Re: [PATCH v5 7/9] s390x/pci: enable adapter event notification for interpreted devices

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

On 4/22/22 5:39 AM, Pierre Morel wrote:
> 
> 
> On 4/4/22 20:17, Matthew Rosato wrote:
>> Use the associated kvm ioctl operation to enable adapter event 
>> notification
>> and forwarding for devices when requested.  This feature will be set up
>> with or without firmware assist based upon the 'forwarding_assist' 
>> setting.
>>
>> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
>> ---
>>   hw/s390x/s390-pci-bus.c         | 20 ++++++++++++++---
>>   hw/s390x/s390-pci-inst.c        | 40 +++++++++++++++++++++++++++++++--
>>   hw/s390x/s390-pci-kvm.c         | 30 +++++++++++++++++++++++++
>>   include/hw/s390x/s390-pci-bus.h |  1 +
>>   include/hw/s390x/s390-pci-kvm.h | 14 ++++++++++++
>>   5 files changed, 100 insertions(+), 5 deletions(-)
>>
>> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
>> index 9c02d31250..47918d2ce9 100644
>> --- a/hw/s390x/s390-pci-bus.c
>> +++ b/hw/s390x/s390-pci-bus.c
>> @@ -190,7 +190,10 @@ void s390_pci_sclp_deconfigure(SCCB *sccb)
>>           rc = SCLP_RC_NO_ACTION_REQUIRED;
>>           break;
>>       default:
>> -        if (pbdev->summary_ind) {
>> +        if (pbdev->interp && (pbdev->fh & FH_MASK_ENABLE)) {
>> +            /* Interpreted devices were using interrupt forwarding */
>> +            s390_pci_kvm_aif_disable(pbdev);
> 
> Same remark as for the kernel part.
> The VFIO device is already initialized and the action is on this device, 
> Shouldn't we use the VFIO device interface instead of the KVM interface?
> 

I don't necessarily disagree, but in v3 of the kernel series I was told 
not to use VFIO ioctls to accomplish tasks that are unique to KVM (e.g. 
AEN interpretation) and to instead use a KVM ioctl.

VFIO_DEVICE_SET_IRQS won't work as-is for reasons described in the 
kernel series (e.g. we don't see any of the config space notifiers 
because of instruction interpretation) -- as far as I can figure we 
could add our own s390 code to QEMU to issue VFIO_DEVICE_SET_IRQS 
directly for an interpreted device, but I think would also need 
s390-specific changes to VFIO_DEVICE_SET_IRQS accommodate this (e.g. 
maybe something like a VFIO_IRQ_SET_DATA_S390AEN where we can then 
specify the aen information in vfio_irq_set.data -- or something else I 
haven't though of yet) -- I can try to look at this some more and see if 
I get a good idea.