Messages in this thread | | | Subject | Re: [PATCH v5 11/13] KVM: s390: implement mediated device open callback | From | Pierre Morel <> | Date | Mon, 11 Jun 2018 11:23:27 +0200 |
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On 08/06/2018 23:59, Tony Krowiak wrote: > On 06/07/2018 01:15 PM, Pierre Morel wrote: >>
...snip...
>>>> >>>>> >>>>> Why maintain a list of kvm_ap_matrix structures if we don't have >>>>> to; it is stored >>>>> with the mediated matrix device which is passed in to all of the >>>>> vfio_ap driver >>>>> callbacks. >>>> >>>> Because using the vm_list which is a static in kvm makes you stick >>>> inside the kvm code. > > I understand your point here, but even if we did maintain a list of > kvm_ap_matrix structures, > we still need the kvm code to configure the guest's CRYCB and > eventually ECA.28. There is > also code in kvm-ap.c that is called from KVM.
The only code from kvm-ap which is called from KVM is temporary code waiting for Harald to offer the clean interface to AP instructions.
> The idea behind kvm-ap.c is that all code > related to configuration of AP structures in KVM is in this one spot.
This I understand, but the code can be in one spot inside VFIO_AP instead of inside KVM. Putting the code inside KVM induce dependencies between KVM and AP while the kvm/vfio interface allows to avoid this dependency.
The purpose of VFIO_AP is to handle the CRYCB, all get/clear/set crycb masks functions should be in VFIO AP.
If we use wrappers in KVM, since the CRYCB is an a SIE extension, it is legitimate, the KVM interface to the CRYCB should only handle bitmaps and be unaware of the vfio_ap internal structures.
Another concern, the kvm_ap_validate_queue_sharing() should not be inside KVM because it is a decision of current VFIO_AP driver to not share the queues between guest of level 2.
The Z architecture does not allow to share AP queues between guests of level 1 but we could re-engineer the AP bus and the ' VFIO AP to offer queue sharing for guest level 2.
This would be a new VFIO_AP driver (and an AP bus extension). We should not have to change KVM for this.
Regards,
Pierre
> >> >> >> >
-- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany
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