Re: [PATCH V3 00/10] fix migration of suspended runstate

[Steven Sistare]

On 8/24/2023 5:09 PM, Steven Sistare wrote:
> On 8/17/2023 2:23 PM, Peter Xu wrote:
>> On Mon, Aug 14, 2023 at 11:54:26AM -0700, Steve Sistare wrote:
>>> Migration of a guest in the suspended runstate is broken.  The incoming
>>> migration code automatically tries to wake the guest, which is wrong;
>>> the guest should end migration in the same runstate it started.  Further,
>>> for a restored snapshot, the automatic wakeup fails.  The runstate is
>>> RUNNING, but the guest is not.  See the commit messages for the details.
>>
>> Hi Steve,
>>
>> I drafted two small patches to show what I meant, on top of this series.
>> Before applying these two, one needs to revert patch 1 in this series.
>>
>> After applied, it should also pass all three new suspend tests.  We can
>> continue the discussion here based on the patches.
> 
> Your 2 patches look good.  I suggest we keep patch 1, and I squash patch 2
> into the other patches.
> 
> There is one more fix needed: on the sending side, if the state is suspended,
> then ticks must be disabled so the tick globals are updated before they are
> written to vmstate.  Otherwise, tick starts at 0 in the receiver when
> cpu_enable_ticks is called.
> 
> -------------------------------------------
> diff --git a/migration/migration.c b/migration/migration.c
[...]
> -------------------------------------------

This diff is just a rough draft.  I need to resume ticks if the migration
fails or is cancelled, and I am trying to push the logic into vm_stop,
vm_stop_force_state, and vm_start, and/or vm_prepare_start.

- Steve