Re: [PATCH] x86/cacheinfo: Don't use cpu_llc_shared_map for !CONFIG_SMP

Borislav Petkov
2022-08-19T17:49:06Z

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.