linux-kernel - [tip: x86/urgent] x86/topology: Fix duplicated core ID within a package

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Date:   Mon, 17 Oct 2022 19:11:21 -0000
From:   "tip-bot2 for Zhang Rui" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Len Brown <len.brown@...el.com>, Zhang Rui <rui.zhang@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        stable@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
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 <rui.zhang@...el.com>
AuthorDate:    Fri, 14 Oct 2022 17:01:47 +08:00
Committer:     Dave Hansen <dave.hansen@...ux.intel.com>
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 <len.brown@...el.com>
Signed-off-by: Zhang Rui <rui.zhang@...el.com>
Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Reviewed-by: Len Brown <len.brown@...el.com>
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/20221014090147.1836-5-rui.zhang@intel.com
---
 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;