linux-kernel - Re: [PATCH v4 00/16] x86: make pat and mtrr independent from each other

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Date:   Wed, 19 Oct 2022 09:18:00 +0200
From:   Juergen Gross <jgross@...e.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-pm@...r.kernel.org
Cc:     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>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Pavel Machek <pavel@....cz>, Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v4 00/16] x86: make pat and mtrr independent from each
 other

Ping?

On 04.10.22 10:10, Juergen Gross wrote:
> Today PAT can't be used without MTRR being available, unless MTRR is at
> least configured via CONFIG_MTRR and the system is running as Xen PV
> guest. In this case PAT is automatically available via the hypervisor,
> but the PAT MSR can't be modified by the kernel and MTRR is disabled.
> 
> The same applies to a kernel built with no MTRR support: it won't
> allow to use the PAT MSR, even if there is no technical reason for
> that, other than setting up PAT on all cpus the same way (which is a
> requirement of the processor's cache management) is relying on some
> MTRR specific code.
> 
> Fix all of that by:
> 
> - moving the function needed by PAT from MTRR specific code one level
>    up
> - reworking the init sequences of MTRR and PAT to be more similar to
>    each other without calling PAT from MTRR code
> - removing the dependency of PAT on MTRR
> 
> While working on that I discovered two minor bugs in MTRR code, which
> are fixed, too.
> 
> There is some more cleanup done reducing code size.
> 
> Changes in V4:
> - new patches 10, 14, 15, 16
> - split up old patch 4 into 3 patches
> - addressed comments
> 
> Changes in V3:
> - replace patch 1 by just adding a comment
> 
> Changes in V2:
> - complete rework of the patches based on comments by Boris Petkov
> - added several patches to the series
> 
> Juergen Gross (16):
>    x86/mtrr: add comment for set_mtrr_state() serialization
>    x86/mtrr: remove unused cyrix_set_all() function
>    x86/mtrr: replace use_intel() with a local flag
>    x86/mtrr: rename prepare_set() and post_set()
>    x86/mtrr: split MTRR specific handling from cache dis/enabling
>    x86: move some code out of arch/x86/kernel/cpu/mtrr
>    x86/mtrr: split generic_set_all()
>    x86/mtrr: remove set_all callback from struct mtrr_ops
>    x86/mtrr: simplify mtrr_bp_init()
>    x86/mtrr: get rid of mtrr_enabled bool
>    x86/mtrr: let cache_aps_delayed_init replace mtrr_aps_delayed_init
>    x86/mtrr: add a stop_machine() handler calling only cache_cpu_init()
>    x86: decouple pat and mtrr handling
>    x86: switch cache_ap_init() to hotplug callback
>    x86: do MTRR/PAT setup on all secondary CPUs in parallel
>    x86/mtrr: simplify mtrr_ops initialization
> 
>   arch/x86/include/asm/cacheinfo.h   |  18 +++
>   arch/x86/include/asm/memtype.h     |   5 +-
>   arch/x86/include/asm/mtrr.h        |  13 +-
>   arch/x86/kernel/cpu/cacheinfo.c    | 168 ++++++++++++++++++++++++++
>   arch/x86/kernel/cpu/common.c       |   2 +-
>   arch/x86/kernel/cpu/mtrr/amd.c     |   8 +-
>   arch/x86/kernel/cpu/mtrr/centaur.c |   8 +-
>   arch/x86/kernel/cpu/mtrr/cyrix.c   |  42 +------
>   arch/x86/kernel/cpu/mtrr/generic.c | 127 +++-----------------
>   arch/x86/kernel/cpu/mtrr/mtrr.c    | 185 ++++-------------------------
>   arch/x86/kernel/cpu/mtrr/mtrr.h    |  20 ++--
>   arch/x86/kernel/setup.c            |  14 +--
>   arch/x86/kernel/smpboot.c          |   9 +-
>   arch/x86/mm/pat/memtype.c          | 127 ++++++--------------
>   arch/x86/power/cpu.c               |   3 +-
>   include/linux/cpuhotplug.h         |   1 +
>   16 files changed, 298 insertions(+), 452 deletions(-)
> 


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