Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.32 as permitted sender) client-ip=23.128.96.32;
Message-ID: <5c7920fc-7e15-dbd2-91e6-c6822500d9ec@linux.ibm.com>
Date:   Fri, 15 Sep 2023 10:04:12 -0400
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.13.0
Subject: Re: [PATCH 0/2] a couple of corrections to the IRQ enablement
 function
Content-Language: en-US
To:     Matthew Rosato <mjrosato@linux.ibm.com>,
        linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org
Cc:     jjherne@linux.ibm.com, pasic@linux.ibm.com,
        alex.williamson@redhat.com, borntraeger@linux.ibm.com,
        kwankhede@nvidia.com, frankja@linux.ibm.com,
        imbrenda@linux.ibm.com, david@redhat.com,
        Michael Mueller <mimu@linux.ibm.com>
References: <20230913130626.217665-1-akrowiak@linux.ibm.com>
 <83cab22d-71c3-2bbc-856f-6527479f10ec@linux.ibm.com>
From:   Tony Krowiak <akrowiak@linux.ibm.com>
In-Reply-To: <83cab22d-71c3-2bbc-856f-6527479f10ec@linux.ibm.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
Precedence: bulk


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(-)
>>
>