2022-10-14 09:42:38

by Zhang, Rui

Subject: [PATCH V4 4/4] x86/topology: Fix duplicated core ID within a package

Today, core ID is assumed to be unique within each package.

But an AlderLake-N platform adds a Module level between core and package,
Linux excludes the unknown modules bits from the core ID, resulting in
duplicate core ID's.

To keep core ID unique within a package, Linux must include all APIC-ID
bits for known or un-known levels above the core and below the package
in the core ID.

It is important to understand that core ID's have always come directly
from the APIC-ID encoding, which comes from the BIOS. Thus there is no
guarantee that they start at 0, or that they are contiguous.
As such, naively using them for array indexes can be problematic.

Fixes: 7745f03eb395 ("x86/topology: Add CPUID.1F multi-die/package support")
Cc: [email protected]
Suggested-by: Len Brown <[email protected]>
Signed-off-by: Zhang Rui <[email protected]>
Reviewed-by: Len Brown <[email protected]>
---
arch/x86/kernel/cpu/topology.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
index f7592814e5d5..5e868b62a7c4 100644
--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -141,7 +141,7 @@ int detect_extended_topology(struct cpuinfo_x86 *c)
sub_index++;
}

- core_select_mask = (~(-1 << core_plus_mask_width)) >> ht_mask_width;
+ core_select_mask = (~(-1 << pkg_mask_width)) >> ht_mask_width;
die_select_mask = (~(-1 << die_plus_mask_width)) >>
core_plus_mask_width;

--
2.25.1

2022-10-17 20:00:21

by tip-bot2 for Alexey Makhalov

Subject: [tip: x86/urgent] x86/topology: Fix duplicated core ID within a package

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID: 71eac7063698b7d7b8fafb1683ac24a034541141
Gitweb: https://git.kernel.org/tip/71eac7063698b7d7b8fafb1683ac24a034541141
Author: Zhang Rui <[email protected]>
AuthorDate: Fri, 14 Oct 2022 17:01:47 +08:00
Committer: Dave Hansen <[email protected]>
CommitterDate: Mon, 17 Oct 2022 11:58:52 -07:00

x86/topology: Fix duplicated core ID within a package

Today, core ID is assumed to be unique within each package.

But an AlderLake-N platform adds a Module level between core and package,
Linux excludes the unknown modules bits from the core ID, resulting in
duplicate core ID's.

To keep core ID unique within a package, Linux must include all APIC-ID
bits for known or unknown levels above the core and below the package
in the core ID.

It is important to understand that core ID's have always come directly
from the APIC-ID encoding, which comes from the BIOS. Thus there is no
guarantee that they start at 0, or that they are contiguous.
As such, naively using them for array indexes can be problematic.

[ dhansen: un-known -> unknown ]

Fixes: 7745f03eb395 ("x86/topology: Add CPUID.1F multi-die/package support")
Suggested-by: Len Brown <[email protected]>
Signed-off-by: Zhang Rui <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
Reviewed-by: Len Brown <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
---
arch/x86/kernel/cpu/topology.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
index f759281..5e868b6 100644
--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -141,7 +141,7 @@ int detect_extended_topology(struct cpuinfo_x86 *c)
sub_index++;
}

- core_select_mask = (~(-1 << core_plus_mask_width)) >> ht_mask_width;
+ core_select_mask = (~(-1 << pkg_mask_width)) >> ht_mask_width;
die_select_mask = (~(-1 << die_plus_mask_width)) >>
core_plus_mask_width;