Re: [PATCH v3 0/5] KVM: arm64: nv: Implement nested stage-2 reverse map

[Itaru Kitayama]

On Thu, May 28, 2026 at 11:19:34AM +0100, Marc Zyngier wrote:
> On Wed, 20 May 2026 08:31:12 +0100,
> Itaru Kitayama <itaru.kitayama@xxxxxxxxxxx> wrote:
> > 
> > Hi Wei Lin,
> > 
> > On Sun, May 10, 2026 at 03:53:33PM +0100, Wei-Lin Chang wrote:
> > > Hi,
> > > 
> > > This is v3 of optimizing the shadow s2 mmu unmapping during MMU
> > > notifiers.
> > > 
> > > Two new preparatory patches are added, one reduces a hole in kvm_s2_mmu
> > > and another refactors the code a bit during s2 faults. Other changes are
> > > listed below.
> > > 
> > > * Changes from v2 [1]:
> > > 
> > >   - Removed "polluted" teminology.
> > > 
> > >   - Use xa_{mk, to}_value() when storing and retriving values from maple
> > >     trees.
> > > 
> > >   - Avoid using the 63rd bit in maple tree values so that xa_{mk, to}_value()
> > >     does not lose us a bit.
> > > 
> > >   - Added reverse map removal during TLBI handling.
> > > 
> > >   - Other suggested refactorings.
> > > 
> > > Thanks!
> > 
> > With this series applied on the recent kvmarm/fixes (minor local modification), 
> > your v3 hello_nested runs fine on all three page granules; without this 16KB 
> > kernel can't handle stage 2 unmapping paths. I tested using the latest QEMU only 
> > so wonder how you're testing.
> 
> Can you clarify this statement?
> 
> Are you saying that 16kB S2 unmap do not work with upstream? That
> seems odd, as it would mean NV wouldn't work on Apple HW, which
> represents two thirds of my development boxes...

Yes, I built this morning's upstream kvmarm/fixes with 16KB granule fresh, and tested
Wei Lin's propsed KVM selftest, hello_nested on QEMU with the small buildroot
filesystem and saw the above i.e., the stage 2 unmapping paths never finish.

I thought it was due to the Ubuntu userspace I was using for testing,
but not sure now.

Thanks,
Itaru.

> 
> Thanks,
> 
> 	M.
> 
> -- 
> Without deviation from the norm, progress is not possible.