Subject: Re: [PATCH v1 1/2] KVM: PPC: Book3S HV: Add support for H_RPT_INVALIDATE (nested case only)

From: Bharata B Rao <[email-masked]>
Date: Fri, 11 Dec 2020 16:03:36 +0530

On Mon, Oct 19, 2020 at 04:56:41PM +0530, Bharata B Rao wrote:
> Implements H_RPT_INVALIDATE hcall and supports only nested case
> currently.
> 
> A KVM capability KVM_CAP_RPT_INVALIDATE is added to indicate the
> support for this hcall.

As Paul mentioned in the thread, this hcall does both process scoped
invalidations and partition scoped invalidations for L2 guest.
I am adding KVM_CAP_RPT_INVALIDATE capability with only partition
scoped invalidations (nested case) implemented in the hcall as we
don't see the need for KVM to implement process scoped invalidation
function as KVM may never run with LPCR[GTSE]=0.

I am wondering if enabling the capability with only partial
implementation of the hcall is the correct thing to do. In future
if we ever want process scoped invalidations support in this hcall,
we may not be able to differentiate the availability of two functions
cleanly from QEMU.

So does it make sense to implement the process scoped invalidation
function also now itself even if it is not going to be used in
KVM?

Regards,
Bharata.