From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Russell King <rmk+kernel@armlinux.org.uk>
Cc: 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>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>,
"Rafael J. Wysocki" <rafael@kernel.org>
Subject: Re: [PATCH RFC v4 02/15] ACPI: processor: Register all CPUs from acpi_processor_get_info()
Date: Thu, 15 Feb 2024 20:22:29 +0100 [thread overview]
Message-ID: <CAJZ5v0iiJpUWq5GMSnKFWQTzn_bdwoQz9m=hDaXNg4Lj_ePF4g@mail.gmail.com> (raw)
In-Reply-To: <E1rVDmU-0027YP-Jz@rmk-PC.armlinux.org.uk>
On Wed, Jan 31, 2024 at 5:50 PM Russell King <rmk+kernel@armlinux.org.uk> wrote:
>
> From: James Morse <james.morse@arm.com>
>
> To allow ACPI to skip the call to arch_register_cpu() when the _STA
> value indicates the CPU can't be brought online right now, move the
> arch_register_cpu() call into acpi_processor_get_info().
>
> Systems can still be booted with 'acpi=off', or not include an
> ACPI description at all. For these, the CPUs continue to be
> registered by cpu_dev_register_generic().
>
> This moves the CPU register logic back to a subsys_initcall(),
> while the memory nodes will have been registered earlier.
>
> Signed-off-by: James Morse <james.morse@arm.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> Tested-by: Miguel Luis <miguel.luis@oracle.com>
> Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
> Tested-by: Jianyong Wu <jianyong.wu@arm.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
> ---
> Changes since RFC v2:
> * Fixup comment in acpi_processor_get_info() (Gavin Shan)
> * Add comment in cpu_dev_register_generic() (Gavin Shan)
> ---
> drivers/acpi/acpi_processor.c | 12 ++++++++++++
> drivers/base/cpu.c | 6 +++++-
> 2 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> index cf7c1cca69dd..a68c475cdea5 100644
> --- a/drivers/acpi/acpi_processor.c
> +++ b/drivers/acpi/acpi_processor.c
> @@ -314,6 +314,18 @@ static int acpi_processor_get_info(struct acpi_device *device)
> cpufreq_add_device("acpi-cpufreq");
> }
>
> + /*
> + * Register CPUs that are present. get_cpu_device() is used to skip
> + * duplicate CPU descriptions from firmware.
> + */
> + if (!invalid_logical_cpuid(pr->id) && cpu_present(pr->id) &&
> + !get_cpu_device(pr->id)) {
> + int ret = arch_register_cpu(pr->id);
> +
> + if (ret)
> + return ret;
> + }
> +
> /*
> * Extra Processor objects may be enumerated on MP systems with
> * less than the max # of CPUs. They should be ignored _iff
This is interesting, because right below there is the following code:
if (invalid_logical_cpuid(pr->id) || !cpu_present(pr->id)) {
int ret = acpi_processor_hotadd_init(pr);
if (ret)
return ret;
}
and acpi_processor_hotadd_init() essentially calls arch_register_cpu()
with some extra things around it (more about that below).
I do realize that acpi_processor_hotadd_init() is defined under
CONFIG_ACPI_HOTPLUG_CPU, so for the sake of the argument let's
consider an architecture where CONFIG_ACPI_HOTPLUG_CPU is set.
So why are the two conditionals that almost contradict each other both
needed? It looks like the new code could be combined with
acpi_processor_hotadd_init() to do the right thing in all cases.
Now, acpi_processor_hotadd_init() does some extra things that look
like they should be done by the new code too.
1. It checks invalid_phys_cpuid() which appears to be a good idea to me.
2. It uses locking around arch_register_cpu() which doesn't seem
unreasonable either.
3. It calls acpi_map_cpu() and I'm not sure why this is not done by
the new code.
The only thing that can be dropped from it is the _STA check AFAICS,
because acpi_processor_add() won't even be called if the CPU is not
present (and not enabled after the first patch).
So why does the code not do 1 - 3 above?
> 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.
>
> for_each_present_cpu(i) {
> --
next prev parent reply other threads:[~2024-02-15 19:22 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 [this message]
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
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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