Re: [PATCH v1 5/9] hw/virtio: introduce virtio_device_should_start

[Christian Borntraeger <borntraeger@linux.ibm.com>]

Am 15.11.22 um 17:05 schrieb Alex Bennée:
> 
> Christian Borntraeger <borntraeger@linux.ibm.com> writes:
> 
>> Am 15.11.22 um 15:31 schrieb Alex Bennée:
>>> "Michael S. Tsirkin" <mst@redhat.com> writes:
>>>
>>>> On Mon, Nov 14, 2022 at 06:15:30PM +0100, Christian Borntraeger wrote:
>>>>>
>>>>>
>>>>> Am 14.11.22 um 18:10 schrieb Michael S. Tsirkin:
>>>>>> On Mon, Nov 14, 2022 at 05:55:09PM +0100, Christian Borntraeger wrote:
>>>>>>>
>>>>>>>
>>>>>>> Am 14.11.22 um 17:37 schrieb Michael S. Tsirkin:
>>>>>>>> On Mon, Nov 14, 2022 at 05:18:53PM +0100, Christian Borntraeger wrote:
>>>>>>>>> Am 08.11.22 um 10:23 schrieb Alex Bennée:
>>>>>>>>>> The previous fix to virtio_device_started revealed a problem in its
>>>>>>>>>> use by both the core and the device code. The core code should be able
>>>>>>>>>> to handle the device "starting" while the VM isn't running to handle
>>>>>>>>>> the restoration of migration state. To solve this dual use introduce a
>>>>>>>>>> new helper for use by the vhost-user backends who all use it to feed a
>>>>>>>>>> should_start variable.
>>>>>>>>>>
>>>>>>>>>> We can also pick up a change vhost_user_blk_set_status while we are at
>>>>>>>>>> it which follows the same pattern.
>>>>>>>>>>
>>>>>>>>>> Fixes: 9f6bcfd99f (hw/virtio: move vm_running check to virtio_device_started)
>>>>>>>>>> Fixes: 27ba7b027f (hw/virtio: add boilerplate for vhost-user-gpio device)
>>>>>>>>>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>>>>>>>>>> Cc: "Michael S. Tsirkin" <mst@redhat.com>
>>>>>>>>>
>>>>>>>>> Hmmm, is this
>>>>>>>>> commit 259d69c00b67c02a67f3bdbeeea71c2c0af76c35
>>>>>>>>> Author:     Alex Bennée <alex.bennee@linaro.org>
>>>>>>>>> AuthorDate: Mon Nov 7 12:14:07 2022 +0000
>>>>>>>>> Commit:     Michael S. Tsirkin <mst@redhat.com>
>>>>>>>>> CommitDate: Mon Nov 7 14:08:18 2022 -0500
>>>>>>>>>
>>>>>>>>>         hw/virtio: introduce virtio_device_should_start
>>>>>>>>>
>>>>>>>>> and older version?
>>>>>>>>
>>>>>>>> This is what got merged:
>>>>>>>> https://lore.kernel.org/r/20221107121407.1010913-1-alex.bennee%40linaro.org
>>>>>>>> This patch was sent after I merged the RFC.
>>>>>>>> I think the only difference is the commit log but I might be missing
>>>>>>>> something.
>>>>>>>>
>>>>>>>>> This does not seem to fix the regression that I have reported.
>>>>>>>>
>>>>>>>> This was applied on top of 9f6bcfd99f which IIUC does, right?
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>> QEMU master still fails for me for suspend/resume to disk:
>>>>>>>
>>>>>>> #0  0x000003ff8e3980a6 in __pthread_kill_implementation () at /lib64/libc.so.6
>>>>>>> #1  0x000003ff8e348580 in raise () at /lib64/libc.so.6
>>>>>>> #2  0x000003ff8e32b5c0 in abort () at /lib64/libc.so.6
