From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756139AbeDZN2q (ORCPT ); Thu, 26 Apr 2018 09:28:46 -0400 Received: from mx2.suse.de ([195.135.220.15]:38144 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755172AbeDZN2p (ORCPT ); Thu, 26 Apr 2018 09:28:45 -0400 Date: Thu, 26 Apr 2018 15:28:29 +0200 From: Borislav Petkov To: Yazen Ghannam Cc: x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] x86/smpboot: Don't do mwait_play_dead() on AMD systems Message-ID: <20180426132829.GK15043@pd.tnic> References: <20180403140228.58540-1-Yazen.Ghannam@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180403140228.58540-1-Yazen.Ghannam@amd.com> User-Agent: Mutt/1.9.3 (2018-01-21) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 03, 2018 at 09:02:28AM -0500, Yazen Ghannam wrote: > From: Yazen Ghannam > > Recent AMD systems support using MWAIT for C1 state. However, MWAIT will > not allow deeper cstates than C1 on current systems. > > With play_dead() we expect the OS to use the deepest state available. > The deepest state available on AMD systems is reached through SystemIO > or HALT. If MWAIT is available, we use it instead of the other methods, > so we never reach the deepest state. > > Don't try to use MWAIT to play_dead() on AMD systems. Instead, we'll use > CPUIDLE to enter the deepest state advertised by firmware. If CPUIDLE is > not available then we fallback to HALT. > > Signed-off-by: Yazen Ghannam > --- > Link: > https://lkml.kernel.org/r/20180402183424.48222-1-Yazen.Ghannam@amd.com > > v1->v2: > * Drop comment in code. > > arch/x86/kernel/smpboot.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c > index ff99e2b6fc54..12599e55e040 100644 > --- a/arch/x86/kernel/smpboot.c > +++ b/arch/x86/kernel/smpboot.c > @@ -1536,6 +1536,8 @@ static inline void mwait_play_dead(void) > void *mwait_ptr; > int i; > > + if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) > + return; > if (!this_cpu_has(X86_FEATURE_MWAIT)) > return; > if (!this_cpu_has(X86_FEATURE_CLFLUSH)) > -- Reviewed-by: Borislav Petkov -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --