Re: [PATCH v2 01/10] x86/mtrr: fix MTRR fixup on APs

[Juergen Gross]

On 22.08.22 10:28, Borislav Petkov wrote:
> On Mon, Aug 22, 2022 at 07:17:40AM +0200, Juergen Gross wrote:
> > And then there is mtrr_state_warn() in arch/x86/kernel/cpu/mtrr/generic.c
> > which has a comment saying:
> >
> > /* Some BIOS's are messed up and don't set all MTRRs the same! */
>
> That thing also says:
>
>          pr_info("mtrr: probably your BIOS does not setup all CPUs.\n");
>          pr_info("mtrr: corrected configuration.\n");
>
> because it'll go and force on all CPUs the MTRR state it read from the
> BSP in mtrr_bp_init->get_mtrr_state.
>
> > Yes, the chances are slim to hit such a box,
>
> Well, my workstation says:
>
> $ dmesg | grep -i mtrr
> [    0.391514] mtrr: your CPUs had inconsistent variable MTRR settings
> [    0.395199] mtrr: probably your BIOS does not setup all CPUs.
> [    0.399199] mtrr: corrected configuration.
>
> but that's the variable MTRRs.
>
> > but your reasoning suggests I should remove the related code?
>
> My reasoning says you should not do anything at all here - works as
> advertized. :-)

And what about the:

  pr_warn("mtrr: your CPUs had inconsistent MTRRdefType settings\n");

This is the case the patch would fix.


Juergen

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