Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754168AbbGQUwh (ORCPT ); Fri, 17 Jul 2015 16:52:37 -0400 Received: from one.firstfloor.org ([193.170.194.197]:44535 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752546AbbGQUwg (ORCPT ); Fri, 17 Jul 2015 16:52:36 -0400 Date: Fri, 17 Jul 2015 22:52:33 +0200 From: Andi Kleen To: Stephane Eranian Cc: Andi Kleen , Andi Kleen , Peter Zijlstra , LKML Subject: Re: [PATCH 3/3] x86, perf: Add PEBS frontend profiling for Skylake Message-ID: <20150717205233.GJ1747@two.firstfloor.org> References: <1435612935-24425-1-git-send-email-andi@firstfloor.org> <1435612935-24425-3-git-send-email-andi@firstfloor.org> <20150717200900.GE7380@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1383 Lines: 33 On Fri, Jul 17, 2015 at 01:41:04PM -0700, Stephane Eranian wrote: > Andi, > > On Fri, Jul 17, 2015 at 1:09 PM, Andi Kleen wrote: > >> I believe this mask of 0x3fff17 is wrong and should instead be > >> 0x7fffff based on the description of the FRONTEND > >> MSR I see in the SDM Table 18-54 (bit 0-22 are valid). Otherwise, some > >> valid latency values may be rejected. > > > > No, my mask is correct. > > > Ok, so your event mask (0x17) really only allows what's defined > instead the full width of the field. > > As for the IDQ_BUBBLE_WIDTH, you only allow 2 bits out of 3, so > maximum bubble threshold is 3 > instead of 7. I assume this is because you know that it cannot have > more than 3 simultaneously then. > > Would be good to explain this a bit more in the code. I don't think the code is the right place to document such registers. I can ask for the SDM to be clarified. But if you follow the documented events you will never set any undefined bits, so you won't need to care about this. We just have to exclude it at the kernel level to avoid #GP crashes if someone is writing random values. -Andi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/