Re: [PATCH V6 05/14] migration: propagate suspended runstate

[Steven Sistare <steven.sistare@oracle.com>]

On 12/5/2023 11:50 AM, Peter Xu wrote:
> On Mon, Dec 04, 2023 at 05:23:57PM -0500, Steven Sistare wrote:
>> The V6 code does not pass a state to vm_start, and knowledge of vm_was_suspended
>> is confined to the global_state and cpus functions.  IMO this is a more modular
>> and robust solution, as multiple sites may call vm_start(), and the right thing
>> happens.  Look at patch 6.  The changes are minimal because vm_start "just works".
> 
> Oh I think I see what you meant.  Sounds good then.
> 
> Shall we hide that into vm_prepare_start()?  It seems three's still one
> more call sites that always pass in RUNNING (gdb_continue_partial).
> 
> If with above, vm_prepare_start() will go into either RUNNING, SUSPENDED,
> or an error.  It returns 0 only if RUNNING, -1 for all the rest.  Maybe we
> can already also touch up the retval of vm_prepare_start() to be a boolean,
> reflecting "whether vcpu needs to be started".

Yes, that is even nicer, thanks.

/**
 * Prepare for (re)starting the VM.
 * Returns 0 if the vCPUs should be restarted, -1 on an error condition,
 * and 1 otherwise.
 */
int vm_prepare_start(bool step_pending)
{
    int ret = vm_was_suspended ? 1 : 0;
    RunState state = vm_was_suspended ? RUN_STATE_SUSPENDED : RUN_STATE_RUNNING;
    ...
    vm_was_suspended = false;
    return ret;
}

void vm_start(void)
{
    if (!vm_prepare_start(false)) {
        resume_all_vcpus();
    }
}

- Steve