linux-kernel - Re: [PATCH v8 05/16] ACPI: processor: Add acpi_get_processor

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Date: Tue, 30 Apr 2024 12:07:14 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Gavin Shan <gshan@...hat.com>
CC: Thomas Gleixner <tglx@...utronix.de>, Peter Zijlstra
	<peterz@...radead.org>, <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>, <kvmarm@...ts.linux.dev>,
	<x86@...nel.org>, Russell King <linux@...linux.org.uk>, "Rafael J . Wysocki"
	<rafael@...nel.org>, Miguel Luis <miguel.luis@...cle.com>, James Morse
	<james.morse@....com>, Salil Mehta <salil.mehta@...wei.com>, "Jean-Philippe
 Brucker" <jean-philippe@...aro.org>, Catalin Marinas
	<catalin.marinas@....com>, Will Deacon <will@...nel.org>, Marc Zyngier
	<maz@...nel.org>, Hanjun Guo <guohanjun@...wei.com>, Ingo Molnar
	<mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen
	<dave.hansen@...ux.intel.com>, <linuxarm@...wei.com>, <justin.he@....com>,
	<jianyong.wu@....com>, Lorenzo Pieralisi <lpieralisi@...nel.org>, "Sudeep
 Holla" <sudeep.holla@....com>
Subject: Re: [PATCH v8 05/16] ACPI: processor: Add
 acpi_get_processor_handle() helper

On Tue, 30 Apr 2024 14:26:06 +1000
Gavin Shan <gshan@...hat.com> wrote:

> On 4/26/24 23:51, Jonathan Cameron wrote:
> > If CONFIG_ACPI_PROCESSOR provide a helper to retrieve the
> > acpi_handle for a given CPU allowing access to methods
> > in DSDT.
> > 
> > Tested-by: Miguel Luis <miguel.luis@...cle.com>
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> > 
> > ---
> > v8: Code simplification suggested by Rafael.
> >      Fixup ;; spotted by Gavin
> > ---
> >   drivers/acpi/acpi_processor.c | 11 +++++++++++
> >   include/linux/acpi.h          |  7 +++++++
> >   2 files changed, 18 insertions(+)
> >   
> 
> Reviewed-by: Gavin Shan <gshan@...hat.com>
> 
Thanks,
> > diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> > index 3b180e21f325..ecc2721fecae 100644
> > --- a/drivers/acpi/acpi_processor.c
> > +++ b/drivers/acpi/acpi_processor.c
> > @@ -35,6 +35,17 @@ EXPORT_PER_CPU_SYMBOL(processors);
> >   struct acpi_processor_errata errata __read_mostly;
> >   EXPORT_SYMBOL_GPL(errata);
> >   
> > +acpi_handle acpi_get_processor_handle(int cpu)
> > +{
> > +	struct acpi_processor *pr;
> > +
> > +	pr = per_cpu(processors, cpu);
> > +	if (pr)
> > +		return pr->handle;
> > +
> > +	return NULL;
> > +}
> > +  
> 
> Maybe it's worthy to have more check here, something like below.
> However, it's also fine without the extra check.

We could harden this, but for now the call sites are only
int arch_(un)register_cpu() so if we get there with either
of these failing something went very wrong.

Maybe if it gets used more widely this defense would be wise.

Jonathan

> 
> 	if (cpu >= nr_cpu_ids || !cpu_possible(cpu))
> 		return NULL;
> 
> >   static int acpi_processor_errata_piix4(struct pci_dev *dev)
> >   {
> >   	u8 value1 = 0;
> > diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> > index 34829f2c517a..9844a3f9c4e5 100644
> > --- a/include/linux/acpi.h
> > +++ b/include/linux/acpi.h
> > @@ -309,6 +309,8 @@ int acpi_map_cpu(acpi_handle handle, phys_cpuid_t physid, u32 acpi_id,
> >   int acpi_unmap_cpu(int cpu);
> >   #endif /* CONFIG_ACPI_HOTPLUG_CPU */
> >   
> > +acpi_handle acpi_get_processor_handle(int cpu);
> > +
> >   #ifdef CONFIG_ACPI_HOTPLUG_IOAPIC
> >   int acpi_get_ioapic_id(acpi_handle handle, u32 gsi_base, u64 *phys_addr);
> >   #endif
> > @@ -1077,6 +1079,11 @@ static inline bool acpi_sleep_state_supported(u8 sleep_state)
> >   	return false;
> >   }
> >   
> > +static inline acpi_handle acpi_get_processor_handle(int cpu)
> > +{
> > +	return NULL;
> > +}
> > +
> >   #endif	/* !CONFIG_ACPI */
> >   
> >   extern void arch_post_acpi_subsys_init(void);  
> 
> Thanks,
> Gavin
>