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

[Pierre Morel]

On 14/02/2019 16:54, Cornelia Huck wrote:
> On Thu, 14 Feb 2019 14:51:02 +0100
> Pierre Morel <pmorel@xxxxxxxxxxxxx> 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 BÃblingen - Germany