David Hildenbrand <da...@redhat.com> writes:
> On 16.11.2017 18:37, Alex Bennée wrote:
>>
>> David Hildenbrand <da...@redhat.com> writes:
>>
>>> Currently, single threaded TCG with > 1 VCPU gets stuck during IPL, when
>>> the bios tries to switch to the loaded kernel via DIAG 308.
>>>
>>> pause_all_vcpus()/resume_all_vcpus() should not be called from a VCPU.
>>>
>>> And there is also no need for it. run_on_cpu() will make sure that the
>>> CPUs exit KVM/TCG, where they get stopped. Once stopped, they will no
>>> longer run.
>>>
>>> Signed-off-by: David Hildenbrand <da...@redhat.com>
>>> ---
>>> target/s390x/diag.c | 4 ----
>>> 1 file changed, 4 deletions(-)
>>>
>>> diff --git a/target/s390x/diag.c b/target/s390x/diag.c
>>> index dbbb9e886f..52bc348808 100644
>>> --- a/target/s390x/diag.c
>>> +++ b/target/s390x/diag.c
>>> @@ -27,7 +27,6 @@ static int modified_clear_reset(S390CPU *cpu)
>>> S390CPUClass *scc = S390_CPU_GET_CLASS(cpu);
>>> CPUState *t;
>>>
>>> - pause_all_vcpus();
>>> cpu_synchronize_all_states();
>>> CPU_FOREACH(t) {
>>> run_on_cpu(t, s390_do_cpu_full_reset, RUN_ON_CPU_NULL);
>>
>> I think you also need to fix the run_on_cpu to be a async_run_on_cpu as
>> you would otherwise hang waiting for run_on_cpu to finish on a
>> single-threaded TCG run (as you are in the only vCPU context).
>
> No, it works just fine for single threaded TCG. run_on_cpu() can deal
> with single threaded TCG just fine. (otherwise e.g. SIGP code also
> wouldn't work)
>
> In do_run_on_cpu, the following code always directly triggers for single
> threaded tcg:
>
> if (qemu_cpu_is_self(cpu)) {
>
> func(cpu, data);
>
> return;
>
> }
Sorry ignore what I said, qemu_cpu_is_self tests the underlying thread
not the vCPU which they all share.
--
Alex Bennée
