Commit 1340ccfa9a9a ("x86,sched: Allow topologies where NUMA nodes
share an LLC") added a vendor and model specific check to skip the
topology_sane() check for Intel's Sky Lake Server CPUs where NUMA
nodes shared an LLC.This topology is no longer a quirk for Intel CPUs as Ice Lake and Sapphire Rapids CPUs exhibit the same topology. Rather than maintain the quirk list, define a synthetic flag that directs the scheduler to allow this topology without warning for all Intel CPUs when NUMA is configured. Acked-by: Dave Hansen <[email protected]> Signed-off-by: Alison Schofield <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Tony Luck <[email protected]> Cc: Tim Chen <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Peter Zijlstra (Intel) <[email protected]> Cc: David Rientjes <[email protected]> Cc: Igor Mammedov <[email protected]> Cc: Prarit Bhargava <[email protected]> Cc: [email protected] --- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/kernel/cpu/intel.c | 15 +++++++++++++++ arch/x86/kernel/smpboot.c | 23 ++--------------------- 3 files changed, 18 insertions(+), 21 deletions(-) diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 84b887825f12..bec74b90d3d6 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -421,5 +421,6 @@ #define X86_BUG_TAA X86_BUG(22) /* CPU is affected by TSX Async Abort(TAA) */ #define X86_BUG_ITLB_MULTIHIT X86_BUG(23) /* CPU may incur MCE during certain page attribute changes */ #define X86_BUG_SRBDS X86_BUG(24) /* CPU may leak RNG bits if not mitigated */ +#define X86_BUG_NUMA_SHARES_LLC X86_BUG(25) /* CPU may enumerate an LLC shared by multiple NUMA nodes */ #endif /* _ASM_X86_CPUFEATURES_H */ diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 816fdbec795a..027348261080 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -719,6 +719,21 @@ static void init_intel(struct cpuinfo_x86 *c) tsx_disable(); split_lock_init(); + + /* + * Set X86_BUG_NUMA_SHARES_LLC to allow topologies where NUMA + * nodes share an LLC. In Sub-NUMA Clustering mode Intel CPUs + * may enumerate an LLC as shared by multiple NUMA nodes. The + * LLC is shared for off-package data access but private to + * the NUMA node for on-package access. This topology first + * appeared in SKYLAKE_X. It was treated as a quirk and allowed. + * This topology reappeared in ICELAKE_X and SAPPHIRERAPIDS_X. + * Rather than maintain a list of quirk CPUS, allow this topology + * on all Intel CPUs with NUMA configured. When this X86_BUG is + * set, the scheduler accepts this topology without warning. + */ + if (IS_ENABLED(CONFIG_NUMA)) + set_cpu_bug(c, X86_BUG_NUMA_SHARES_LLC); } #ifdef CONFIG_X86_32 diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 117e24fbfd8a..7d05c3552795 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -458,26 +458,6 @@ static bool match_smt(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o) return false; } -/* - * Define snc_cpu[] for SNC (Sub-NUMA Cluster) CPUs. - * - * These are Intel CPUs that enumerate an LLC that is shared by - * multiple NUMA nodes. The LLC on these systems is shared for - * off-package data access but private to the NUMA node (half - * of the package) for on-package access. - * - * CPUID (the source of the information about the LLC) can only - * enumerate the cache as being shared *or* unshared, but not - * this particular configuration. The CPU in this case enumerates - * the cache to be shared across the entire package (spanning both - * NUMA nodes). - */ - -static const struct x86_cpu_id snc_cpu[] = { - X86_MATCH_INTEL_FAM6_MODEL(SKYLAKE_X, NULL), - {} -}; - static bool match_llc(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o) { int cpu1 = c->cpu_index, cpu2 = o->cpu_index; @@ -495,7 +475,8 @@ static bool match_llc(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o) * means 'c' does not share the LLC of 'o'. This will be * reflected to userspace. */ - if (!topology_same_node(c, o) && x86_match_cpu(snc_cpu)) + if (!topology_same_node(c, o) && + boot_cpu_has_bug(X86_BUG_NUMA_SHARES_LLC)) return false; return topology_sane(c, o, "llc"); -- 2.20.1
