd);
>>>               r = -EFAULT;
>>>               goto err_vq;
>>>       }
>>>       sock = get_socket(fd);
>>>       if (IS_ERR(sock)) {
>>>               r = PTR_ERR(sock);
>>> +             pr_debug("vhost_net_set_backend index=%u fd=%d get_socket err r=%d", index, fd, r);
>>>               goto err_vq;
>>>       }
>>>
>>>       /* start polling new socket */
>>>       oldsock = vq->private_data;
>>>       if (sock != oldsock) {
>>> +             pr_debug("sock=%p != oldsock=%p index=%u fd=%d vq=%p", sock, oldsock, index, fd, vq);
>>>               ubufs = vhost_net_ubuf_alloc(vq,
>>>                                            sock && vhost_sock_zcopy(sock));
>>>               if (IS_ERR(ubufs)) {
>>>                       r = PTR_ERR(ubufs);
>>> +                     pr_debug("ubufs index=%u fd=%d err r=%d vq=%p", index, fd, r, vq);
>>>                       goto err_ubufs;
>>>               }
>>>
>>> @@ -1541,11 +1548,15 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
>>>               vq->private_data = sock;
>>>               vhost_net_buf_unproduce(nvq);
>>>               r = vhost_vq_init_access(vq);
>>> -             if (r)
>>> +             if (r) {
>>> +                     pr_debug("init_access index=%u fd=%d r=%d vq=%p", index, fd, r, vq);
>>>                       goto err_used;
>>> +             }
>>>               r = vhost_net_enable_vq(n, vq);
>>> -             if (r)
>>> +             if (r) {
>>> +                     pr_debug("enable_vq index=%u fd=%d r=%d vq=%p", index, fd, r, vq);
>>>                       goto err_used;
>>> +             }
>>>               if (index == VHOST_NET_VQ_RX)
>>>                       nvq->rx_ring = get_tap_ptr_ring(fd);
>>>
>>> @@ -1559,6 +1570,8 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
>>>
>>>       mutex_unlock(&vq->mutex);
>>>
>>> +     pr_debug("sock=%p", sock);
>>> +
>>>       if (oldubufs) {
>>>               vhost_net_ubuf_put_wait_and_free(oldubufs);
>>>               mutex_lock(&vq->mutex);
>>> @@ -1710,6 +1723,7 @@ static long vhost_net_ioctl(struct file *f, unsigned int ioctl,
>>>
>>>       switch (ioctl) {
>>>       case VHOST_NET_SET_BACKEND:
>>> +             pr_debug("VHOST_NET_SET_BACKEND");
>>>               if (copy_from_user(&backend, argp, sizeof backend))
>>>                       return -EFAULT;
>>>               return vhost_net_set_backend(n, backend.index, backend.fd);
>>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>>> index b5a51b1f2e79..ec25ba32fe81 100644
>>> --- a/drivers/vhost/vhost.c
>>> +++ b/drivers/vhost/vhost.c
>>> @@ -1642,15 +1642,30 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
>>>                       r = -EINVAL;
>>>                       break;
>>>               }
>>> +
>>> +             if (vq->last_avail_idx || vq->avail_idx) {
>>> +                     pr_debug(
>>> +                             "strange VHOST_SET_VRING_BASE [vq=%p][s.index=%u][s.num=%u]",
>>> +                             vq, s.index, s.num);
>>> +                     dump_stack();
>>> +                     r = 0;
>>> +                     break;
>>> +             }
>>>               vq->last_avail_idx = s.num;
>>>               /* Forget the cached index value. */
>>>               vq->avail_idx = vq->last_avail_idx;
>>> +             pr_debug(
>>> +                     "VHOST_SET_VRING_BASE [vq=%p][vq->last_avail_idx=%u][vq->avail_idx=%u][s.index=%u][s.num=%u]",
>>> +                     vq, vq->last_avail_idx, vq->avail_idx, s.index, s.num);
>>>               break;
>>>       case VHOST_GET_VRING_BASE:
>>>               s.index = idx;
>>>               s.num = vq->last_avail_idx;
>>>               if (copy_to_user(argp, &s, sizeof s))
>>>                       r = -EFAULT;
>>> +             pr_debug(
>>> +                     "VHOST_GET_VRING_BASE [vq=%p][vq->last_avail_idx=%u][vq->avail_idx=%u][s.index=%u][s.num=%u]",
>>> +                     vq, vq->last_avail_idx, vq->avail_idx, s.index, s.num);
>>>               break;
>>>       case VHOST_SET_VRING_KICK:
>>>               if (copy_from_user(&f, argp, sizeof f)) {
>>> @@ -2239,8 +2254,8 @@ static int fetch_buf(struct vhost_virtqueue *vq)
>>>               vq->avail_idx = vhost16_to_cpu(vq, avail_idx);
>>>
>>>               if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
>>> -                     vq_err(vq, "Guest moved used index from %u to %u",
>>> -                             last_avail_idx, vq->avail_idx);
>>> +                     vq_err(vq, "Guest moved vq %p used index from %u to %u",
>>> +                             vq, last_avail_idx, vq->avail_idx);
>>>                       return -EFAULT;
>>>               }
>>>
>>> @@ -2316,6 +2331,9 @@ static int fetch_buf(struct vhost_virtqueue *vq)
>>>       BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
>>>
>>>       /* On success, increment avail index. */
>>> +     pr_debug(
>>> +             "[vq=%p][vq->last_avail_idx=%u][vq->avail_idx=%u][vq->ndescs=%d][vq->first_desc=%d]",
>>> +             vq, vq->last_avail_idx, vq->avail_idx, vq->ndescs, vq->first_desc);
>>>       vq->last_avail_idx++;
>>>
>>>       return 0;
>>> @@ -2432,6 +2450,9 @@ EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
>>>  /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
>>>  void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
>>>  {
>>> +     pr_debug(
>>> +             "DISCARD [vq=%p][vq->last_avail_idx=%u][vq->avail_idx=%u][n=%d]",
>>> +             vq, vq->last_avail_idx, vq->avail_idx, n);
>>>       vq->last_avail_idx -= n;
>>>  }
>>>  EXPORT_SYMBOL_GPL(vhost_discard_vq_desc);
>>> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
>>> index 661088ae6dc7..08f6d2ccb697 100644
>>> --- a/drivers/vhost/vhost.h
>>> +++ b/drivers/vhost/vhost.h
>>> @@ -250,11 +250,11 @@ int vhost_init_device_iotlb(struct vhost_dev *d, bool enabled);
>>>       } while (0)
>>>
>>>  enum {
>>> -     VHOST_FEATURES = (1ULL << VIRTIO_F_NOTIFY_ON_EMPTY) |
>>> -                      (1ULL << VIRTIO_RING_F_INDIRECT_DESC) |
>>> -                      (1ULL << VIRTIO_RING_F_EVENT_IDX) |
>>> -                      (1ULL << VHOST_F_LOG_ALL) |
>>> -                      (1ULL << VIRTIO_F_ANY_LAYOUT) |
>>> +     VHOST_FEATURES = /* (1ULL << VIRTIO_F_NOTIFY_ON_EMPTY) | */
>>> +                      /* (1ULL << VIRTIO_RING_F_INDIRECT_DESC) | */
>>> +                      /* (1ULL << VIRTIO_RING_F_EVENT_IDX) | */
>>> +                      /* (1ULL << VHOST_F_LOG_ALL) | */
>>> +                      /* (1ULL << VIRTIO_F_ANY_LAYOUT) | */
>>>                        (1ULL << VIRTIO_F_VERSION_1)
>>>  };
>>>
>>>
>>
>