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

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Date:   Tue, 3 Apr 2018 15:38:11 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, borntraeger@...ibm.com,
        kwankhede@...dia.com, bjsdjshi@...ux.vnet.ibm.com,
        pbonzini@...hat.com, alex.williamson@...hat.com,
        pmorel@...ux.vnet.ibm.com, alifm@...ux.vnet.ibm.com,
        mjrosato@...ux.vnet.ibm.com, jjherne@...ux.vnet.ibm.com,
        thuth@...hat.com, pasic@...ux.vnet.ibm.com, berrange@...hat.com,
        fiuczy@...ux.vnet.ibm.com, buendgen@...ibm.com
Subject: Re: [PATCH v3 07/14] KVM: s390: interfaces to configure/deconfigure
 guest's AP matrix

On Tue, 3 Apr 2018 09:17:59 -0400
Tony Krowiak <akrowiak@...ux.vnet.ibm.com> wrote:

> On 04/03/2018 07:07 AM, Cornelia Huck wrote:
> > On Wed, 14 Mar 2018 14:25:47 -0400
> > Tony Krowiak <akrowiak@...ux.vnet.ibm.com> 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@...ux.vnet.ibm.com>
> >> ---
> >>   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.

Yes; but my concern applies to the other checks for CRYCB_FORMAT2 as
well (snipped).