linux-kernel - Re: [PATCH RFC v4 02/15] ACPI: processor: Register all CPUs from acpi_processor_get_info()

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Date: Wed, 10 Apr 2024 13:43:18 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: "Rafael J. Wysocki" <rafael@...nel.org>
CC: Russell King <rmk+kernel@...linux.org.uk>, <linux-pm@...r.kernel.org>,
	<loongarch@...ts.linux.dev>, <linux-acpi@...r.kernel.org>,
	<linux-arch@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-riscv@...ts.infradead.org>,
	<kvmarm@...ts.linux.dev>, <x86@...nel.org>,
	<acpica-devel@...ts.linuxfoundation.org>, <linux-csky@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <linux-ia64@...r.kernel.org>,
	<linux-parisc@...r.kernel.org>, Salil Mehta <salil.mehta@...wei.com>,
	Jean-Philippe Brucker <jean-philippe@...aro.org>, <jianyong.wu@....com>,
	<justin.he@....com>, James Morse <james.morse@....com>
Subject: Re: [PATCH RFC v4 02/15] ACPI: processor: Register all CPUs from
 acpi_processor_get_info()

> >   
> > > 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);

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.

Jonathan

> >   
> > >
> > >         for_each_present_cpu(i) {
> > > --    
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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