On Mon, 7 Nov 2016, Charles (Chas) Williams wrote:
> On 11/07/2016 11:19 AM, Thomas Gleixner wrote:
> > On Wed, 2 Nov 2016, Charles (Chas) Williams wrote:
> > > I don't know why the CPU's phys_proc_id is 2.
> >
> > max_physical_pkg_id gets initialized via:
> >
> > cpus = boot_cpu_data.x86_max_cores;
> > max_physical_pkg_id = DIV_ROUND_UP(MAX_LOCAL_APIC, ncpus);
> >
> > What's the value of boot_cpu_data.x86_max_cores and MAX_LOCAL_APIC?
>
> I have discovered that that is not the problem. smp_init_package_map()
> is calculating the physical core id using the following:
>
> for_each_present_cpu(cpu) {
> unsigned int apicid = apic->cpu_present_to_apicid(cpu);
>
> ...
> if (!topology_update_package_map(apicid, cpu))
> continue;
>
> ...
> int topology_update_package_map(unsigned int apicid, unsigned int cpu)
> {
> unsigned int new, pkg = apicid >>
> boot_cpu_data.x86_coreid_bits;
>
> But later when the secondary CPU's are identified they use a different
> calculation using the local APIC ID from the CPU's registers:
>
> static void generic_identify(struct cpuinfo_x86 *c)
> ...
> if (c->cpuid_level >= 0x00000001) {
> c->initial_apicid = (cpuid_ebx(1) >> 24) & 0xFF;
> ...
> c->phys_proc_id = c->initial_apicid;
>
> So at the end of identify_cpu() when the boot/hotplug assignment is
> put back:
>
> c->logical_proc_id = topology_phys_to_logical_pkg(c->phys_proc_id);
>
> topology_phys_to_logical_pkg() is returning an invalid logical processor
> since one isn't configured.
>
> It's not clear to me what the right thing to do is or which is right.
Nice detective work! So the issue is that the package mapping code honours
boot_cpu_data.x86_coreid_bit, while generic_identify does
not. boot_cpu_data.x86_coreid_bit is obviously 1 in your case. Tentative
fix below. I still need to gow through that maze and figure out what could
go wrong with that :(
Thanks,
tglx
8<------------------------
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -905,6 +905,8 @@ static void detect_null_seg_behavior(str
static void generic_identify(struct cpuinfo_x86 *c)
{
+ unsigned int pkg;
+
c->extended_cpuid_level = 0;
if (!have_cpuid_p())
@@ -929,7 +931,8 @@ static void generic_identify(struct cpui
c->apicid = c->initial_apicid;
# endif
#endif
- c->phys_proc_id = c->initial_apicid;
+ pkg = c->initial_apicid >> boot_cpu_data.x86_coreid_bits;
+ c->phys_proc_id = pkg;
}
get_model_name(c); /* Default name */
