Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751888AbaJSVfh (ORCPT ); Sun, 19 Oct 2014 17:35:37 -0400 Received: from casper.infradead.org ([85.118.1.10]:41960 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751483AbaJSVfg (ORCPT ); Sun, 19 Oct 2014 17:35:36 -0400 Date: Sun, 19 Oct 2014 23:35:34 +0200 From: Peter Zijlstra To: Andy Lutomirski Cc: Valdis Kletnieks , "linux-kernel@vger.kernel.org" , Paul Mackerras , Arnaldo Carvalho de Melo , Ingo Molnar , Kees Cook , Andrea Arcangeli , Erik Bosman Subject: Re: [RFC 5/5] x86,perf: Only allow rdpmc if a perf_event is mapped Message-ID: <20141019213534.GG23531@worktop.programming.kicks-ass.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 16, 2014 at 05:00:56PM -0700, Andy Lutomirski wrote: > The current cap_user_rdpmc code seems rather confused to me. On x86, > *all* events set cap_user_rdpmc if the global rdpmc control is set. > But only x86_pmu events define .event_idx, so amd uncore events won't > actually expose their rdpmc index to userspace. > > Would it make more sense to add a flag PERF_X86_EVENT_RDPMC_PERMITTED > that gets set on all events created while rdpmc == 1, to change > x86_pmu_event_idx to do something like: > > if (event->hw.flags & PERF_X86_EVENT_RDPMC_PERMITTED) > return event->hw.event_base_rdpmc + 1; > else > return 0; > > and to change arch_perf_update_userpage cap_user_rdpmc to match > PERF_X86_EVENT_RDPMC_PERMITTED? > > Then we could ditch the static key and greatly simplify writes to the > rdpmc flag by just counting PERF_X86_EVENT_RDPMC_PERMITTED events. > > This would be a user-visible change on AMD, and I can't test it. I have AMD hardware to test this. But yes something like that seems fine. -- 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/