Commit-ID:  b89b41d0b8414690ec0030c134b8bde209e6d06c
Gitweb:     http://git.kernel.org/tip/b89b41d0b8414690ec0030c134b8bde209e6d06c
Author:     Suravee Suthikulpanit <suravee.suthikulpa...@amd.com>
AuthorDate: Mon, 31 Jul 2017 10:51:58 +0200
Committer:  Ingo Molnar <mi...@kernel.org>
CommitDate: Thu, 10 Aug 2017 17:37:43 +0200

x86/cpu/amd: Limit cpu_core_id fixup to families older than F17h

Current cpu_core_id fixup causes downcored F17h configurations to be
incorrect:

  NODE: 0
  processor  0 core id : 0
  processor  1 core id : 1
  processor  2 core id : 2
  processor  3 core id : 4
  processor  4 core id : 5
  processor  5 core id : 0

  NODE: 1
  processor  6 core id : 2
  processor  7 core id : 3
  processor  8 core id : 4
  processor  9 core id : 0
  processor 10 core id : 1
  processor 11 core id : 2

Code that relies on the cpu_core_id, like match_smt(), for example,
which builds the thread siblings masks used by the scheduler, is
mislead.

So, limit the fixup to pre-F17h machines. The new value for cpu_core_id
for F17h and later will represent the CPUID_Fn8000001E_EBX[CoreId],
which is guaranteed to be unique for each core within a socket.

This way we have:

  NODE: 0
  processor  0 core id : 0
  processor  1 core id : 1
  processor  2 core id : 2
  processor  3 core id : 4
  processor  4 core id : 5
  processor  5 core id : 6

  NODE: 1
  processor  6 core id : 8
  processor  7 core id : 9
  processor  8 core id : 10
  processor  9 core id : 12
  processor 10 core id : 13
  processor 11 core id : 14

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpa...@amd.com>
[ Heavily massaged. ]
Signed-off-by: Borislav Petkov <b...@suse.de>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Yazen Ghannam <yazen.ghan...@amd.com>
Link: http://lkml.kernel.org/r/20170731085159.9455-2...@alien8.de
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
 arch/x86/kernel/cpu/amd.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 3b9e220..82d571c 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -298,6 +298,22 @@ static int nearby_node(int apicid)
 #endif
 
 /*
+ * Fix up cpu_core_id for pre-F17h systems to be in the
+ * [0 .. cores_per_node - 1] range. Not really needed but
+ * kept so as not to break existing setups.
+ */
+static void legacy_fixup_core_id(struct cpuinfo_x86 *c)
+{
+       u32 cus_per_node;
+
+       if (c->x86 >= 0x17)
+               return;
+
+       cus_per_node = c->x86_max_cores / nodes_per_socket;
+       c->cpu_core_id %= cus_per_node;
+}
+
+/*
  * Fixup core topology information for
  * (1) AMD multi-node processors
  *     Assumption: Number of cores in each internal node is the same.
@@ -354,15 +370,9 @@ static void amd_get_topology(struct cpuinfo_x86 *c)
        } else
                return;
 
-       /* fixup multi-node processor information */
        if (nodes_per_socket > 1) {
-               u32 cus_per_node;
-
                set_cpu_cap(c, X86_FEATURE_AMD_DCM);
-               cus_per_node = c->x86_max_cores / nodes_per_socket;
-
-               /* core id has to be in the [0 .. cores_per_node - 1] range */
-               c->cpu_core_id %= cus_per_node;
+               legacy_fixup_core_id(c);
        }
 }
 #endif

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