Re: [PATCH 0/2] a couple of corrections to the IRQ enablement function

[Tony Krowiak <akrowiak@linux.ibm.com>]

On 9/13/23 14:13, Matthew Rosato wrote:
> On 9/13/23 9:06 AM, Tony Krowiak wrote:
>> This series corrects two issues related to enablement of interrupts in
>> response to interception of the PQAP(AQIC) command:
>>
>> 1. Returning a status response code 06 (Invalid address of AP-queue
>>     notification byte) when the call to register a guest ISC fails makes no
>>     sense.
>>     
>> 2. The pages containing the interrupt notification-indicator byte are not
>>     freed after a failure to register the guest ISC fails.
>>
> 
> Hi Tony,
> 
> 3. Since you're already making changes related to gisc registration, you might consider a 3rd patch that looks at the return code for kvm_s390_gisc_unregister and tags the unexpected error rc somehow.  This came up in a recent conversation I had with Michael, see this conversation towards the bottom:
> 
> https://lore.kernel.org/linux-s390/0ddf808c-e929-c975-1b39-5ebc1f2fab62@linux.ibm.com/

When we receive a non-zero return code from kvm_s390_gisc_register, we 
log a DBF warning message. We can do the same for a non-zero rc from 
kvm_s390_gisc_unregister.

> 
> 4. While looking at patch 1 I also had a question re: the AP_RESPONSE_OTHERWISE_CHANGED path in vfio_ap_irq_enable.  Here's a snippet of the current code:
> 
> 	case AP_RESPONSE_OTHERWISE_CHANGED:
> 		/* We could not modify IRQ settings: clear new configuration */
> 		vfio_unpin_pages(&q->matrix_mdev->vdev, nib, 1);
> 		kvm_s390_gisc_unregister(kvm, isc);
> 		break;
> 
> Is it safe to unpin the page before unregistering the gisc in this case?  Or shouldn't the unpin happen after we have unregistered the gisc / set the IAM?

I don't know the answer to the question, but it makes logical sense; so, 
I'll go ahead and create a third patch as you suggested.

> 
>> Anthony Krowiak (2):
>>    s390/vfio-ap: unpin pages on gisc registration failure
>>    s390/vfio-ap: set status response code to 06 on gisc registration
>>      failure
>>
>>   drivers/s390/crypto/vfio_ap_ops.c | 5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
>>
>