From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751645AbdC0Q6C (ORCPT ); Mon, 27 Mar 2017 12:58:02 -0400 Received: from mail.skyhub.de ([5.9.137.197]:35814 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751302AbdC0Q5z (ORCPT ); Mon, 27 Mar 2017 12:57:55 -0400 Date: Mon, 27 Mar 2017 18:57:10 +0200 From: Borislav Petkov To: kan.liang@intel.com Cc: peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, linux-kernel@vger.kernel.org, acme@kernel.org, eranian@google.com, jolsa@kernel.org, ak@linux.intel.com Subject: Re: [PATCH V2 1/2] x86/msr: add msr_set/clear_bit_on_cpu/cpus access functions Message-ID: <20170327165710.zvqa7y7e6adby5bc@pd.tnic> References: <1490629658-4308-1-git-send-email-kan.liang@intel.com> <1490629658-4308-2-git-send-email-kan.liang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1490629658-4308-2-git-send-email-kan.liang@intel.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 27, 2017 at 08:47:37AM -0700, kan.liang@intel.com wrote: > From: Kan Liang > > Having msr_set/clear_bit on many cpus or given CPU can avoid extra > unnecessory IPIs How does that happen? You have smp_call_function_many() sending IPIs to each CPU in the mask. Doesn't look like avoiding anything to me. Now if you want to have interfaces set/clear_bit_on_cpu(s), that's a different story. And those actually double the amount of IPIs the moment you do a read-modify-write operation on the MSR, i.e., you want to read *and* write afterwards. If you only want to do a single operation - set or clear - like you're doing in your other patch, then I guess that's fine as it wraps the smp_call_function* boilerplate code. > and simplify MSR content manipulation, when it only > needs to flip a bit. > There is already msr_set/clear_bit, but missing the _on_cpu and _on_cpus > version. > > Signed-off-by: Kan Liang > --- > arch/x86/include/asm/msr.h | 29 ++++++++++++++++++ > arch/x86/lib/msr-smp.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 105 insertions(+) > > diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h > index 898dba2..9bc999b 100644 > --- a/arch/x86/include/asm/msr.h > +++ b/arch/x86/include/asm/msr.h > @@ -20,6 +20,11 @@ struct msr { > }; > }; > > +struct msr_bit_info { > + u32 msr_no; > + u8 bit; > +}; No, not *another* struct msr*info. Please reuse msr_info. -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.