[PATCH v6 00/26] KVM: arm64: Introduce pKVM hyp VM and vCPU state at EL2

[Oliver Upton]

On Fri, Nov 11, 2022 at 04:54:14PM +0000, Marc Zyngier wrote:
> On Thu, 10 Nov 2022 19:02:33 +0000,
> Will Deacon <will at kernel.org> wrote:
> > 
> > Hi all,
> > 
> > This is version six of the pKVM EL2 state series, extending the pKVM
> > hypervisor code so that it can dynamically instantiate and manage VM
> > data structures without the host being able to access them directly.
> > These structures consist of a hyp VM, a set of hyp vCPUs and the stage-2
> > page-table for the MMU. The pages used to hold the hypervisor structures
> > are returned to the host when the VM is destroyed.
> > 
> > Previous versions are archived at:
> > 
> >   Mega-patch: https://lore.kernel.org/kvmarm/20220519134204.5379-1-will@kernel.org/
> >   v2: https://lore.kernel.org/all/20220630135747.26983-1-will@kernel.org/
> >   v3: https://lore.kernel.org/kvmarm/20220914083500.5118-1-will@kernel.org/
> >   v4: https://lore.kernel.org/kvm/20221017115209.2099-1-will@kernel.org/
> >   v5: https://lore.kernel.org/r/20221020133827.5541-1-will@kernel.org
> > 
> > The changes since v5 include:
> > 
> >   * Fix teardown ordering so that the host 'kvm' structure remains pins
> >     while the memcache is being filled.
> > 
> >   * Fixed a kerneldoc typo.
> > 
> >   * Included a patch from Oliver to rework the 'pkvm_mem_transition'
> >     structure and it's handling of the completer address.
> > 
> >   * Tweaked some commit messages and added new R-b tags.
> > 
> > As before, the final patch is RFC since it illustrates a very naive use
> > of the new hypervisor structures and subsequent changes will improve on
> > this once we have the guest private memory story sorted out.
> > 
> > Oliver: I'm pretty sure we're going to need to revert your completer
> > address cleanup as soon as we have guest-host sharing. We want to keep
> > the 'pkvm_mem_transition' structure 'const', but we will only know the
> > host address (PA) after walking the guest stage-2 and so we're going to
> > want to track that separately. Anyway, I've included it here at the end
> > so Marc can decide what he wants to do!
> 
> Thanks, I guess... :-/
> 
> If this patch is going to be reverted, I'd rather not take it (without
> guest/host sharing, we don't have much of a hypervisor).

+1, I'm more than happy being told my patch doesn't work :)

Having said that, if there are parts of the design that I've whined
about that are intentional then please educate me. Some things haven't
been quite as obvious, but I know you folks have been working on this
feature for a while.

I probably need to give the full patch-bomb another read to get all the
context too.

--
Thanks,
Oliver