From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754624AbcILSZ0 (ORCPT ); Mon, 12 Sep 2016 14:25:26 -0400 Received: from out4-smtp.messagingengine.com ([66.111.4.28]:42636 "EHLO out4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752063AbcILSZY (ORCPT ); Mon, 12 Sep 2016 14:25:24 -0400 X-Sasl-enc: 2b2WXM3G9b6tMo76jo/TBW1XuNtSmZJbFwYYpiz5qZb9 1473704723 Date: Mon, 12 Sep 2016 15:25:19 -0300 From: Henrique de Moraes Holschuh To: Andi Kleen Cc: Kyle Huey , linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH] prctl,x86 Add PR_[GET|SET]_CPUID for controlling the CPUID instruction. Message-ID: <20160912182519.GA23180@khazad-dum.debian.net> References: <1473640169-24145-1-git-send-email-khuey@kylehuey.com> <87twdl9fz8.fsf@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87twdl9fz8.fsf@tassilo.jf.intel.com> X-GPG-Fingerprint1: 4096R/39CB4807 C467 A717 507B BAFE D3C1 6092 0BD9 E811 39CB 4807 User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 12 Sep 2016, Andi Kleen wrote: > The cpuid char driver does this, other code may too. Such as anything that calls sync_core(). That includes processor hotplug paths, and who knows what else... > You probably would need to protect these CPUIDs with an exception > handler that temporarily disables this bit and retries. Better time that MSR access first. Hopefully, it is fast enough for that. -- Henrique Holschuh