linux-kernel - Re: [PATCH v5 00/16] x86: make PAT and MTRR independent from each other

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Date:   Wed, 2 Nov 2022 19:04:56 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Juergen Gross <jgross@...e.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-pm@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        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 v5 00/16] x86: make PAT and MTRR independent from each
 other

On Wed, Nov 02, 2022 at 08:46:57AM +0100, 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:

One of the AMD test boxes here says with this:

...
[    0.863466] PCI: not using MMCONFIG
[    0.863475] PCI: Using configuration type 1 for base access
[    0.863478] PCI: Using configuration type 1 for extended access
[    0.866733] mtrr: your CPUs had inconsistent MTRRdefType settings
[    0.866737] mtrr: probably your BIOS does not setup all CPUs.
[    0.866740] mtrr: corrected configuration.
[    0.869350] kprobes: kprobe jump-optimization is enabled. All kprobes are optimized if possible.
...

Previous logs don't have it:

PCI: not using MMCONFIG
PCI: Using configuration type 1 for base access
PCI: Using configuration type 1 for extended access
kprobes: kprobe jump-optimization is enabled. All kprobes are optimized if possible.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette