Re: [PATCH 16/22] x86/mm: introduce a per-CPU L3 table for the per-domain slot

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Aug 16, 2024 at 07:40:40PM +0100, Alejandro Vallejo wrote:
> On Fri Jul 26, 2024 at 4:22 PM BST, Roger Pau Monne wrote:
> > So far L4 slot 260 has always been per-domain, in other words: all vCPUs of 
> > a
> > domain share the same L3 entry.  Currently only 3 slots are used in that L3
> > table, which leaves plenty of room.
> >
> > Introduce a per-CPU L3 that's used the the domain has Address Space 
> > Isolation
> > enabled.  Such per-CPU L3 gets currently populated using the same L3 entries
> > present on the per-domain L3 (d->arch.perdomain_l3_pg).
> >
> > No functional change expected, as the per-CPU L3 is always a copy of the
> > contents of d->arch.perdomain_l3_pg.
> >
> > Note that all the per-domain L3 entries are populated at domain create, and
> > hence there's no need to sync the state of the per-CPU L3 as the domain 
> > won't
> > yet be running when the L3 is modified.
> >
> > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> 
> Still scratching my head with the details on this, but in general I'm utterly
> confused whenever I read per-CPU in the series because it's not obvious which
> CPU (p or v) I should be thinking about. A general change that would help a 
> lot
> is to replace every instance of per-CPU with per-vCPU or per-pCPU as needed.

per-CPU is always per-pCPU, as CPU without any prefix should always
refer to a physical CPU.  I think it's only recently that we have
started using pCPU vs vCPU, in the past it always was CPU vs vCPU.

I will attempt to be better at explicitly using pCPU instead of CPU in
the commit messages, sorry.

Thanks, Roger.