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

["Alejandro Vallejo" <alejandro.vallejo@cloud.com>]

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@citrix.com>

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.

Cheers,
Alejandro