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

Cornelia Huck
2019-02-15T09:26:49Z

On Thu, 14 Feb 2019 17:45:06 +0100
Pierre Morel <pmorel@linux.ibm.com> wrote:

> On 14/02/2019 16:54, Cornelia Huck wrote:
> > On Thu, 14 Feb 2019 14:51:02 +0100
> > Pierre Morel <pmorel@linux.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
>

> >> + *
> >> + * 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

I'd just add a note to the patch description that this patch only
handles PQAP/AQCI and that handling PQAP/TAPQ is something for a
follow-on patch.

>
> >
> >> + * 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.

Ok.

>
> > (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?

Maybe also mention that in the function description?