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SubjectRE: [PATCH v7 11/16] irqchip/gic-v3: Add support for ACPI's disabled but 'online capable' CPUs
Date
>  From: Marc Zyngier <maz@kernel.org>
> Sent: Wednesday, April 24, 2024 4:33 PM
> To: Jonathan Cameron <jonathan.cameron@huawei.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>; Peter Zijlstra
> <peterz@infradead.org>; linux-pm@vger.kernel.org;
> loongarch@lists.linux.dev; linux-acpi@vger.kernel.org; linux-
> arch@vger.kernel.org; linux-kernel@vger.kernel.org; linux-arm-
> kernel@lists.infradead.org; kvmarm@lists.linux.dev; x86@kernel.org;
> Russell King <linux@armlinux.org.uk>; Rafael J . Wysocki
> <rafael@kernel.org>; Miguel Luis <miguel.luis@oracle.com>; James Morse
> <james.morse@arm.com>; Salil Mehta <salil.mehta@huawei.com>; Jean-
> Philippe Brucker <jean-philippe@linaro.org>; Catalin Marinas
> <catalin.marinas@arm.com>; Will Deacon <will@kernel.org>; Linuxarm
> <linuxarm@huawei.com>; Ingo Molnar <mingo@redhat.com>; Borislav
> Petkov <bp@alien8.de>; Dave Hansen <dave.hansen@linux.intel.com>;
> justin.he@arm.com; jianyong.wu@arm.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@huawei.com> wrote:
> >
> > On Tue, 23 Apr 2024 13:01:21 +0100
> > Marc Zyngier <maz@kernel.org> wrote:
> >
> > > On Mon, 22 Apr 2024 11:40:20 +0100,
> > > Jonathan Cameron <Jonathan.Cameron@Huawei.com> wrote:
> > > >
> > > > On Thu, 18 Apr 2024 14:54:07 +0100 Jonathan Cameron
> > > > <Jonathan.Cameron@huawei.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);


Best regards
Salil

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