>>>>>>> #3  0x000003ff8e3409da in __assert_fail_base () at /lib64/libc.so.6
>>>>>>> #4  0x000003ff8e340a4e in  () at /lib64/libc.so.6
>>>>>>> #5 0x000002aa1ffa8966 in vhost_vsock_common_pre_save
>>>>>>> (opaque=<optimized out>) at
>>>>>>> ../hw/virtio/vhost-vsock-common.c:203
>>>>>>> #6  0x000002aa1fe5e0ee in vmstate_save_state_v
>>>>>>>        (f=f@entry=0x2aa21bdc170, vmsd=0x2aa204ac5f0
>>>>>>> <vmstate_virtio_vhost_vsock>, opaque=0x2aa21bac9f8,
>>>>>>> vmdesc=vmdesc@entry=0x3fddc08eb30,
>>>>>>> version_id=version_id@entry=0) at ../migration/vmstate.c:329
>>>>>>> #7 0x000002aa1fe5ebf8 in vmstate_save_state
>>>>>>> (f=f@entry=0x2aa21bdc170, vmsd=<optimized out>,
>>>>>>> opaque=<optimized out>, vmdesc_id=vmdesc_id@entry=0x3fddc08eb30)
>>>>>>> at ../migration/vmstate.c:317
>>>>>>> #8 0x000002aa1fe75bd0 in vmstate_save (f=f@entry=0x2aa21bdc170,
>>>>>>> se=se@entry=0x2aa21bdbe90, vmdesc=vmdesc@entry=0x3fddc08eb30) at
>>>>>>> ../migration/savevm.c:908
>>>>>>> #9 0x000002aa1fe79584 in
>>>>>>> qemu_savevm_state_complete_precopy_non_iterable
>>>>>>> (f=f@entry=0x2aa21bdc170, in_postcopy=in_postcopy@entry=false,
>>>>>>> inactivate_disks=inactivate_disks@entry=true)
>>>>>>>        at ../migration/savevm.c:1393
>>>>>>> #10 0x000002aa1fe79a96 in qemu_savevm_state_complete_precopy
>>>>>>> (f=0x2aa21bdc170, iterable_only=iterable_only@entry=false,
>>>>>>> inactivate_disks=inactivate_disks@entry=true) at
>>>>>>> ../migration/savevm.c:1459
>>>>>>> #11 0x000002aa1fe6d6ee in migration_completion (s=0x2aa218ef600) at ../migration/migration.c:3314
>>>>>>> #12 migration_iteration_run (s=0x2aa218ef600) at ../migration/migration.c:3761
>>>>>>> #13 migration_thread (opaque=opaque@entry=0x2aa218ef600) at ../migration/migration.c:3989
>>>>>>> #14 0x000002aa201f0b8c in qemu_thread_start (args=<optimized out>) at ../util/qemu-thread-posix.c:505
>>>>>>> #15 0x000003ff8e396248 in start_thread () at /lib64/libc.so.6
>>>>>>> #16 0x000003ff8e41183e in thread_start () at /lib64/libc.so.6
>>>>>>>
>>>>>>> Michael, your previous branch did work if I recall correctly.
>>>>>>
>>>>>> That one was failing under github CI though (for reasons we didn't
>>>>>> really address, such as disconnect during stop causing a recursive
>>>>>> call to stop, but there you are).
>>>>> Even the double revert of everything?
>>>>
>>>> I don't remember at this point.
>>>>
>>>>> So how do we proceed now?
>>>>
>>>> I'm hopeful Alex will come up with a fix.
>>> I need to replicate the failing test for that. Which test is
>>> failing?
>>
>>
>> Pretty much the same as before. guest with vsock, managedsave and
>> restore.
> 
> If this isn't in our test suite I'm going to need exact steps.

Just get any libvirt guest, add
     <vsock model='virtio'>
       <cid auto='yes'/>
     </vsock>

to your libvirt xml. Start the guest (with the new xml).
Run virsh managedsave - qemu crashes. On x86 and s390.