From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 055A8C47256 for ; Tue, 5 May 2020 06:51:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DDD112075A for ; Tue, 5 May 2020 06:51:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728171AbgEEGvP (ORCPT ); Tue, 5 May 2020 02:51:15 -0400 Received: from foss.arm.com ([217.140.110.172]:60766 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725320AbgEEGvP (ORCPT ); Tue, 5 May 2020 02:51:15 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CCD061FB; Mon, 4 May 2020 23:51:14 -0700 (PDT) Received: from [10.163.71.248] (unknown [10.163.71.248]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6AD753F68F; Mon, 4 May 2020 23:51:12 -0700 (PDT) Subject: Re: [PATCH V3 02/16] arm64/cpufeature: Drop TraceFilt feature exposure from ID_DFR0 register To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, Catalin Marinas , Marc Zyngier , Mark Rutland , James Morse , Suzuki K Poulose , linux-kernel@vger.kernel.org References: <1588426445-24344-1-git-send-email-anshuman.khandual@arm.com> <1588426445-24344-3-git-send-email-anshuman.khandual@arm.com> <20200504202453.GA5012@willie-the-truck> From: Anshuman Khandual Message-ID: <56cd3062-a0c2-6cdf-b7c6-c2b7bf56d23b@arm.com> Date: Tue, 5 May 2020 12:20:41 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200504202453.GA5012@willie-the-truck> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/05/2020 01:54 AM, Will Deacon wrote: > On Sat, May 02, 2020 at 07:03:51PM +0530, Anshuman Khandual wrote: >> ID_DFR0 based TraceFilt feature should not be exposed to guests. Hence lets >> drop it. >> >> Cc: Catalin Marinas >> Cc: Will Deacon >> Cc: Marc Zyngier >> Cc: Mark Rutland >> Cc: James Morse >> Cc: Suzuki K Poulose >> Cc: linux-arm-kernel@lists.infradead.org >> Cc: linux-kernel@vger.kernel.org >> >> Suggested-by: Mark Rutland >> Reviewed-by: Suzuki K Poulose >> Signed-off-by: Anshuman Khandual >> --- >> arch/arm64/kernel/cpufeature.c | 1 - >> 1 file changed, 1 deletion(-) >> >> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c >> index 6d032fbe416f..51386dade423 100644 >> --- a/arch/arm64/kernel/cpufeature.c >> +++ b/arch/arm64/kernel/cpufeature.c >> @@ -435,7 +435,6 @@ static const struct arm64_ftr_bits ftr_id_pfr1[] = { >> }; >> >> static const struct arm64_ftr_bits ftr_id_dfr0[] = { >> - ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 28, 4, 0), > > Hmm, this still confuses me. Is this not now FTR_NONSTRICT? Why is that ok? Mark had mentioned about it earlier (https://patchwork.kernel.org/patch/11287805/) Did I misinterpret the first part ? Could not figure "capping the emulated debug features" part. Probably, Mark could give some more details. >From the earlier discussion: * ID_DFR0 fields need more thought; we should limit what we expose here. I don't think it's valid for us to expose TraceFilt, and I suspect we need to add capping for debug features we currently emulate.