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Date:   Fri, 19 Aug 2022 19:16:13 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Saurabh Singh Sengar <ssengar@linux.microsoft.com>
Cc:     ssengar@microsoft.com, mikelley@microsoft.com, tglx@linutronix.de,
        mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org,
        hpa@zytor.com, peterz@infradead.org, tim.c.chen@linux.intel.com,
        will@kernel.org, song.bao.hua@hisilicon.com,
        suravee.suthikulpanit@amd.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/cacheinfo: Don't use cpu_llc_shared_map for
 !CONFIG_SMP
Message-ID: <Yv/FXcOkB0BpUkVn@zn.tnic>
References: <1660148115-302-1-git-send-email-ssengar@linux.microsoft.com>
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 <Yv4pOz01nAkafiwd@zn.tnic>
 <20220818122925.GA8507@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net>
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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?

---
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