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From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	Russell King <rmk+kernel@armlinux.org.uk>,
	 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,
	 linux-riscv@lists.infradead.org, kvmarm@lists.linux.dev,
	x86@kernel.org,  acpica-devel@lists.linuxfoundation.org,
	linux-csky@vger.kernel.org,  linux-doc@vger.kernel.org,
	linux-ia64@vger.kernel.org,  linux-parisc@vger.kernel.org,
	Salil Mehta <salil.mehta@huawei.com>,
	 Jean-Philippe Brucker <jean-philippe@linaro.org>,
	jianyong.wu@arm.com, justin.he@arm.com,
	 James Morse <james.morse@arm.com>
Subject: Re: [PATCH RFC v4 02/15] ACPI: processor: Register all CPUs from acpi_processor_get_info()
Date: Wed, 10 Apr 2024 15:28:18 +0200	[thread overview]
Message-ID: <CAJZ5v0ggD042sfz3jDXQVDUxQZu_AWaF2ox-Me8CvFeRB8nczw@mail.gmail.com> (raw)
In-Reply-To: <20240410134318.0000193c@huawei.com>

On Wed, Apr 10, 2024 at 2:43 PM Jonathan Cameron
<Jonathan.Cameron@huawei.com> wrote:
>
> > >
> > > > diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> > > > index 47de0f140ba6..13d052bf13f4 100644
> > > > --- a/drivers/base/cpu.c
> > > > +++ b/drivers/base/cpu.c
> > > > @@ -553,7 +553,11 @@ static void __init cpu_dev_register_generic(void)
> > > >  {
> > > >         int i, ret;
> > > >
> > > > -       if (!IS_ENABLED(CONFIG_GENERIC_CPU_DEVICES))
> > > > +       /*
> > > > +        * When ACPI is enabled, CPUs are registered via
> > > > +        * acpi_processor_get_info().
> > > > +        */
> > > > +       if (!IS_ENABLED(CONFIG_GENERIC_CPU_DEVICES) || !acpi_disabled)
> > > >                 return;
> > >
> > > Honestly, this looks like a quick hack to me and it absolutely
> > > requires an ACK from the x86 maintainers to go anywhere.
> > Will address this separately.
> >
>
> So do people prefer this hack, or something along lines of the following?
>
> static int __init cpu_dev_register_generic(void)
> {
>         int i, ret = 0;
>
>         for_each_online_cpu(i) {
>                 if (!get_cpu_device(i)) {
>                         ret = arch_register_cpu(i);
>                         if (ret)
>                                 pr_warn("register_cpu %d failed (%d)\n", i, ret);
>                 }
>         }
>         //Probably just eat the error.
>         return 0;
> }
> subsys_initcall_sync(cpu_dev_register_generic);

I would prefer something like the above.

I actually thought that arch_register_cpu() might return something
like -EPROBE_DEFER when it cannot determine whether or not the CPU is
really available.

Then, the ACPI processor enumeration path may take care of registering
CPU that have not been registered so far and in the more-or-less the
same way regardless of the architecture (modulo some arch-specific
stuff).

In the end, it should be possible to avoid changing the behavior of
x86 and loongarch in this series.

> Which may look familiar at it's effectively patch 3 from v3 which was dealing
> with CPUs missing from DSDT (something we think doesn't happen).
>
> It might be possible to elide the arch_register_cpu() in
> make_present() but that will mean we use different flows in this patch set
> for the hotplug and initially present cases which is a bit messy.
>
> I've tested this lightly on arm64 and x86 ACPI + DT booting and it "seems" fine.

Sounds promising.

Thanks!

  reply	other threads:[~2024-04-10 13:28 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-01-31 16:48 [RFC PATCH v4 00/15] ACPI/arm64: add support for virtual cpu hotplug Russell King (Oracle)
2024-01-31 16:49 ` [PATCH RFC v4 01/15] ACPI: Only enumerate enabled (or functional) processor devices Russell King
2024-01-31 17:25   ` Miguel Luis
2024-02-15 20:10   ` Rafael J. Wysocki
2024-02-19  9:45     ` Jonathan Cameron
2024-02-20 11:30     ` Russell King (Oracle)
2024-02-21 13:01   ` Rafael J. Wysocki
2024-01-31 16:49 ` [PATCH RFC v4 02/15] ACPI: processor: Register all CPUs from acpi_processor_get_info() Russell King
2024-02-15 19:22   ` Rafael J. Wysocki
2024-02-20 11:27     ` Russell King (Oracle)
2024-02-20 15:13       ` Russell King (Oracle)
2024-02-20 16:24         ` Jonathan Cameron
2024-02-20 19:59           ` Rafael J. Wysocki
2024-02-21 12:04             ` Rafael J. Wysocki
2024-02-20 20:59     ` Thomas Gleixner
2024-03-22 18:53     ` Jonathan Cameron
2024-04-10 12:43       ` Jonathan Cameron
2024-04-10 13:28         ` Rafael J. Wysocki [this message]
2024-04-10 13:50           ` Jonathan Cameron
2024-04-10 14:19             ` Rafael J. Wysocki
2024-04-10 15:58               ` Jonathan Cameron
2024-04-10 18:56             ` Russell King (Oracle)
2024-04-10 19:08               ` Rafael J. Wysocki
2024-04-10 21:07                 ` Jonathan Cameron
2024-01-31 16:49 ` [PATCH RFC v4 03/15] ACPI: Move acpi_bus_trim_one() before acpi_scan_hot_remove() Russell King
2024-01-31 16:49 ` [PATCH RFC v4 04/15] ACPI: Rename acpi_processor_hotadd_init and remove pre-processor guards Russell King
2024-01-31 16:50 ` [PATCH RFC v4 05/15] ACPI: Add post_eject to struct acpi_scan_handler for cpu hotplug Russell King
2024-01-31 16:50 ` [PATCH RFC v4 06/15] ACPI: convert acpi_processor_post_eject() to use IS_ENABLED() Russell King (Oracle)
2024-01-31 16:50 ` [PATCH RFC v4 07/15] ACPI: Check _STA present bit before making CPUs not present Russell King
2024-01-31 16:50 ` [PATCH RFC v4 08/15] ACPI: Warn when the present bit changes but the feature is not enabled Russell King
2024-01-31 16:50 ` [PATCH RFC v4 09/15] arm64: acpi: Move get_cpu_for_acpi_id() to a header Russell King
2024-01-31 16:50 ` [PATCH RFC v4 10/15] irqchip/gic-v3: Don't return errors from gic_acpi_match_gicc() Russell King
2024-02-02 16:44   ` Jonathan Cameron
2024-01-31 16:50 ` [PATCH RFC v4 11/15] irqchip/gic-v3: Add support for ACPI's disabled but 'online capable' CPUs Russell King
2024-02-02 16:47   ` Jonathan Cameron
2024-01-31 16:50 ` [PATCH RFC v4 12/15] arm64: psci: Ignore DENIED CPUs Russell King
2024-04-11 11:35   ` Jonathan Cameron
2024-04-11 13:25     ` Jonathan Cameron
2024-01-31 16:50 ` [PATCH RFC v4 13/15] ACPI: add support to (un)register CPUs based on the _STA enabled bit Russell King
2024-01-31 16:50 ` [PATCH RFC v4 14/15] arm64: document virtual CPU hotplug's expectations Russell King
2024-02-02 17:04   ` Jonathan Cameron
2024-01-31 16:50 ` [PATCH RFC v4 15/15] cpumask: Add enabled cpumask for present CPUs that can be brought online Russell King

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