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

[Christian Borntraeger]

adding qemu devel and add Daniel and Erik from libvirt to keep them in the loop. 

On 10/29/2017 12:11 PM, Cornelia Huck wrote:
> On Fri, 13 Oct 2017 13:38:45 -0400
> Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx> wrote:
> 
>> Tony Krowiak (19):
>>   KVM: s390: SIE considerations for AP Queue virtualization
>>   KVM: s390: refactor crypto initialization
>>   s390/zcrypt: new AP matrix bus
>>   s390/zcrypt: create an AP matrix device on the AP matrix bus
>>   s390/zcrypt: base implementation of AP matrix device driver
>>   s390/zcrypt: register matrix device with VFIO mediated device
>>     framework
>>   KVM: s390: introduce AP matrix configuration interface
>>   s390/zcrypt: support for assigning adapters to matrix mdev
>>   s390/zcrypt: validate adapter assignment
>>   s390/zcrypt: sysfs interfaces supporting AP domain assignment
>>   s390/zcrypt: validate domain assignment
>>   s390/zcrypt: sysfs support for control domain assignment
>>   s390/zcrypt: validate control domain assignment
>>   KVM: s390: Connect the AP mediated matrix device to KVM
>>   s390/zcrypt: introduce ioctl access to VFIO AP Matrix driver
>>   KVM: s390: interface to configure KVM guest's AP matrix
>>   KVM: s390: validate input to AP matrix config interface
>>   KVM: s390: New ioctl to configure KVM guest's AP matrix
>>   s390/facilities: enable AP facilities needed by guest
> 
> I'll try to summarize all of this in my own words, both to make sure I
> understand the design correctly and to give others a different view on
> this.
> 
> [I'm completely disregarding control domains here.]
> 
> On s390, we have cryptographic coprocessor cards, which are modeled on
> Linux as devices on the AP bus. There's also a concept called domains,
> which means an individual queue of a crypto device is basically a
> (card,domain) tuple. We model this something like the following
> (assuming we have access to cards 3 and 4 and domains 1 and 2):
> 
> AP -> card3 -> queue (3,1)
>             -> queue (3,2)
>    -> card4 -> queue (4,1)
>             -> queue (4,2)
> 
> (The AP bus is a bit different for backwards compat.)
> 
> If we want to virtualize this, we can use a feature provided by the
> hardware. We basically attach a satellite control block to our main
> hardware virtualization control block and the hardware takes care of
> (mostly) everything.
> 
> For this control block, we don't specify explicit tuples, but a list of
> cards and a list of domains. The guest will get access to the cross
> product.
> 
> Because of this, we need to take care that the lists provided to
> different guests don't overlap; i.e., we need to enforce sane
> configurations. Otherwise, one guest may get access to things like
> secret keys for another guest.
> 
> The idea of this patch set is to introduce a new device, the matrix
> device. This matrix device hangs off a different root and acts as the
> node where mdev devices hang off.
> 
> If you now want to give the tuples (4,1) and (4,2), you need to do the
> following:
> 
> - Unbind the (4,1) and (4,2) tuples from their ap bus driver.
> - Bind the (4,1) and (4,2) tuples to the ap matrix driver.
> - Create the mediated device.
> - Assign card 4 and domains 1 and 2.
> 
> QEMU will now simply consume the mediated device and things should work.
> 

This is probably the shortest possible summary I can imagine.
Tony can you double check if it matches your understanding as well?