Re: [PATCH v8 07/22] KVM: s390: refactor crypto initialization

[Tony Krowiak]

On 08/09/2018 01:58 AM, Janosch Frank wrote:
> On 08.08.2018 16:44, Tony Krowiak wrote:
> > From: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
> >
> > This patch refactors the code that initializes and sets up the
> > crypto configuration for a guest. The following changes are
> > implemented via this patch:
> >
> > 1. Prior to the introduction of AP device virtualization, it
> >     was not necessary to provide guest access to the CRYCB
> >     unless the MSA extension 3 (MSAX3) facility was installed
> >     on the host system. With the introduction of AP device
> >     virtualization, the CRYCB must be made accessible to the
> >     guest if the AP instructions are installed on the host
> >     and are to be provided to the guest.
> >
> > 2. Introduces a flag indicating AP instructions executed on
> >     the guest shall be interpreted by the firmware. It is
> >     initialized to indicate AP instructions are to be
> >     to be interpreted and is used to set the SIE bit for
> >     each vcpu during vcpu setup.
> >
> > Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
> > Reviewed-by: Halil Pasic <pasic@xxxxxxxxxxxxx>
> > Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> > Tested-by: Michael Mueller <mimu@xxxxxxxxxxxxx>
> > Tested-by: Farhan Ali <alifm@xxxxxxxxxxxxx>
> > Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> Acked-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
>
> > ---
> >   arch/s390/include/asm/kvm_host.h |    3 +
> >   arch/s390/include/uapi/asm/kvm.h |    1 +
> >   arch/s390/kvm/kvm-s390.c         |   86 ++++++++++++++++++++------------------
> >   3 files changed, 49 insertions(+), 41 deletions(-)
> >
> > diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> > index af39561..0c13f61 100644
> > --- a/arch/s390/include/asm/kvm_host.h
> > +++ b/arch/s390/include/asm/kvm_host.h
> > @@ -187,6 +187,7 @@ struct kvm_s390_sie_block {
> >   #define ECA_AIV		0x00200000
> >   #define ECA_VX		0x00020000
> >   #define ECA_PROTEXCI	0x00002000
> > +#define ECA_APIE	0x00000008
> >   #define ECA_SII		0x00000001
> >   	__u32	eca;			/* 0x004c */
> >   #define ICPT_INST	0x04
> > @@ -256,6 +257,7 @@ struct kvm_s390_sie_block {
> >   	__u8	reservede4[4];		/* 0x00e4 */
> >   	__u64	tecmc;			/* 0x00e8 */
> >   	__u8	reservedf0[12];		/* 0x00f0 */
> > +#define CRYCB_FORMAT_MASK 0x00000003
> >   #define CRYCB_FORMAT1 0x00000001
> >   #define CRYCB_FORMAT2 0x00000003
> >   	__u32	crycbd;			/* 0x00fc */
> > @@ -714,6 +716,7 @@ struct kvm_s390_crypto {
> >   	__u32 crycbd;
> >   	__u8 aes_kw;
> >   	__u8 dea_kw;
> > +	__u8 apie;
> In the last review I wanted a comment here to know what they do.

I'm not sure what the 'they' are that you reference here. I couldn't
find your review comment but I assume you are looking for a comment
explaining what the 'apie' field is used for. I am removing
the 'apie' field based on a review comment by David, so there is
no longer a need for a comment here, assuming that is what you
are referring to.

> >   static void kvm_s390_vcpu_crypto_setup(struct kvm_vcpu *vcpu)
> >   {
> > -	if (!test_kvm_facility(vcpu->kvm, 76))
> > +	/*
> > +	 * If neither the AP instructions nor the MSAX3 facility are installed
> > +	 * on the host, then there is no need for a CRYCB in SIE because the
> > +	 * they will not be installed on the guest either.
> the they

I'll fix this grammatical error.

> > +	 */
> > +	if (ap_instructions_available() && !test_facility(76))
> >   		return;
> I know you're not responsible for that one :) but 0 being the wanted
> value here is a bit counter-intuitive.

Based on another review comment by David, I've changed this to:

if (!test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_AP) &&
    !test_kvm_facility(vcpu->kvm, 76))


> >   
> > -	vcpu->arch.sie_block->ecb3 &= ~(ECB3_AES | ECB3_DEA);
> > +	vcpu->arch.sie_block->crycbd = vcpu->kvm->arch.crypto.crycbd;
> > +
> > +	vcpu->arch.sie_block->eca &= ~ECA_APIE;
> The scb is zero allocated, are the ECA and the ECB3s set somewhere
> in-between, or is that your way of making sure the controls are
> definitely gone for good?

It is a bit of defensive programming. There is a KVM_SET_DEVICE_ATTR
ioctl to set crypto attributes (KVM_S390_VM_CRYPTO) that ultimately
calls the kvm_s390_vm_set_crypto() function. You'll notice that at the
end of that function, there is a call to kvm_s390_vcpu_crypto_reset_all()
that calls the kvm_s390_vcpu_crypto_setup() for each vcpu, so it would
seem that there is the possiblility that there could be a need to
set ECB3 to a different value. At any rate, I see no good reason to
remove this.

> > +	if (vcpu->kvm->arch.crypto.apie &&
> > +	    test_kvm_cpu_feat(vcpu->kvm, KVM_S390_VM_CPU_FEAT_AP))
> > +		vcpu->arch.sie_block->eca |= ECA_APIE;
> >   
> > -	if (vcpu->kvm->arch.crypto.aes_kw)
> > -		vcpu->arch.sie_block->ecb3 |= ECB3_AES;
> > -	if (vcpu->kvm->arch.crypto.dea_kw)
> > -		vcpu->arch.sie_block->ecb3 |= ECB3_DEA;
> > +	/* If MSAX3 is installed on the guest, set up protected key support */
> > +	if (test_kvm_facility(vcpu->kvm, 76)) {
> > +		vcpu->arch.sie_block->ecb3 &= ~(ECB3_AES | ECB3_DEA);
> >   
> > -	vcpu->arch.sie_block->crycbd = vcpu->kvm->arch.crypto.crycbd;
> > +		if (vcpu->kvm->arch.crypto.aes_kw)
> > +			vcpu->arch.sie_block->ecb3 |= ECB3_AES;
> > +		if (vcpu->kvm->arch.crypto.dea_kw)
> > +			vcpu->arch.sie_block->ecb3 |= ECB3_DEA;
> > +	}
> >   }
> >   
> >   void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu)