linux-kernel - Re: [External] Re: [PATCH v3 1/1] arch_topology: move parse_acpi

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Message-ID: <20250922-buffalo-of-hypothetical-downpour-d2a47c@sudeepholla>
Date: Mon, 22 Sep 2025 10:01:17 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: yunhui cui <cuiyunhui@...edance.com>
Cc: catalin.marinas@....com, will@...nel.org, gregkh@...uxfoundation.org,
	rafael@...nel.org, dakr@...nel.org, beata.michalska@....com,
	ptsm@...ux.microsoft.com, sumitg@...dia.com,
	yangyicong@...ilicon.com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [External] Re: [PATCH v3 1/1] arch_topology: move
 parse_acpi_topology() to common code

On Mon, Sep 22, 2025 at 10:18:57AM +0800, yunhui cui wrote:
> Hi Sudeep,
> 
> On Fri, Sep 19, 2025 at 10:05 PM Sudeep Holla <sudeep.holla@....com> wrote:

[...]

> >
> > Just thinking if it makes sense keep acpi_cpu_is_threaded generic without
> > the need for weak definition.
> >
> > Additional note: not sure why you haven't moved this under CONFIG_ARM64/RISCV as
> > done with other code.
> >
> > bool __init acpi_cpu_is_threaded(int cpu)
> > {
> >         int is_threaded = acpi_pptt_cpu_is_thread(cpu);
> >
> >         /*
> >          * if the PPTT doesn't have thread information, check for architecture
> >          * specific fallback if available
> >          */
> >         if (is_threaded < 0)
> >                 is_threaded = arch_cpu_is_threaded();
> >
> >         return !!is_threaded;
> > }
> >
> > Then you can just have the define in
> >
> > #define arch_cpu_is_threaded() (read_cpuid_mpidr() & MPIDR_MT_BITMASK)
> >
> > in arch/arm64/include/asm/topology.h
> >
> > and
> >
> > +#ifndef arch_cpu_is_threaded
> > +#define arch_cpu_is_threaded           (0)
> > +#endif
> >
> > in include/linux/arch_topology.h
> >
> > Thoughts ?
> 
> If placed in include/linux/arch_topology.h, there is a possibility
> that "arch_cpu_is_threaded" will be redefined.
>

Why is that a problem ? We want arch to override the default definition
if and when required.

-- 
Regards,
Sudeep