[PATCH v6 00/16] x86/mtrr: fix handling with PAT but without MTRR

Juergen Gross
2023-05-02T12:09:55Z

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

Changes in V5
- addressed comments
- some other small fixes
- new patches 3, 8 and 15

Changes in V6:
- patch 1 replaces patches 1+2 of V5
- new patches 8+12
- addressed comments

Juergen Gross (16):
x86/mtrr: remove physical address size calculation
x86/mtrr: replace some constants with defines
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: have only one set_mtrr() variant
x86/mtrr: move 32-bit code from mtrr.c to legacy.c
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: add mtrr=debug command line option
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()
x86/mtrr: remove unused code

.../admin-guide/kernel-parameters.txt | 4 +
arch/x86/hyperv/ivm.c | 4 +
arch/x86/include/asm/mtrr.h | 43 +-
arch/x86/include/uapi/asm/mtrr.h | 6 +-
arch/x86/kernel/cpu/mtrr/Makefile | 2 +-
arch/x86/kernel/cpu/mtrr/amd.c | 2 +-
arch/x86/kernel/cpu/mtrr/centaur.c | 11 +-
arch/x86/kernel/cpu/mtrr/cleanup.c | 22 +-
arch/x86/kernel/cpu/mtrr/cyrix.c | 2 +-
arch/x86/kernel/cpu/mtrr/generic.c | 677 ++++++++++++------
arch/x86/kernel/cpu/mtrr/legacy.c | 90 +++
arch/x86/kernel/cpu/mtrr/mtrr.c | 195 ++---
arch/x86/kernel/cpu/mtrr/mtrr.h | 18 +-
arch/x86/kernel/setup.c | 2 +
arch/x86/mm/pgtable.c | 24 +-
arch/x86/xen/enlighten_pv.c | 52 ++
16 files changed, 721 insertions(+), 433 deletions(-)
create mode 100644 arch/x86/kernel/cpu/mtrr/legacy.c

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2.35.3