linux-kernel - Re: [PATCH v3 2/9] s390: ap: kvm: setting a hook for PQAP instructions

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Message-Id: <2609f072-ab16-429e-8aba-e1af20757c25@linux.ibm.com>
Date:   Thu, 14 Feb 2019 17:45:06 +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 v3 2/9] s390: ap: kvm: setting a hook for PQAP
 instructions

On 14/02/2019 16:54, Cornelia Huck wrote:
> On Thu, 14 Feb 2019 14:51:02 +0100
> Pierre Morel <pmorel@...ux.ibm.com> wrote:
> 
>> This patch adds interception code for the PQAP instructions,
>> and a callback inside the KVM arch structure for s390.
>>
>> If a VFIO-AP drivers needs to intercept PQAP/AQIC or PQAP/TAPQ
> 
> s/drivers/driver/

thanks. OK

> 

...

>>   #include "kvm-s390.h"
>>   #include "trace.h"
>> @@ -592,6 +593,53 @@ static int handle_io_inst(struct kvm_vcpu *vcpu)
>>   	}
>>   }
>>   
>> +/*
>> + * handle_pqap: Handling pqap interception
>> + * @vcpu: the vcpu having issue the pqap instruction
> 
> s/issue/issued/

OK. thanks.

> 
>> + *
>> + * This callback only handles PQAP/AQIC instruction and
> 
> Here you only talk about PQAP/AQIC, what about PQAP/TAPQ mentioned in
> the patch description?

I can add "for now" or "in this patch" or suppress the reference to 
PAPQ/TAPQ

> 
>> + * calls a dedicated callback for this instruction if
>> + * a driver did register one in the CRYPTO satellite of the
>> + * SIE block.
>> + *
>> + * Do not change the behavior if, return -EOPNOTSUPP if:
>> + * - the hook is not used do not change the behavior.
> 
> The hook is not used? Or not set?

I think "is not set" is better.

> (I don't think you need to repeat "do
> not change the behavior".)

OK

> 
>> + * - AP instructions are not available or not available to the guest
>> + * - the instruction is not PQAP with function code indicating
>> + *   AQIC do not change the previous behavior.
>> + *
>> + * For PQAP/AQIC instruction, verify privilege and specifications
>> + *
>> + * return the value returned by the callback.
>> + */
>> +static int handle_pqap(struct kvm_vcpu *vcpu)
>> +{
>> +	uint8_t fc;
>> +
>> +	/* Verify that the hook callback is registered */
>> +	if (!vcpu->kvm->arch.crypto.pqap_hook)
>> +		return -EOPNOTSUPP;
>> +	/* Verify that the AP instruction are available */
>> +	if (!ap_instructions_available())
>> +		return -EOPNOTSUPP;
>> +	/* Verify that the guest is allowed to use AP instructions */
>> +	if (!(vcpu->arch.sie_block->eca & ECA_APIE))
>> +		return -EOPNOTSUPP;
>> +	/* Verify that the function code is AQIC */
>> +	fc = vcpu->run->s.regs.gprs[0] >> 24;
>> +	if (fc != 0x03)
>> +		return -EOPNOTSUPP;
>> +
>> +	/* PQAP instructions are allowed for guest kernel only */
>> +	if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PSTATE)
>> +		return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
>> +	/* AQIC instruction is allowed only if facility 65 is available */
>> +	if (!test_kvm_facility(vcpu->kvm, 65))
>> +		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
>> +	/* All right, call the callback */
>> +	return vcpu->kvm->arch.crypto.pqap_hook(vcpu);
> 
> Can that callback also return -EOPNOTSUPP to order to drop to user
> space?

Yes.
Why not?

> 
>> +}
>> +
>>   static int handle_stfl(struct kvm_vcpu *vcpu)
>>   {
>>   	int rc;
>> @@ -878,6 +926,8 @@ int kvm_s390_handle_b2(struct kvm_vcpu *vcpu)
>>   		return handle_sthyi(vcpu);
>>   	case 0x7d:
>>   		return handle_stsi(vcpu);
>> +	case 0xaf:
>> +		return handle_pqap(vcpu);
>>   	case 0xb1:
>>   		return handle_stfl(vcpu);
>>   	case 0xb2:
> 


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