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Re: [PATCH v3 1/2] x86/AMD: Fix cpu_llc_id for AMD Fam17h systems

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Lemme clean up the commit message a bit more and add tags:

---
From: Yazen Ghannam <Yazen.Ghannam@amd.com>
Date: Tue, 1 Nov 2016 11:51:02 -0500
Subject: [PATCH] x86/AMD: Fix cpu_llc_id for AMD Fam17h systems

cpu_llc_id (Last Level Cache ID) derivation on AMD Fam17h has an
underflow bug when extracting the socket_id value. It starts from 0
so subtracting 1 from it will result in an invalid value. This breaks
scheduling topology later on since the cpu_llc_id will be incorrect.

The APIC ID is preset in APICx020 for bits 3 and above: they contain the
core complex, node and socket IDs.

The LLC is at the core complex level so we can find a unique cpu_llc_id
by right shifting the APICID by 3 because then the least significant bit
will be the Core Complex ID.

Signed-off-by: Yazen Ghannam <Yazen.Ghannam@amd.com>
Tested-by: Borislav Petkov <bp@suse.de>
Cc: Aravind Gopalakrishnan  <aravindksg.lkml@gmail.com>
Cc: <stable@vger.kernel.org> # v4.4..
Cc: x86-ml <x86@kernel.org>
Link: http://lkml.kernel.org/r/1478019063-2632-1-git-send-email-Yazen.Ghannam@amd.com
Fixes: 3849e91f571d ("x86/AMD: Fix last level cache topology for AMD Fam17h systems")
[ Boris: cleanup commit message. ]
Signed-off-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/kernel/cpu/amd.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index b81fe2d63e15..1e81a37c034e 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -347,7 +347,6 @@ static void amd_detect_cmp(struct cpuinfo_x86 *c)
 #ifdef CONFIG_SMP
 	unsigned bits;
 	int cpu = smp_processor_id();
-	unsigned int socket_id, core_complex_id;
 
 	bits = c->x86_coreid_bits;
 	/* Low order bits define the core id (index of core in socket) */
@@ -365,10 +364,7 @@ static void amd_detect_cmp(struct cpuinfo_x86 *c)
 	 if (c->x86 != 0x17 || !cpuid_edx(0x80000006))
 		return;
 
-	socket_id	= (c->apicid >> bits) - 1;
-	core_complex_id	= (c->apicid & ((1 << bits) - 1)) >> 3;
-
-	per_cpu(cpu_llc_id, cpu) = (socket_id << 3) | core_complex_id;
+	per_cpu(cpu_llc_id, cpu) = c->apicid >> 3;
 #endif
 }
 
-- 
2.10.0

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
-- 

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Re: [PATCH v3 1/2] x86/AMD: Fix cpu_llc_id for AMD Fam17h systems Borislav Petkov <bp@suse.de> - 2016-11-02 21:20 +0100
  Re: [PATCH v3 1/2] x86/AMD: Fix cpu_llc_id for AMD Fam17h systems Ingo Molnar <mingo@kernel.org> - 2016-11-07 08:40 +0100
    Re: [PATCH v3 1/2] x86/AMD: Fix cpu_llc_id for AMD Fam17h systems Borislav Petkov <bp@suse.de> - 2016-11-07 10:30 +0100
      Re: [PATCH v3 1/2] x86/AMD: Fix cpu_llc_id for AMD Fam17h systems Ingo Molnar <mingo@kernel.org> - 2016-11-07 15:10 +0100
        Re: [PATCH v3 1/2] x86/AMD: Fix cpu_llc_id for AMD Fam17h systems Borislav Petkov <bp@suse.de> - 2016-11-07 17:00 +0100
          Re: [PATCH v3 1/2] x86/AMD: Fix cpu_llc_id for AMD Fam17h systems Ingo Molnar <mingo@kernel.org> - 2016-11-08 07:40 +0100
            Re: [PATCH v3 1/2] x86/AMD: Fix cpu_llc_id for AMD Fam17h systems Borislav Petkov <bp@suse.de> - 2016-11-08 09:40 +0100
              Re: [PATCH v3 1/2] x86/AMD: Fix cpu_llc_id for AMD Fam17h systems Ingo Molnar <mingo@kernel.org> - 2016-11-08 11:30 +0100
                Re: [PATCH v3 1/2] x86/AMD: Fix cpu_llc_id for AMD Fam17h systems Borislav Petkov <bp@suse.de> - 2016-11-08 12:10 +0100
                Re: [PATCH v3 1/2] x86/AMD: Fix cpu_llc_id for AMD Fam17h systems Ingo Molnar <mingo@kernel.org> - 2016-11-08 16:00 +0100
                Re: [PATCH v3 1/2] x86/AMD: Fix cpu_llc_id for AMD Fam17h systems Borislav Petkov <bp@suse.de> - 2016-11-08 16:40 +0100
              [tip:x86/urgent] x86/cpu/AMD: Fix cpu_llc_id for AMD Fam17h systems tip-bot for Yazen Ghannam <tipbot@zytor.com> - 2016-11-09 17:20 +0100

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