Re: [PATCH 4/4] s390x/pci: add supported DT information to clp response

[Matthew Rosato <mjrosato@linux.ibm.com>]

On 12/3/21 4:33 AM, Pierre Morel wrote:
> 
> 
> On 12/2/21 17:41, Matthew Rosato wrote:
>> The DTSM is a mask that specifies which I/O Address Translation 
>> designation
>> types are supported.  A linux guest today does not look at this field but
> 
> Even Linux is the most used guest it is not the only one so may be not 
> mention Linux here.
> 

OK

>> could in the future; let's advertise what QEMU actually supports.
>>
>> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
>> ---
>>   hw/s390x/s390-pci-bus.c         | 1 +
>>   hw/s390x/s390-pci-vfio.c        | 1 +
>>   include/hw/s390x/s390-pci-bus.h | 1 +
>>   include/hw/s390x/s390-pci-clp.h | 3 ++-
>>   4 files changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
>> index 1b51a72838..01b58ebc70 100644
>> --- a/hw/s390x/s390-pci-bus.c
>> +++ b/hw/s390x/s390-pci-bus.c
>> @@ -782,6 +782,7 @@ static void s390_pci_init_default_group(void)
>>       resgrp->i = 128;
>>       resgrp->maxstbl = 128;
>>       resgrp->version = 0;
>> +    resgrp->dtsm = ZPCI_DTSM;
> 
> OK
> 
>>   }
>>   static void set_pbdev_info(S390PCIBusDevice *pbdev)
>> diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
>> index 2a153fa8c9..6f80a47e29 100644
>> --- a/hw/s390x/s390-pci-vfio.c
>> +++ b/hw/s390x/s390-pci-vfio.c
>> @@ -160,6 +160,7 @@ static void s390_pci_read_group(S390PCIBusDevice 
>> *pbdev,
>>           resgrp->i = cap->noi;
>>           resgrp->maxstbl = cap->maxstbl;
>>           resgrp->version = cap->version;
>> +        resgrp->dtsm = ZPCI_DTSM;
> 
> Is it safe for VFIO whith interpretation?
> Shouldn't we extend the capability and use the host DTSM in this case?

We will do exactly this when there is an interpretation series.

For the current intercept-based code, QEMU only supports DT 1 for 
passthrough regardless of what the host is supporting and rejects all 
else (see check in reg_ioat)