linux-kernel - [tip:x86/urgent] x86/CPU/AMD: Fix LLC ID bit-shift calculation

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Date:   Fri, 22 Jun 2018 12:24:51 -0700
From:   tip-bot for Suravee Suthikulpanit <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     suravee.suthikulpanit@....com, tglx@...utronix.de, bp@...e.de,
        mingo@...nel.org, hpa@...or.com, linux-kernel@...r.kernel.org
Subject: [tip:x86/urgent] x86/CPU/AMD: Fix LLC ID bit-shift calculation

Commit-ID:  964d978433a4b9aa1368ff71227ca0027dd1e32f
Gitweb:     https://git.kernel.org/tip/964d978433a4b9aa1368ff71227ca0027dd1e32f
Author:     Suravee Suthikulpanit <suravee.suthikulpanit@....com>
AuthorDate: Wed, 13 Jun 2018 13:43:10 -0500
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 22 Jun 2018 21:21:49 +0200

x86/CPU/AMD: Fix LLC ID bit-shift calculation

The current logic incorrectly calculates the LLC ID from the APIC ID.

Unless specified otherwise, the LLC ID should be calculated by removing
the Core and Thread ID bits from the least significant end of the APIC
ID. For more info, see "ApicId Enumeration Requirements" in any Fam17h
PPR document.

[ bp: Improve commit message. ]

Fixes: 68091ee7ac3c ("Calculate last level cache ID from number of sharing threads")
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1528915390-30533-1-git-send-email-suravee.suthikulpanit@amd.com
---
 arch/x86/kernel/cpu/cacheinfo.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/cacheinfo.c b/arch/x86/kernel/cpu/cacheinfo.c
index 38354c66df81..0c5fcbd998cf 100644
--- a/arch/x86/kernel/cpu/cacheinfo.c
+++ b/arch/x86/kernel/cpu/cacheinfo.c
@@ -671,7 +671,7 @@ void cacheinfo_amd_init_llc_id(struct cpuinfo_x86 *c, int cpu, u8 node_id)
 			num_sharing_cache = ((eax >> 14) & 0xfff) + 1;
 
 		if (num_sharing_cache) {
-			int bits = get_count_order(num_sharing_cache) - 1;
+			int bits = get_count_order(num_sharing_cache);
 
 			per_cpu(cpu_llc_id, cpu) = c->apicid >> bits;
 		}