Re: [PATCH v6 1/5] KVM: Implement dirty quota-based throttling of vcpus

[Sean Christopherson <seanjc@google.com>]

On Thu, Sep 15, 2022, Christian Borntraeger wrote:
> Am 15.09.22 um 15:21 schrieb Christian Borntraeger:
> > I am wondering if this will work on s390. On s390  we only call
> > mark_page_dirty_in_slot for the kvm_read/write functions but not
> > for those done by the guest on fault. We do account those lazily in
> > kvm_arch_sync_dirty_log (like x96 in the past).
> > 
> 
> I think we need to rework the page fault handling on s390 to actually make
> use of this. This has to happen anyway somewhen (as indicated by the guest
> enter/exit rework from Mark). Right now we handle KVM page faults directly
> in the normal system fault handler. It seems we need to make a side turn
> into KVM for page faults on guests in the long run.

s390's page table management came up in conversation at KVM Forum in the context
of a common MMU (or MMUs)[*].  If/when we get an MMU that supports multiple
architectures, that would be a perfect opportunity for s390 to switch.  I don't
know that it'll be feasible to make a common MMU support s390 from the get-go,
but at the very least we can keep y'all in the loop and not make it unnecessarily
difficult to support s390.

[*] https://kvmforum2022.sched.com/event/15jJk