Re: [PATCH v3 0/4] Make PDX compression optional

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

On Tue, Aug 08, 2023 at 02:02:16PM +0100, Alejandro Vallejo wrote:
> Currently there's a CONFIG_HAS_PDX Kconfig option, but it's impossible to
> disable it because the whole codebase performs unconditional
> compression/decompression operations on addresses. This has the
> unfortunate side effect that systems without a need for compression still
> have to pay the performance impact of juggling bits on every pfn<->pdx
> conversion (this requires reading several global variables). This series
> attempts to:
> 
>   * Leave the state of pdx and pdx compression documented
>   * Factor out compression so it _can_ be removed through Kconfig
>   * Make it so compression is disabled on x86 and enabled on both Aarch32
>     and Aarch64 by default.
> 
> Series summary:
> 
> Patch 1 Moves hard-coded compression-related logic to helper functions
> Patch 2 Refactors all instances of regions being validated for pdx
>         compression conformance so it's done through a helper
> Patch 3 Non-functional reorder in order to simplify the patch 8 diff
> Patch 4 Adds new Kconfig option to compile out PDX compression and removes
>         the old CONFIG_HAS_PDX, as it was non removable
> 
> Already committed:
> 
> v1/patch 1 documents the current general understanding of the pdx concept and
>            pdx compression in particular
> v1/patch 3 Marks the pdx compression globals as ro_after_init
> v2/patch 1 Documents the differences between arm32 and arm64 directmaps
> 
> Alejandro Vallejo (4):
>   mm: Factor out the pdx compression logic in ma/va converters
>   mm/pdx: Standardize region validation wrt pdx compression
>   pdx: Reorder pdx.[ch]
>   pdx: Add CONFIG_PDX_COMPRESSION as a common Kconfig option

@Jan: Just making sure, are you generally ok with this series as-is?

Thanks,
Alejandro