Re: [Qemu-devel] [PATCH v1 for-2.12 2/2] s390x: load_psw() should only exchange the PSW for KVM

[David Hildenbrand]

On 09.04.2018 13:40, Christian Borntraeger wrote:
> 
> 
> On 04/09/2018 01:36 PM, David Hildenbrand wrote:
>> On 09.04.2018 13:35, Christian Borntraeger wrote:
>>>
>>>
>>> On 04/09/2018 01:30 PM, David Hildenbrand wrote:
>>>> Let's simplify it a bit. On some weird circumstances we would have tried
>>>> to recompute watchpoints when running under KVM.



>>>>
>>>> Signed-off-by: David Hildenbrand <address@hidden>
>>>> ---
>>>>  target/s390x/helper.c | 10 ++++++----
>>>>  1 file changed, 6 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/target/s390x/helper.c b/target/s390x/helper.c
>>>> index 615fa24ab9..e8548f340a 100644
>>>> --- a/target/s390x/helper.c
>>>> +++ b/target/s390x/helper.c
>>>> @@ -103,16 +103,18 @@ void load_psw(CPUS390XState *env, uint64_t mask, 
>>>> uint64_t addr)
>>>>
>>>>      env->psw.addr = addr;
>>>>      env->psw.mask = mask;
>>>> -    if (tcg_enabled()) {
>>>> -        env->cc_op = (mask >> 44) & 3;
>>>> +
>>>> +    /* KVM will handle all WAITs and trigger a WAIT exit on disabled_wait 
>>>> */
>>>> +    if (!tcg_enabled()) {
>>>> +        return;
>>>>      }
>>>> +    env->cc_op = (mask >> 44) & 3;
>>>
>>> Do we have any call path were KVM could call load_psw?
>>
>> do_restart_interrupt()
>>
>> SIGP while the target CPU is stopped.
> 
> makes sense. Can you add that to the patch description? that makes it easier 
> to understand
> what can really go wrong without this patch.

Sure!

Conny, when (and if ;) ) picking this up, can you change the description to

"Let's simplify it a bit. On some weird circumstances we would have
tried to recompute watchpoints when running under KVM. load_psw() is
called from do_restart_interrupt() during a SIGP RESTART if the target
CPU is STOPPED. Let's touch watchpoints only in the TCG case - where
they are used for PER emulation."


-- 

Thanks,

David / dhildenb