Re: [PATCH v3 07/14] KVM: s390: interfaces to configure/deconfigure guest's AP matrix

[Tony Krowiak]

On 04/03/2018 07:07 AM, Cornelia Huck wrote:
> On Wed, 14 Mar 2018 14:25:47 -0400
> Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx> wrote:
>
> > Provides interfaces to assign AP adapters, usage domains
> > and control domains to a KVM guest.
> >
> > A KVM guest is started by executing the Start Interpretive Execution (SIE)
> > instruction. The SIE state description is a control block that contains the
> > state information for a KVM guest and is supplied as input to the SIE
> > instruction. The SIE state description has a satellite structure called the
> > Crypto Control Block (CRYCB). The CRYCB contains three bitmask fields
> > identifying the adapters, queues (domains) and control domains assigned to
> > the KVM guest:
> >
> > * The AP Adapter Mask (APM) field identifies the AP adapters assigned to
> >    the KVM guest
> >
> > * The AP Queue Mask (AQM) field identifies the AP queues assigned to
> >    the KVM guest. Each AP queue is connected to a usage domain within
> >    an AP adapter.
> >
> > * The AP Domain Mask (ADM) field identifies the control domains
> >    assigned to the KVM guest.
> >
> > Each adapter, queue (usage domain) and control domain are identified by
> > a number from 0 to 255. The bits in each mask, from most significant to
> > least significant bit, correspond to the numbers 0-255. When a bit is
> > set, the corresponding adapter, queue (usage domain) or control domain
> > is assigned to the KVM guest.
> >
> > This patch will set the bits in the APM, AQM and ADM fields of the
> > CRYCB referenced by the KVM guest's SIE state description. The process
> > used is:
> >
> > 1. Verify that the bits to be set do not exceed the maximum bit
> >     number for the given mask.
> >
> > 2. Verify that the APQNs that can be derived from the intersection
> >     of the bits set in the APM and AQM fields of the KVM guest's CRYCB
> >     are not assigned to any other KVM guest running on the same linux
> >     host.
> >
> > 3. Set the APM, AQM and ADM in the CRYCB according to the matrix
> >     configured for the mediated matrix device via its sysfs
> >     adapter, domain and control domain attribute files respectively.
> >
> > Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx>
> > ---
> >   arch/s390/include/asm/kvm-ap.h        |   36 +++++
> >   arch/s390/kvm/kvm-ap.c                |  268 +++++++++++++++++++++++++++++++++
> >   drivers/s390/crypto/vfio_ap_ops.c     |   19 +++
> >   drivers/s390/crypto/vfio_ap_private.h |    4 +
> >   4 files changed, 327 insertions(+), 0 deletions(-)
> >
> > diff --git a/arch/s390/kvm/kvm-ap.c b/arch/s390/kvm/kvm-ap.c
> > index a2c6ad2..eb365e2 100644
> > --- a/arch/s390/kvm/kvm-ap.c
> > +++ b/arch/s390/kvm/kvm-ap.c
> > @@ -8,9 +8,129 @@
> >   
> >   #include <asm/kvm-ap.h>
> >   #include <asm/ap.h>
> > +#include <linux/bitops.h>
> >   
> >   #include "kvm-s390.h"
> >   
> > +static inline void kvm_ap_clear_crycb_masks(struct kvm *kvm)
> > +{
> > +	int crycb_fmt = kvm->arch.crypto.crycbd & CRYCB_FORMAT_MASK;
> > +
> > +	if (crycb_fmt == CRYCB_FORMAT2)
> > +		memset(&kvm->arch.crypto.crycb->apcb1, 0,
> > +		       sizeof(kvm->arch.crypto.crycb->apcb1));
> > +	else
> > +		memset(&kvm->arch.crypto.crycb->apcb0, 0,
> > +		       sizeof(kvm->arch.crypto.crycb->apcb0));
> > +}
> Should that rather be a switch/case? If there's a CRYCB_FORMAT3 in the
> future, I'd think that it's more likely that it uses apcb1 and not
> apcb0. Can't comment further without the architecture, obviously.
Maybe we should just clear both structures without regard to the CRYCB 
format.
> (...)
>
> > +static void kvm_ap_set_crycb_masks(struct kvm *kvm,
> > +				   struct kvm_ap_matrix *matrix)
> > +{
> > +	unsigned long *apm = kvm_ap_get_crycb_apm(kvm);
> > +	unsigned long *aqm = kvm_ap_get_crycb_aqm(kvm);
> > +	unsigned long *adm = kvm_ap_get_crycb_adm(kvm);
> > +
> > +	kvm_ap_clear_crycb_masks(kvm);
> > +	memcpy(apm, matrix->apm, KVM_AP_MASK_BYTES(matrix->apm_max));
> > +	memcpy(aqm, matrix->aqm, KVM_AP_MASK_BYTES(matrix->aqm_max));
> > +
> > +	/*
> > +	 * Merge the AQM and ADM since the ADM is a superset of the
> > +	 * AQM by architectural convention.
> Is this 'architectural convention' in the sense of 'there's a statement
> in the architecture that it always is like that', or in the sense of
> 'all real-life systems are like that'?
> [From my sketchy memory, this convention makes sense but is not
> enshrined; but I might misremember.]
The documentation states it is an agreed upon convention.
> > +	 */
> > +	bitmap_or(adm, adm, aqm, matrix->adm_max);
> > +}