linux-kernel - Re: [PATCH V2 1/1] x86/topology: fix erroneous smp_num

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Date:   Mon, 13 Mar 2023 02:05:25 +0000
From:   "Zhang, Rui" <rui.zhang@...el.com>
To:     "peterz@...radead.org" <peterz@...radead.org>
CC:     "Brown, Len" <len.brown@...el.com>,
        "zhang.jia@...ux.alibaba.com" <zhang.jia@...ux.alibaba.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2 1/1] x86/topology: fix erroneous smp_num_siblings on
 Intel Hybrid platform

On Tue, 2023-02-21 at 16:34 +0800, Zhang Rui wrote:
> Hi, Peter,
> 
> > > ---
> > >  arch/x86/kernel/cpu/topology.c | 5 +++--
> > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/arch/x86/kernel/cpu/topology.c
> > > b/arch/x86/kernel/cpu/topology.c
> > > index 5e868b62a7c4..0270925fe013 100644
> > > --- a/arch/x86/kernel/cpu/topology.c
> > > +++ b/arch/x86/kernel/cpu/topology.c
> > > @@ -79,7 +79,7 @@ int detect_extended_topology_early(struct
> > > cpuinfo_x86 *c)
> > >  	 * initial apic id, which also represents 32-bit extended
> > > x2apic id.
> > >  	 */
> > >  	c->initial_apicid = edx;
> > > -	smp_num_siblings = LEVEL_MAX_SIBLINGS(ebx);
> > > +	smp_num_siblings = max_t(int, smp_num_siblings,
> > > LEVEL_MAX_SIBLINGS(ebx));
> > >  #endif
> > >  	return 0;
> > >  }
> > > @@ -109,7 +109,8 @@ int detect_extended_topology(struct
> > > cpuinfo_x86
> > > *c)
> > >  	 */
> > >  	cpuid_count(leaf, SMT_LEVEL, &eax, &ebx, &ecx, &edx);
> > >  	c->initial_apicid = edx;
> > > -	core_level_siblings = smp_num_siblings =
> > > LEVEL_MAX_SIBLINGS(ebx);
> > > +	core_level_siblings = LEVEL_MAX_SIBLINGS(ebx);
> > > +	smp_num_siblings = max_t(int, smp_num_siblings,
> > > LEVEL_MAX_SIBLINGS(ebx));
> > >  	core_plus_mask_width = ht_mask_width =
> > > BITS_SHIFT_NEXT_LEVEL(eax);
> > >  	die_level_siblings = LEVEL_MAX_SIBLINGS(ebx);
> > >  	pkg_mask_width = die_plus_mask_width =
> > > BITS_SHIFT_NEXT_LEVEL(eax);
> > 
> > Seems ok, but perhaps you can stick an 'int' cast in
> > LEVEL_MAX_SIGLINGS instead and write a simpler max() -- and/or
> > convert
> > smt_num_siblings to unsigned int.
> > 
> yeah, it is doable. I'd prefer to use the current version to keep
> this
> fix simpler if you don't mind.
> 
> > Regardless,
> > 
> > Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> 
> Thanks for your ACK.

Hi, all,

Despite the discussions about future improvements in the cover letter
of this patch series, is there any further changes needed for this one?

thanks,
rui