linux-kernel - Re: [PATCH 1/5] ACPI: NUMA: Add 'nohmat' option

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Date:   Wed, 18 Mar 2020 10:39:37 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Linux ACPI <linux-acpi@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/5] ACPI: NUMA: Add 'nohmat' option

On Wed, Mar 18, 2020 at 1:24 AM Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Wed, Mar 18, 2020 at 1:09 AM Dan Williams <dan.j.williams@...el.com> wrote:
> >
> > On Mon, Mar 2, 2020 at 2:36 PM Dan Williams <dan.j.williams@...el.com> wrote:
> > >
> > > Disable parsing of the HMAT for debug, to workaround broken platform
> > > instances, or cases where it is otherwise not wanted.
> >
> > Rafael, any heartburn with this change to the numa= option?
> >
> > ...as I look at this I realize I failed to also update
> > Documentation/x86/x86_64/boot-options.rst, will fix.
>
> Thanks!
>
> Apart from this just a minor nit below.
>
> > >
> > > Cc: x86@...nel.org
> > > Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> > > Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> > > Cc: Andy Lutomirski <luto@...nel.org>
> > > Cc: Peter Zijlstra <peterz@...radead.org>
> > > Cc: Thomas Gleixner <tglx@...utronix.de>
> > > Cc: Ingo Molnar <mingo@...hat.com>
> > > Cc: Borislav Petkov <bp@...en8.de>
> > > Cc: "H. Peter Anvin" <hpa@...or.com>
> > > Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> > > ---
> > >  arch/x86/mm/numa.c       |    4 ++++
> > >  drivers/acpi/numa/hmat.c |    3 ++-
> > >  include/acpi/acpi_numa.h |    1 +
> > >  3 files changed, 7 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> > > index 59ba008504dc..22de2e2610c1 100644
> > > --- a/arch/x86/mm/numa.c
> > > +++ b/arch/x86/mm/numa.c
> > > @@ -44,6 +44,10 @@ static __init int numa_setup(char *opt)
> > >  #ifdef CONFIG_ACPI_NUMA
> > >         if (!strncmp(opt, "noacpi", 6))
> > >                 acpi_numa = -1;
> > > +#ifdef CONFIG_ACPI_HMAT
> > > +       if (!strncmp(opt, "nohmat", 6))
> > > +               hmat_disable = 1;
> > > +#endif
>
> I wonder if IS_ENABLED() would work here?

I took a look. hmat_disable, acpi_numa, and numa_emu_cmdline() are in
other compilation units. I could wrap writing those variables with
helper functions, and change numa_emu_cmdline(), to compile away when
their respective configuration options are not present.

Should we do that in general to have a touch point to report "you
specified an option that is invalid for your current kernel
configuration"? I'm happy to do that as a follow-on if you think it's
worthwhile.