From: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: 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 14:50:05 +0100 [thread overview]
Message-ID: <20240410145005.00003050@Huawei.com> (raw)
In-Reply-To: <CAJZ5v0ggD042sfz3jDXQVDUxQZu_AWaF2ox-Me8CvFeRB8nczw@mail.gmail.com>
On Wed, 10 Apr 2024 15:28:18 +0200
"Rafael J. Wysocki" <rafael@kernel.org> wrote:
> 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.
Ok. That would end up looking much more like the original code I think.
So we wouldn't have this late registration at all, or keep it for DT
on arm64? I'm not sure that's a clean solution though leaves
the x86 path alone.
If we get rid of this catch all, solution would be to move the
!acpi_disabled check into the arm64 version of arch_cpu_register()
because we would only want the delayed registration path to be
used on ACPI cases where the question of CPU availability can't
yet be resolved.
>
> 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).
If I understand correctly, in acpi_processor_get_info() we'd end up
with a similar check on whether it was already registered (the x86 path)
or had be deferred (arm64 / acpi).
>
> In the end, it should be possible to avoid changing the behavior of
> x86 and loongarch in this series.
Possible, yes, but result if I understand correctly is we end up with
very different flows and replication of functionality between the
early registration and the late one. I'm fine with that if you prefer it!
>
> > 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.
Possibly not that relevant though if proposal is to drop this approach. :(
At least I now have test setups!
Jonathan
>
> Thanks!
next prev parent reply other threads:[~2024-04-10 13:50 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
2024-04-10 13:50 ` Jonathan Cameron [this message]
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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