[v2,0/5] Make PDX compression optional

Message

Alejandro Vallejo July 28, 2023, 7:58 a.m. UTC

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 makes a clarification in ARM code to explain some discrepancies
        between the concept of "directmap" in arm32 and arm64 relevant to
        this series (i.e: why this series doesn't touch arm32 in directmap
        accesses).
Patch 2 Moves hard-coded compression-related logic to helper functions
Patch 3 Refactors all instances of regions being validated for pdx
        compression conformance so it's done through a helper
Patch 4 Non-functional reorder in order to simplify the patch 8 diff
Patch 5 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

Alejandro Vallejo (5):
  arm/mm: Document the differences between arm32 and arm64 directmaps
  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_HAS_PDX_COMPRESSION as a common Kconfig option

 xen/arch/arm/Kconfig                   |   1 -
 xen/arch/arm/include/asm/mm.h          |  29 +++++-
 xen/arch/x86/Kconfig                   |   1 -
 xen/arch/x86/domain.c                  |  19 ++--
 xen/arch/x86/include/asm/x86_64/page.h |  28 +++---
 xen/arch/x86/x86_64/mm.c               |   7 +-
 xen/common/Kconfig                     |  13 ++-
 xen/common/Makefile                    |   2 +-
 xen/common/efi/boot.c                  |  13 ++-
 xen/common/pdx.c                       |  75 +++++++++------
 xen/include/xen/pdx.h                  | 126 +++++++++++++++++++------
 11 files changed, 218 insertions(+), 96 deletions(-)