[PATCH v7 11/16] irqchip/gic-v3: Add support for ACPI's disabled but 'online capable' CPUs

[Salil Mehta]

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