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

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Message-Id: <20230502120931.20719-1-jgross@suse.com>
Date:   Tue,  2 May 2023 14:09:15 +0200
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-hyperv@...r.kernel.org, linux-doc@...r.kernel.org
Cc:     mikelley@...rosoft.com, Juergen Gross <jgross@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org, Jonathan Corbet <corbet@....net>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH v6 00/16] x86/mtrr: fix handling with PAT but without MTRR

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

-- 
2.35.3