[PATCH v4 00/12] x86/mtrr: fix handling with PAT but without MTRR

[Juergen Gross]

This series tries to fix the rather special case of PAT being available
without having MTRRs (either due to CONFIG_MTRR being not set, or
because the feature has been disabled e.g. by a hypervisor).

The main use cases are Xen PV guests and SEV-SNP guests running under
Hyper-V.

Instead of trying to work around all the issues by adding if statements
here and there, just try to use the complete available infrastructure
by setting up a read-only MTRR state when needed.

In the Xen PV case the current MTRR MSR values can be read from the
hypervisor, while for the SEV-SNP case all needed is to set the
default caching mode to "WB".

I have added more cleanup which has been discussed when looking into
the most recent failures.

Note that I couldn't test the Hyper-V related change (patch 3).

Running on bare metal and with Xen didn't show any problems with the
series applied.

It should be noted that patches 9+10 are replacing today's way to
lookup the MTRR cache type for a memory region from looking at the
MTRR register values to building a memory map with the cache types.
This should make the lookup much faster and much easier to understand.

Changes in V2:
- replaced former patches 1+2 with new patches 1-4, avoiding especially
  the rather hacky approach of V1, while making all the MTRR type
  conflict tests available for the Xen PV case
- updated patch 6 (was patch 4 in V1)

Changes in V3:
- dropped patch 5 of V2, as already applied
- split patch 1 of V2 into 2 patches
- new patches 6-10
- addressed comments

Changes in V4:
- addressed comments

Juergen Gross (12):
  x86/mtrr: split off physical address size calculation
  x86/mtrr: optimize mtrr_calc_physbits()
  x86/mtrr: support setting MTRR state for software defined MTRRs
  x86/hyperv: set MTRR state when running as SEV-SNP Hyper-V guest
  x86/xen: set MTRR state when running as Xen PV initial domain
  x86/mtrr: replace vendor tests in MTRR code
  x86/mtrr: allocate mtrr_value array dynamically
  x86/mtrr: add get_effective_type() service function
  x86/mtrr: construct a memory map with cache modes
  x86/mtrr: use new cache_map in mtrr_type_lookup()
  x86/mtrr: don't let mtrr_type_lookup() return MTRR_TYPE_INVALID
  x86/mm: only check uniform after calling mtrr_type_lookup()

 arch/x86/include/asm/mtrr.h        |  15 +-
 arch/x86/include/uapi/asm/mtrr.h   |   6 +-
 arch/x86/kernel/cpu/mshyperv.c     |   4 +
 arch/x86/kernel/cpu/mtrr/amd.c     |   2 +-
 arch/x86/kernel/cpu/mtrr/centaur.c |   2 +-
 arch/x86/kernel/cpu/mtrr/cleanup.c |   4 +-
 arch/x86/kernel/cpu/mtrr/cyrix.c   |   2 +-
 arch/x86/kernel/cpu/mtrr/generic.c | 492 ++++++++++++++++++-----------
 arch/x86/kernel/cpu/mtrr/mtrr.c    |  94 +++---
 arch/x86/kernel/cpu/mtrr/mtrr.h    |   7 +-
 arch/x86/kernel/setup.c            |   2 +
 arch/x86/mm/pgtable.c              |  24 +-
 arch/x86/xen/enlighten_pv.c        |  52 +++
 13 files changed, 454 insertions(+), 252 deletions(-)

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2.35.3