Re: [Qemu-devel] [qemu-s390x] [PATCH v3 6/7] s390x/kvm: handle AP instruction interception

[David Hildenbrand]

On 26.03.2018 10:32, David Hildenbrand wrote:
> On 16.03.2018 00:24, Tony Krowiak wrote:
>> If the CPU model indicates that AP facility is installed on
>> the guest (i.e., -cpu xxxx,ap=on), then the expectation is that
>> the AP bus running in the guest will initialize; however, if the
>> AP instructions are not being interpreted by the firmware, then
>> they will be intercepted and routed back to QEMU for handling.
>> If a handler is not defined to process the intercepted instruciton,
>> then an operation exception will be injected into the
>> guest, in which case the AP bus will not initialize.
>>
>> There are two situations where AP instructions will not be
>> interpreted:
>>
>> 1. The guest is not configured with a vfio-ap device (i.e.,
>>    -device vfio-ap,sysfsdev=$path-to-mdev). The realize function for
>>    the vfio-ap device enables interpretive execution of AP
>>    instructions.
>>
>> 2. The guest is a second level guest but the first level guest has
>>    not enabled interpretive execution.
>>
>> This patch introduces AP instruction handlers to ensure the AP bus
>> module initializes on the guest when the AP facility is installed
>> on the guest but AP instructions are not being interpreted. The logic
>> incorporated is:
>>
>> * If the CPU model indicates AP instructions are
>>   installed
>>
>>   * Set the status response code for the instruction to indicate that
>>     the APQN contained in the instruction is not valid. This is
>>     a valid response because there will be no devices configured for
>>     the guest in any of the above scenarios.
>>
>> * Else return an error from the handler. This will result in an
>>   operation being injected into the guest and the AP bus will not
> 
> s/operation/operation exception/
> 
>>   initialize on the guest. That is commensurate with how things work
>>   today.
>>
>> Signed-off-by: Tony Krowiak <address@hidden>
>> ---
>>  hw/vfio/ap.c                 |   45 
>> ++++++++++++++++++++++++++++++++++++++++++
>>  include/hw/s390x/ap-device.h |    6 +++++
>>  target/s390x/kvm.c           |   14 +++++++++++++
>>  3 files changed, 65 insertions(+), 0 deletions(-)
>>
>> diff --git a/hw/vfio/ap.c b/hw/vfio/ap.c
>> index b397bb1..88e744d 100644
>> --- a/hw/vfio/ap.c
>> +++ b/hw/vfio/ap.c
>> @@ -148,6 +148,51 @@ static void vfio_ap_unrealize(DeviceState *dev, Error 
>> **errp)
>>      kvm_s390_set_interpret_ap(0);
>>  }
>>  
> 
> I think you are missing cpu_synchronize_state(CPU(cpu)) in all of these
> functions.
> 

No you don't. There is just a duplicate cpu_synchronize_state(CPU(cpu))
in kvm_sclp_service_call() which confused me.


-- 

Thanks,

David / dhildenb