linux-kernel - Re: [PATCH v5 1/7] s390: ap: kvm: add PQAP interception for AQIC

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Date:   Fri, 15 Mar 2019 14:44:19 +0100
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>
Cc:     borntraeger@...ibm.com, alex.williamson@...hat.com,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, frankja@...ux.ibm.com, akrowiak@...ux.ibm.com,
        pasic@...ux.ibm.com, david@...hat.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, freude@...ux.ibm.com, mimu@...ux.ibm.com
Subject: Re: [PATCH v5 1/7] s390: ap: kvm: add PQAP interception for AQIC

On 15/03/2019 14:41, Cornelia Huck wrote:
> On Fri, 15 Mar 2019 14:26:34 +0100
> Pierre Morel <pmorel@...ux.ibm.com> wrote:
> 
>> Conclusion:  we must handle this in userland, it will have the benefit
>> to keep old behavior when there is no callback.
>> OLD QEMU will not see change as they will not set aqic facility
>> NEW QEMU will handle this correctly.
>>
>> In this case we also do not need to handle all other tests here but can
>> move it to the callback as Tony wanted.
>>
>> Would you agree with something simple like:
>>
>> static int handle_pqap(struct kvm_vcpu *vcpu)
>> {
>>           int ret = -EOPNOTSUPP;
>>
>>           /* Verify that the hook callback is registered and call it */
>>           if (pqap_hook)
>>                   if (try_module_get(pqap_hook->owner)) {
>>                           ret = pqap_hook->hook(vcpu);
>>                           module_put(pqap_hook->owner);
>>                   }
>>           return ret;
>> }
>>
>> All other tests in QEMU and in the callback.
> 
> With the hook checking for priv, fc, etc.? Yeah, might work.
> 
> But don't count on my feedback too much right now, better wait for
> others' comments :) I'll resume in April, if needed.
> 

OK, thanks

Pierre

-- 
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany