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Date: Thu, 25 Apr 2024 11:23:54 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Salil Mehta <salil.mehta@...wei.com>
CC: Marc Zyngier <maz@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Peter
Zijlstra <peterz@...radead.org>, "linux-pm@...r.kernel.org"
<linux-pm@...r.kernel.org>, "loongarch@...ts.linux.dev"
<loongarch@...ts.linux.dev>, "linux-acpi@...r.kernel.org"
<linux-acpi@...r.kernel.org>, "linux-arch@...r.kernel.org"
<linux-arch@...r.kernel.org>, "linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>, "kvmarm@...ts.linux.dev"
<kvmarm@...ts.linux.dev>, "x86@...nel.org" <x86@...nel.org>, Russell King
<linux@...linux.org.uk>, "Rafael J . Wysocki" <rafael@...nel.org>, "Miguel
Luis" <miguel.luis@...cle.com>, James Morse <james.morse@....com>,
Jean-Philippe Brucker <jean-philippe@...aro.org>, Catalin Marinas
<catalin.marinas@....com>, Will Deacon <will@...nel.org>, Linuxarm
<linuxarm@...wei.com>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov
<bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
"justin.he@....com" <justin.he@....com>, "jianyong.wu@....com"
<jianyong.wu@....com>
Subject: Re: [PATCH v7 11/16] irqchip/gic-v3: Add support for ACPI's
disabled but 'online capable' CPUs
On Wed, 24 Apr 2024 18:08:30 +0100
Jonathan Cameron <Jonathan.Cameron@...wei.com> wrote:
> On Wed, 24 Apr 2024 17:35:54 +0100
> Salil Mehta <salil.mehta@...wei.com> wrote:
>
> > > From: Marc Zyngier <maz@...nel.org>
> > > Sent: Wednesday, April 24, 2024 4:33 PM
> > > To: Jonathan Cameron <jonathan.cameron@...wei.com>
> > > Cc: Thomas Gleixner <tglx@...utronix.de>; Peter Zijlstra
> > > <peterz@...radead.org>; linux-pm@...r.kernel.org;
> > > loongarch@...ts.linux.dev; linux-acpi@...r.kernel.org; linux-
> > > arch@...r.kernel.org; linux-kernel@...r.kernel.org; linux-arm-
> > > kernel@...ts.infradead.org; kvmarm@...ts.linux.dev; x86@...nel.org;
> > > Russell King <linux@...linux.org.uk>; Rafael J . Wysocki
> > > <rafael@...nel.org>; Miguel Luis <miguel.luis@...cle.com>; James Morse
> > > <james.morse@....com>; Salil Mehta <salil.mehta@...wei.com>; Jean-
> > > Philippe Brucker <jean-philippe@...aro.org>; Catalin Marinas
> > > <catalin.marinas@....com>; Will Deacon <will@...nel.org>; Linuxarm
> > > <linuxarm@...wei.com>; Ingo Molnar <mingo@...hat.com>; Borislav
> > > Petkov <bp@...en8.de>; Dave Hansen <dave.hansen@...ux.intel.com>;
> > > justin.he@....com; jianyong.wu@....com
> > > Subject: Re: [PATCH v7 11/16] irqchip/gic-v3: Add support for ACPI's
> > > disabled but 'online capable' CPUs
> > >
> > > On Wed, 24 Apr 2024 13:54:38 +0100,
> > > Jonathan Cameron <Jonathan.Cameron@...wei.com> wrote:
> > > >
> > > > On Tue, 23 Apr 2024 13:01:21 +0100
> > > > Marc Zyngier <maz@...nel.org> wrote:
> > > >
> > > > > On Mon, 22 Apr 2024 11:40:20 +0100,
> > > > > Jonathan Cameron <Jonathan.Cameron@...wei.com> wrote:
> > > > > >
> > > > > > On Thu, 18 Apr 2024 14:54:07 +0100 Jonathan Cameron
> > > > > > <Jonathan.Cameron@...wei.com> wrote:
> > >
> > > [...]
> > >
> > > > > >
> > > > > > > + /*
> > > > > > > + * Capable but disabled CPUs can be brought online later. What about
> > > > > > > + * the redistributor? ACPI doesn't want to say!
> > > > > > > + * Virtual hotplug systems can use the MADT's "always-on" GICR entries.
> > > > > > > + * Otherwise, prevent such CPUs from being brought online.
> > > > > > > + */
> > > > > > > + if (!(gicc->flags & ACPI_MADT_ENABLED)) {
> > > > > > > + pr_warn_once("CPU %u's redistributor is inaccessible: this CPU can't be brought online\n", cpu);
> > > > > > > + set_cpu_present(cpu, false);
> > > > > > > + set_cpu_possible(cpu, false);
> >
> > (a digression) shouldn't we be clearing the enabled mask as well?
> >
> > set_cpu_enabled(cpu, false);
>
> FWIW I think not necessary. enabled is only set in register_cpu() and aim here is to
> never call that for CPUs in this state.
>
> Anyhow, I got distracted by the firmware bug I found whilst trying to test this but
> now have a test setup that hits this path (once deliberately broken), so will
> see what we can do about that doesn't have affect those masks.
This may be relevant with the context of Marc's email. Don't crop so much!
However I think we probably don't care. This is bios bug, if we miss report it such
that userspace thinks it can online something that work work, it probably doesn't
matter.
Jonathan
>
> Jonathan
>
>
> >
> >
> > Best regards
> > Salil
>
>
> _______________________________________________
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> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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