On 2019/2/24 18:04, Brice Goglin wrote:

Le 19/02/2019 à 04:40, Len Brown a écrit :

quoted

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index ccd1f2a8e557..4250a87f57db 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c

@@ -393,6 +393,7 @@ 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 &&
+		    c->cpu_die_id == o->cpu_die_id &&
  		    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");

@@ -404,6 +405,7 @@ static bool match_smt(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
  		}
  
  	} else if (c->phys_proc_id == o->phys_proc_id &&
+		   c->cpu_die_id == o->cpu_die_id &&
  		   c->cpu_core_id == o->cpu_core_id) {
  		return topology_sane(c, o, "smt");
  	}

@@ -461,7 +463,7 @@ static bool match_llc(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
   */
  static bool match_die(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
  {
-	if (c->phys_proc_id == o->phys_proc_id)
+	if (c->cpu_die_id == o->cpu_die_id)
  		return true;
  	return false;
  }

Hello Len,

I am testing your patches in a VM with CPUID.1f QEMU patches (author Like Xu is CC'ed),
booted to get 2 packages with 1 NUMA node each and 2 dies each:

-smp cpus=16,threads=2,cores=2,dies=2,sockets=2 -numa node,cpus=0-7,nodeid=0 -numa node,cpus=8-15,nodeid=1

sysfs files expose wrong information:
core_siblings contains threads of the local die AND of die with same number in other processors,
eg cpu 0-3 and 8-11 instead of 0-3 only.

The issue is that you seem to assume that die ids will always be unique across multiple packages.

I don't think the intel MCP topolohgy has this global uniqueness 
assumption for die_id according to CPUID.1F SDM.

Is this a valid assumption? If so, QEMU patches should be fixed.
If not, I fixed the issue by changing match_die() to check both phys_proc_id and cpu_die_id:

static bool match_die(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
{
	if (c->phys_proc_id == o->phys_proc_id && c->cpu_die_id == o->cpu_die_id)
  		return true;
	return false;
}

Thanks
Brice