From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934000AbbJHPIZ (ORCPT ); Thu, 8 Oct 2015 11:08:25 -0400 Received: from foss.arm.com ([217.140.101.70]:34907 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933554AbbJHPIY (ORCPT ); Thu, 8 Oct 2015 11:08:24 -0400 Date: Thu, 8 Oct 2015 16:08:19 +0100 From: Catalin Marinas To: "Suzuki K. Poulose" Cc: mark.rutland@arm.com, Vladimir.Murzin@arm.com, steve.capper@linaro.org, ard.biesheuvel@linaro.org, marc.zyngier@arm.com, andre.przywara@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, edward.nevill@linaro.org, aph@redhat.com, james.morse@arm.com, dave.martin@arm.com, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 16/22] arm64/debug: Make use of the system wide safe value Message-ID: <20151008150819.GL17192@e104818-lin.cambridge.arm.com> References: <1444064531-25607-1-git-send-email-suzuki.poulose@arm.com> <1444064531-25607-17-git-send-email-suzuki.poulose@arm.com> <20151008111128.GH17192@e104818-lin.cambridge.arm.com> <561659EC.7030508@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <561659EC.7030508@arm.com> 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 Thu, Oct 08, 2015 at 12:56:28PM +0100, Suzuki K. Poulose wrote: > On 08/10/15 12:11, Catalin Marinas wrote: > >On Mon, Oct 05, 2015 at 06:02:05PM +0100, Suzuki K. Poulose wrote: > >>@@ -137,13 +138,17 @@ extern struct pmu perf_ops_bp; > >> /* Determine number of BRP registers available. */ > >> static inline int get_num_brps(void) > >> { > >>- return ((read_cpuid(ID_AA64DFR0_EL1) >> 12) & 0xf) + 1; > >>+ return 1 + > >>+ cpuid_feature_extract_field(read_system_reg(SYS_ID_AA64DFR0_EL1), > >>+ ID_AA64DFR0_BRPS_SHIFT); > >> } > > > >cpuid_feature_extract_field() is fine but we should we bother with > >read_system_reg vs just read_cpuid? > >Similar question for patch 17/22. > > Well, we would have already TAINTed the kernel, if these fields are different. > It is just the matter of, whether we want to provide the safer value on a tainted > kernel or not. I am open to suggestions. Ah, sorry, I mixed read_system_reg() with read_cpu_sysreg(). I think we need to rename the latter as it gets confusing. Maybe something like read_native_sys_reg() or __raw_read_system_reg(). -- Catalin