[PATCH V3 4/8] x86/topology: Fix multiple packages shown on a single-package system

From: Zhang Rui
Date: Thu Sep 22 2022 - 09:35:44 EST


CPUID.1F/B does not emumerate Package level explicitly, instead, all the
APIC-ID bits above the enumerated levels are assumed to be package ID
bits.

Current code gets package ID by shifting out all the APIC-ID bits that
Linux supports, rather than shifting out all the APIC-ID bits that
CPUID.1F enumerates. This introduces problems when CPUID.1F enumerates a
level that Linux does not support.

For example, on an AlderLake-N platform, there are 2 Ecore Modules, which
has 4 atom cores in each module, in a single package.
Linux does not support Module level and interprets the Module ID bits as
package ID and erroneously reports a multi module system as a
multi-package system.

Fix this by using APIC-ID bits above all the CPUID.1F enumerated levels as
package ID.

Suggested-by: Len Brown <len.brown@xxxxxxxxx>
Reviewed-by: Len Brown <len.brown@xxxxxxxxx>
Signed-off-by: Zhang Rui <rui.zhang@xxxxxxxxx>
---
arch/x86/kernel/cpu/topology.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
index 132a2de44d2f..f7592814e5d5 100644
--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -96,6 +96,7 @@ int detect_extended_topology(struct cpuinfo_x86 *c)
unsigned int ht_mask_width, core_plus_mask_width, die_plus_mask_width;
unsigned int core_select_mask, core_level_siblings;
unsigned int die_select_mask, die_level_siblings;
+ unsigned int pkg_mask_width;
bool die_level_present = false;
int leaf;

@@ -111,10 +112,10 @@ int detect_extended_topology(struct cpuinfo_x86 *c)
core_level_siblings = smp_num_siblings = LEVEL_MAX_SIBLINGS(ebx);
core_plus_mask_width = ht_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
die_level_siblings = LEVEL_MAX_SIBLINGS(ebx);
- die_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
+ pkg_mask_width = die_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);

sub_index = 1;
- do {
+ while (true) {
cpuid_count(leaf, sub_index, &eax, &ebx, &ecx, &edx);

/*
@@ -132,8 +133,13 @@ int detect_extended_topology(struct cpuinfo_x86 *c)
die_plus_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
}

+ if (LEAFB_SUBTYPE(ecx) != INVALID_TYPE)
+ pkg_mask_width = BITS_SHIFT_NEXT_LEVEL(eax);
+ else
+ break;
+
sub_index++;
- } while (LEAFB_SUBTYPE(ecx) != INVALID_TYPE);
+ }

core_select_mask = (~(-1 << core_plus_mask_width)) >> ht_mask_width;
die_select_mask = (~(-1 << die_plus_mask_width)) >>
@@ -148,7 +154,7 @@ int detect_extended_topology(struct cpuinfo_x86 *c)
}

c->phys_proc_id = apic->phys_pkg_id(c->initial_apicid,
- die_plus_mask_width);
+ pkg_mask_width);
/*
* Reinit the apicid, now that we have extended initial_apicid.
*/
--
2.25.1