linux-kernel - Re: [RFC 00/19] KVM: s390/crypto/vfio: guest dedicated crypto adapters

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Date:   Tue, 5 Dec 2017 15:06:57 +0100
From:   Cornelia Huck <cohuck@...hat.com>
To:     Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
Cc:     Pierre Morel <pmorel@...ux.vnet.ibm.com>,
        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,
        alifm@...ux.vnet.ibm.com, mjrosato@...ux.vnet.ibm.com,
        qemu-s390x@...gnu.org, jjherne@...ux.vnet.ibm.com,
        thuth@...hat.com, pasic@...ux.vnet.ibm.com
Subject: Re: [RFC 00/19] KVM: s390/crypto/vfio: guest dedicated crypto
 adapters

On Mon, 27 Nov 2017 19:39:32 -0500
Tony Krowiak <akrowiak@...ux.vnet.ibm.com> wrote:

> On 11/22/2017 08:47 AM, Cornelia Huck wrote:
> > On Tue, 21 Nov 2017 11:08:01 -0500
> > Tony Krowiak <akrowiak@...ux.vnet.ibm.com> wrote:
> >
> >  
> >> I am not quite sure what you are asking, but I'll attempt to answer
> >> what I think you're asking. A new type of mediated matrix device
> >> will be introduced to configure a virtual matrix for a guest that
> >> provides the interfaces to map a virtual adapter/domain ID to one
> >> or more real adapter/domain IDs. If by virtualization facility,
> >> you are talking about the VFIO AP matrix driver, then yes,
> >> the driver will handle ioctl requests based on the type of the
> >> mediated matrix device through which the request was submitted:
> >>
> >> If the request is to configure the KVM guest's matrix:
> >>
> >> * If the mediated matrix device type is passthrough:
> >>     * Do validation of matrix
> >>     * Configure the APM, AQM and ADM in the KVM guest's CRYCB
> >>       according to the configuration specified via the mediated
> >>       device's sysfs attribute files.
> >> * If the mediated matrix device type is virtual:
> >>     * Do validation of matrix
> >>     * No need to configure CRYCB since all instructions will be
> >>       intercepted  
> > Ok, so we would have two distinct paths here...  
> It depends upon what you mean by two distinct paths. Configuring the
> mediated device would require a new mediated device type for virtualized
> AP matrices. The ioctl for configuring the KVM guest's CRYCB would
> require an additional check to determine whether the CRYCB need be
> configured or not.

Yes, the new type makes this distinct enough so that we can think about
this later.

> >  
> >> If the request is to execute an intercepted AP instruction:
> >>
> >> * If the mediated matrix device type is passthrough:
> >>     * Forward the instruction to the AP device and return the
> >>       result to QEMU.
> >>
> >> * If the mediated matrix device type is virtual:
> >>
> >>     * Retrieve all of the real APQNs mapped to the virtual
> >>       adapter and domain IDs configured in the mediated matrix
> >>       device's sysfs attribute files
> >>     * If there is more than one APQN mapping, then determine
> >>       which would be best to use - algorithm TBD
> >>     * Forward the instruction to the AP device and return the
> >>       result.  
> > ...and two distinct paths for most instructions here as well.  
> The driver would require additional ioctls to handle
> interception of all AP instructions for virtual matrices and additional
> code to remap virtual APQNs to real APQNs and determine which real APQN
> to which intercepted instructions should be forwarded.
> >  
> >> Of course, these are just preliminary ideas at this time.
> >> I've only prototyped the sysfs configuration interfaces. No
> >> back end prototyping has been undertaken yet. If the ideas do
> >> not pan out, however; I think virtualization can be introduced
> >> as an independent design.  
> > Yes, let's cross that bridge when we get to it.  
> That is the plan. Given Pierre's objections, I thought it might help
> to touch on this.

OK, so I admit that I lost track a bit. Are there any remaining issues
beyond the feature handling? Would it make sense to post a v2?