> -----Original Message----- > From: Borislav Petkov [mailto:[email protected]] > Sent: Wednesday, February 1, 2017 3:03 PM > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > index 548da5a8013e..f06fa338076b 100644 > --- a/arch/x86/kernel/smpboot.c > +++ b/arch/x86/kernel/smpboot.c > @@ -433,9 +433,13 @@ static bool match_smt(struct cpuinfo_x86 *c, struct > cpuinfo_x86 *o) > int cpu1 = c->cpu_index, cpu2 = o->cpu_index; > > if (c->phys_proc_id == o->phys_proc_id && > - per_cpu(cpu_llc_id, cpu1) == per_cpu(cpu_llc_id, cpu2) && > - c->cpu_core_id == o->cpu_core_id) > - return topology_sane(c, o, "smt"); > + per_cpu(cpu_llc_id, cpu1) == per_cpu(cpu_llc_id, cpu2)) { > + if (c->cpu_core_id == o->cpu_core_id) > + return topology_sane(c, o, "smt"); > + > + if (c->cu_id == o->cu_id) > + return topology_sane(c, o, "smt"); > + } >
This hunk won't work for SMT enabled systems. It'll cause all threads under an LLC to be considered SMT siblings. For example, threads 0 &2 will have different cpu_core_id, so the first check will fail. But it'll match on the second check since cu_id will be initialized to 0. To get around this we can set cu_id for all TOPOEXT systems, and update cpu_core_id, etc. for SMT enabled systems. This way we can just change cpu_core_id to cu_id in match_smt(). I tested this patch, with the above changes, on a Fam17h SMT enabled system. I'll test with SMT disabled and also on a fully-loaded Fam15h system soon. Thanks, Yazen
