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

[Michael S. Tsirkin]

On Tue, Nov 15, 2022 at 09:18:27AM +0100, Christian Borntraeger wrote:
> 
> Am 14.11.22 um 18:20 schrieb Michael S. Tsirkin:
> > 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.
> 
> 
> The initial fix changed to qemu/master does still work for me
> 
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index a973811cbfc6..fb3072838119 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -411,14 +411,14 @@ static inline bool virtio_device_started(VirtIODevice 
> *vdev, uint8_t status)
>   */
>  static inline bool virtio_device_should_start(VirtIODevice *vdev, uint8_t 
> status)
>  {
> -    if (vdev->use_started) {
> -        return vdev->started;
> -    }
> -
>      if (!vdev->vm_running) {
>          return false;
>      }
> +    if (vdev->use_started) {
> +        return vdev->started;
> +    }
> +
>      return status & VIRTIO_CONFIG_S_DRIVER_OK;
>  }

Triggers failure on gitlab unfortunately:

https://gitlab.com/mstredhat/qemu/-/jobs/3323768122

-- 
MST