From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756952AbdEKPjL (ORCPT ); Thu, 11 May 2017 11:39:11 -0400 Received: from foss.arm.com ([217.140.101.70]:49760 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752345AbdEKPhy (ORCPT ); Thu, 11 May 2017 11:37:54 -0400 Date: Thu, 11 May 2017 16:37:20 +0100 From: Mark Rutland To: Suzuki K Poulose , marc.zyngier@arm.com Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, bigeasy@linutronix.de, catalin.marinas@arm.com, peterz@infradead.org, tglx@linutronix.de, will.deacon@arm.com Subject: Re: [PATCHv2] arm64/cpufeature: don't use mutex in bringup path Message-ID: <20170511153719.GB19626@leverpostej> References: <1494514878-26878-1-git-send-email-mark.rutland@arm.com> <498b2e16-538a-d5ea-7843-2ebbff2007df@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <498b2e16-538a-d5ea-7843-2ebbff2007df@arm.com> 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 On Thu, May 11, 2017 at 04:15:38PM +0100, Suzuki K Poulose wrote: > On 11/05/17 16:01, Mark Rutland wrote: > >+static inline bool cpus_have_const_cap(int num) > >+{ > >+ if (static_branch_likely(&arm64_const_caps_ready)) > >+ return __cpus_have_const_cap(num); > >+ else > >+ return cpus_have_cap(num); > > We use cpus_have_const_cap() from hyp code, via has_vhe() and we could potentially > try to access unmapped kernel data from hyp if we fallback to cpus_have_cap(). > However, it looks like we have already set arm64_const_caps_ready, so should not > hit it in practise. May be we could add a stricter version of the helper ? > > static inline cpus_have_const_cap_strict(int num) > { > BUG_ON(!static_branch_likely(&arm64_const_caps_ready); > return __cpus_have_const_cap(num); > } Just to check, is that the only user of cpus_have_const_cap() at hyp? If so, I can do something like the above, patching to use it for has_vhe(). We don't have a BUG handler at hyp, but that should trigger a hyp panic, which I guess is good enough. Marc, thoughts? Thanks, Mark.