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