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

From: Christian Borntraeger
Date: Fri Feb 14 2020 - 02:44:06 EST

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In reply to: Eugenio Perez Martin: "Re: vhost changes (batched) in linux-next after 12/13 trigger random crashes in KVM guests after reboot"
Next in thread: Christian Borntraeger: "Re: vhost changes (batched) in linux-next after 12/13 trigger random crashes in KVM guests after reboot"
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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
> <borntraeger@xxxxxxxxxx> 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 PÃrez 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?= <eperezma@xxxxxxxxxx>
>>> 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)
>>> };
>>>
>>>
>>
>

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