From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755914AbeCHNn4 (ORCPT ); Thu, 8 Mar 2018 08:43:56 -0500 Received: from foss.arm.com ([217.140.101.70]:38176 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755892AbeCHNnz (ORCPT ); Thu, 8 Mar 2018 08:43:55 -0500 Date: Thu, 8 Mar 2018 13:43:50 +0000 From: Dave Martin To: Suzuki K Poulose Cc: mark.rutland@arm.com, ckadabi@codeaurora.org, ard.biesheuvel@linaro.org, marc.zyngier@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, jnair@caviumnetworks.com, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v3 15/22] arm64: capabilities: Change scope of VHE to Boot CPU feature Message-ID: <20180308134348.GP32331@e103592.cambridge.arm.com> References: <20180209175513.17100-1-suzuki.poulose@arm.com> <20180209175513.17100-30-suzuki.poulose@arm.com> <20180212171727.GL5862@e103592.cambridge.arm.com> <25d774db-0ebd-b06d-20b5-5e31ede58fa3@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <25d774db-0ebd-b06d-20b5-5e31ede58fa3@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, Mar 08, 2018 at 12:10:22PM +0000, Suzuki K Poulose wrote: > On 12/02/18 17:17, Dave Martin wrote: > >On Fri, Feb 09, 2018 at 05:54:59PM +0000, Suzuki K Poulose wrote: > >>We expect all CPUs to be running at the same EL inside the kernel > >>with or without VHE enabled and we have strict checks to ensure > >>that any mismatch triggers a kernel panic. If VHE is enabled, > >>we use the feature based on the boot CPU and all other CPUs > >>should follow. This makes it a perfect candidate for a cpability > > > >capability > > > >>based on the boot CPU, which should be matched by all the CPUs > >>(both when is ON and OFF). This saves us some not-so-pretty > >>hooks and special code, just for verifying the conflict. > >> > >>Cc: Marc Zyngier > >>Cc: Dave Martin > >>Cc: Will Deacon > >>Signed-off-by: Suzuki K Poulose > >>--- > >> arch/arm64/include/asm/cpufeature.h | 7 +++++++ > >> arch/arm64/include/asm/virt.h | 6 ------ > >> arch/arm64/kernel/cpufeature.c | 5 +++-- > >> arch/arm64/kernel/smp.c | 38 ------------------------------------- > >> 4 files changed, 10 insertions(+), 46 deletions(-) > >> > >>diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h > >>index 5f56a8342065..dfce93f79ae7 100644 > >>--- a/arch/arm64/include/asm/cpufeature.h > >>+++ b/arch/arm64/include/asm/cpufeature.h > >>@@ -276,6 +276,13 @@ extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; > >> (ARM64_CPUCAP_SCOPE_LOCAL_CPU | \ > >> ARM64_CPUCAP_OPTIONAL_FOR_LATE_CPU) > >>+/* > >>+ * Critical CPU feature used early in the boot based on the boot CPU. > >>+ * The feature should be matched by all booting CPU (both miss and hit > >>+ * cases). > >>+ */ > >>+#define ARM64_CPUCAP_CRITICAL_BOOT_CPU_FEATURE ARM64_CPUCAP_SCOPE_BOOT_CPU > >>+ > > > >Nit: would it be consistent with the uses we already have for the word > >"strict" to use that word here? i.e., > >ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE. > >Or do you think that would be more confusing? > > We don't use the "STRICT" tag anymore. Moreover, I used CRITICAL to indicate > that it is special in a way that all the "late" CPUs (in this case all > secondaries) should match the "state" of the capability (i.e, both ON and OFF) > as that of the boot CPU. I am OK to change it to STRICT. OK, I think so long as the definition is clear the precise name doesn't matter too much. I suggest deleting "critical" from the comment though, since that suggests a circular definition. The meaning seems clear(er) without it. [...] Cheers ---Dave