From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752111AbeAPUcK (ORCPT + 1 other); Tue, 16 Jan 2018 15:32:10 -0500 Received: from mail-pf0-f193.google.com ([209.85.192.193]:37780 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751210AbeAPUb4 (ORCPT ); Tue, 16 Jan 2018 15:31:56 -0500 X-Google-Smtp-Source: ACJfBotjqn6BUoE/OJtcBcZAnUoJHtRSeRVCf3fZqkx6kcMyYyrYQsfeRyQqF82oLW6k3s/PLpeZsw== Date: Tue, 16 Jan 2018 12:32:19 -0800 From: Nicolin Chen To: Marc Zyngier Cc: mark.rutland@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, oleg@redhat.com, cdall@linaro.org, tbaicar@codeaurora.org, julien.thierry@arm.com, Dave.Martin@arm.com, robin.murphy@arm.com, james.morse@arm.com, ard.biesheuvel@linaro.org, xiexiuqi@huawei.com, mingo@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC v1] arm64: Handle traps from accessing CNTVCT/CNTFRQ for CONFIG_COMPAT Message-ID: <20180116203218.GA6318@Asurada-Nvidia> References: <1515645816-14063-1-git-send-email-nicoleotsuka@gmail.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 Return-Path: Hello Marc, On Thu, Jan 11, 2018 at 08:51:37AM +0000, Marc Zyngier wrote: > > [ I also added cntfrq here for safety as theoretically it could > > trigger the trap as well. However, my another test case (with > > mrc insturction) doesn't seem to trigger a trap. So I would > > drop it in the next version if someone can confirm it's not > > required. Thanks -- Nicolin ] > > See my previous series on this very subject[1] as well as Will's reply. Thanks for the background. > > - for (hook = sys64_hooks; hook->handler; hook++) > > + for (; hook && hook->handler; hook++) > > if ((hook->esr_mask & esr) == hook->esr_val) { > > hook->handler(esr, regs); > > return; > > > > Also, this code is fairly broken in its handling of conditional > instructions. I understand that it should take care of the condition field as a general instruction handler. Just for curiosity: If we confine the topic to read access of CNTVCT/CNTFRQ, what'd be the penalty by ignoring the condition field and executing it anyway? Thank you Nicolin