linux-kernel - Re: [PATCH] x86/cacheinfo: Don't use cpu_llc_shared_map for !CONFIG

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Date:   Fri, 19 Aug 2022 10:46:59 -0700
From:   Saurabh Singh Sengar <ssengar@...ux.microsoft.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     ssengar@...rosoft.com, mikelley@...rosoft.com, tglx@...utronix.de,
        mingo@...hat.com, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, peterz@...radead.org, tim.c.chen@...ux.intel.com,
        will@...nel.org, song.bao.hua@...ilicon.com,
        suravee.suthikulpanit@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/cacheinfo: Don't use cpu_llc_shared_map for
 !CONFIG_SMP

On Fri, Aug 19, 2022 at 07:16:13PM +0200, Borislav Petkov wrote:
> On Thu, Aug 18, 2022 at 05:29:25AM -0700, Saurabh Singh Sengar wrote:
> > Boot latest linux kernel on AMD CPU, having CONGIG_SMP=n. Once booted
> > execute lscpu (just lscpu without any argument ), this will cause
> > segfault. Please make a note issue is observed with 2.34 version
> > (default lscpu version with Ubuntu 20.04.4) of lscpu.
> 
> Does that fix it?

Yes, this patch fixes this segfault.

- Saurabh

> 
> ---
> diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> index 81a0211a372d..a73bced40e24 100644
> --- a/arch/x86/include/asm/smp.h
> +++ b/arch/x86/include/asm/smp.h
> @@ -21,16 +21,6 @@ DECLARE_PER_CPU_READ_MOSTLY(u16, cpu_llc_id);
>  DECLARE_PER_CPU_READ_MOSTLY(u16, cpu_l2c_id);
>  DECLARE_PER_CPU_READ_MOSTLY(int, cpu_number);
>  
> -static inline struct cpumask *cpu_llc_shared_mask(int cpu)
> -{
> -	return per_cpu(cpu_llc_shared_map, cpu);
> -}
> -
> -static inline struct cpumask *cpu_l2c_shared_mask(int cpu)
> -{
> -	return per_cpu(cpu_l2c_shared_map, cpu);
> -}
> -
>  DECLARE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_cpu_to_apicid);
>  DECLARE_EARLY_PER_CPU_READ_MOSTLY(u32, x86_cpu_to_acpiid);
>  DECLARE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_bios_cpu_apicid);
> @@ -172,6 +162,16 @@ extern int safe_smp_processor_id(void);
>  # define safe_smp_processor_id()	smp_processor_id()
>  #endif
>  
> +static inline struct cpumask *cpu_llc_shared_mask(int cpu)
> +{
> +	return per_cpu(cpu_llc_shared_map, cpu);
> +}
> +
> +static inline struct cpumask *cpu_l2c_shared_mask(int cpu)
> +{
> +	return per_cpu(cpu_l2c_shared_map, cpu);
> +}
> +
>  #else /* !CONFIG_SMP */
>  #define wbinvd_on_cpu(cpu)     wbinvd()
>  static inline int wbinvd_on_all_cpus(void)
> @@ -179,6 +179,11 @@ static inline int wbinvd_on_all_cpus(void)
>  	wbinvd();
>  	return 0;
>  }
> +
> +static inline struct cpumask *cpu_llc_shared_mask(int cpu)
> +{
> +	return (struct cpumask *)cpumask_of(0);
> +}
>  #endif /* CONFIG_SMP */
>  
>  extern unsigned disabled_cpus;
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> https://people.kernel.org/tglx/notes-about-netiquette