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

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Date:   Wed, 13 Sep 2023 14:13:36 -0400
From:   Matthew Rosato <mjrosato@...ux.ibm.com>
To:     Tony Krowiak <akrowiak@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     jjherne@...ux.ibm.com, pasic@...ux.ibm.com,
        alex.williamson@...hat.com, borntraeger@...ux.ibm.com,
        kwankhede@...dia.com, frankja@...ux.ibm.com,
        imbrenda@...ux.ibm.com, david@...hat.com,
        Michael Mueller <mimu@...ux.ibm.com>
Subject: Re: [PATCH 0/2] a couple of corrections to the IRQ enablement
 function

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/ 

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?

> 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(-)
>