Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752015AbdGZOSY (ORCPT ); Wed, 26 Jul 2017 10:18:24 -0400 Received: from mx2.suse.de ([195.135.220.15]:45873 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751210AbdGZOSU (ORCPT ); Wed, 26 Jul 2017 10:18:20 -0400 Date: Wed, 26 Jul 2017 16:17:36 +0200 From: Borislav Petkov To: Suravee Suthikulpanit Cc: linux-kernel@vger.kernel.org, x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, peterz@infradead.org, Yazen.Ghannam@amd.com Subject: Re: [PATCH] x86/amd: Only fixup cpu_core_id for pre-family17h Message-ID: <20170726141736.GC30471@nazgul.tnic> References: <1501009980-2273-1-git-send-email-suravee.suthikulpanit@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1501009980-2273-1-git-send-email-suravee.suthikulpanit@amd.com> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3176 Lines: 115 On Tue, Jul 25, 2017 at 02:13:00PM -0500, Suravee Suthikulpanit wrote: > Current fixup causes cpu_core_id for family17 w/ downcore configuration > to be incorrect as shown here: Applied but did some heavy massaging: --- From: Suravee Suthikulpanit Date: Tue, 25 Jul 2017 14:13:00 -0500 Subject: [PATCH] x86/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 Cc: Yazen Ghannam Cc: x86-ml Link: http://lkml.kernel.org/r/1501009980-2273-1-git-send-email-suravee.suthikulpanit@amd.com [ Heavily massaged. ] Signed-off-by: --- 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 110ca5d2bb87..aa3cf163fd19 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -297,6 +297,22 @@ 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 @@ -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 -- 2.14.0.rc0 SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --