Re: [Qemu-devel] [qemu-s390x] [PATCH v1] s390x: refactor reset/reipl handling

[Christian Borntraeger]

On 06/21/2018 06:20 PM, Christian Borntraeger wrote:
> 
> 
> On 06/21/2018 06:15 PM, David Hildenbrand wrote:
>> On 21.06.2018 17:49, Christian Borntraeger wrote:
>>>
>>>
>>> On 04/24/2018 12:18 PM, David Hildenbrand wrote:
>>>> Calling pause_all_vcpus()/resume_all_vcpus() from a VCPU thread might
>>>> not be the best idea. As pause_all_vcpus() temporarily drops the qemu
>>>> mutex, two parallel calls to pause_all_vcpus() can be active at a time,
>>>> resulting in a deadlock. (either by two VCPUs or by the main thread and a
>>>> VCPU)
>>>>
>>>> Let's handle it via the main loop instead, as suggested by Paolo. If we
>>>> would have two parallel reset requests by two different VCPUs at the
>>>> same time, the last one would win.
>>>>
>>>> We use the existing ipl device to handle it. The nice side effect is
>>>> that we can get rid of reipl_requested.
>>>>
>>>> This change implies that all reset handling now goes via the common
>>>> path, so "no-reboot" handling is now active for all kinds of reboots.
>>>
>>> Ok, this breaks the s390 IPL process when -no-reboot  is specified.
>>> The bios does a diagnose 308 subcode 1 to jump to the final image while
>>> at the same time resetting all devices. This is now blocked with -no-reboot
>>> (although it is actually the boot)
>>>
>>>
>>> I have noticed that with virt-install on iso images since virt-install
>>> specifies -no-reboot.
>>>
>>> Something like this seems to help but it is not a nice solution.
>>>
>>> diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
>>> index 0d67349004..7b32698eaa 100644
>>> --- a/hw/s390x/ipl.c
>>> +++ b/hw/s390x/ipl.c
>>> @@ -534,8 +534,14 @@ void s390_ipl_reset_request(CPUState *cs, enum 
>>> s390_reset reset_type)
>>>               */
>>>              ipl->iplb_valid = s390_gen_initial_iplb(ipl);
>>>          }
>>> +        qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET);
>>> +    } else  if (reset_type == S390_RESET_MODIFIED_CLEAR ||
>>> +                reset_type == S390_RESET_LOAD_NORMAL) {
>>> +   /* ignore -no-reboot */
>>> +        qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET_FORCE);
>>> +    } else {
>>> +        qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET);
>>>      }
>>> -    qemu_system_reset_request(SHUTDOWN_CAUSE_GUEST_RESET);
>>>      /* as this is triggered by a CPU, make sure to exit the loop */
>>>      if (tcg_enabled()) {
>>>          cpu_loop_exit(cs);
>>> diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
>>> index e893f72f3b..e9b11fd6cb 100644
>>> --- a/include/sysemu/sysemu.h
>>> +++ b/include/sysemu/sysemu.h
>>> @@ -44,6 +44,9 @@ typedef enum ShutdownCause {
>>>                                       turns that into a shutdown */
>>>      SHUTDOWN_CAUSE_GUEST_PANIC,   /* Guest panicked, and command line turns
>>>                                       that into a shutdown */
>>> +    SHUTDOWN_CAUSE_GUEST_RESET_FORCE,/* Guest reset that should ignore 
>>> --no-reboot
>>> +                                     useful for the subsystem resets on 
>>> s390 done
>>> +                                     for kdump and kexec */
>>>      SHUTDOWN_CAUSE__MAX,
>>>  } ShutdownCause;
>>>  
>>> diff --git a/vl.c b/vl.c
>>> index b3426e03d0..18f379e833 100644
>>> --- a/vl.c
>>> +++ b/vl.c
>>> @@ -1674,7 +1674,9 @@ void qemu_system_guest_panicked(GuestPanicInformation 
>>> *info)
>>>  
>>>  void qemu_system_reset_request(ShutdownCause reason)
>>>  {
>>> -    if (no_reboot) {
>>> +    if (reason == SHUTDOWN_CAUSE_GUEST_RESET_FORCE) {
>>> +       reset_requested = SHUTDOWN_CAUSE_GUEST_RESET;
>>
>> As the value is not use anywhere, you can make this less ugly by not
>> setting it like this maybe
>>
>> if (reason != SHUTDOWN_CAUSE_GUEST_RESET_FORCE && no_reboot)
> 
> I also change the reason from SHUTDOWN_CAUSE_GUEST_RESET_FORCE back
> to  SHUTDOWN_CAUSE_GUEST_RESET. I think I have to, so that the handler do not 
> need
> to be modified. No?

Now I see you point. You say nobody uses the value?