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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 F2CCBC43387 for ; Fri, 18 Jan 2019 16:31:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C9D3520850 for ; Fri, 18 Jan 2019 16:31:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728231AbfARQbD (ORCPT ); Fri, 18 Jan 2019 11:31:03 -0500 Received: from foss.arm.com ([217.140.101.70]:33502 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727346AbfARQbC (ORCPT ); Fri, 18 Jan 2019 11:31:02 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0BB4BEBD; Fri, 18 Jan 2019 08:31:02 -0800 (PST) Received: from [192.168.100.241] (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C0E593F557; Fri, 18 Jan 2019 08:31:00 -0800 (PST) Subject: Re: [PATCH v3 1/7] sysfs/cpu: Allow individual architectures to select vulnerabilities To: Greg KH , Suzuki K Poulose Cc: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will.deacon@arm.com, marc.zyngier@arm.com, dave.martin@arm.com, shankerd@codeaurora.org, linux-kernel@vger.kernel.org, ykaukab@suse.de, julien.thierry@arm.com, mlangsdo@redhat.com, Steven.Price@arm.com, stefan.wahren@i2se.com, rafael@kernel.org, tglx@linutronix.de, jpoimboe@redhat.com, konrad.wilk@oracle.com, mingo@kernel.org, longman@redhat.com, ak@linux.intel.com, jkosina@suse.cz References: <20190109235544.2992426-1-jeremy.linton@arm.com> <20190109235544.2992426-2-jeremy.linton@arm.com> <901f2f29-aa06-13ad-1995-f9f22184e39d@arm.com> <20190118154637.GA8564@kroah.com> From: Jeremy Linton Message-ID: <988ddbc9-ae46-22cc-4228-5f1ea98605c1@arm.com> Date: Fri, 18 Jan 2019 10:31:00 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20190118154637.GA8564@kroah.com> Content-Type: text/plain; charset=utf-8; format=flowed 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 01/18/2019 09:46 AM, Greg KH wrote: > On Mon, Jan 14, 2019 at 10:02:21AM +0000, Suzuki K Poulose wrote: >> >> >> On 09/01/2019 23:55, Jeremy Linton wrote: >>> As suggested on the list, https://lkml.org/lkml/2019/1/4/282, there are >>> a number of cases where its useful for a system to avoid exporting a >>> sysfs entry for a given vulnerability. This set adds an architecture >>> specific callback which returns the bitmap of vulnerabilities the >>> architecture would like to advertise. >>> >>> Signed-off-by: Jeremy Linton >>> Cc: Greg Kroah-Hartman >>> Cc: Rafael J. Wysocki >>> Cc: Thomas Gleixner >>> Cc: Josh Poimboeuf >>> Cc: Konrad Rzeszutek Wilk >>> Cc: Ingo Molnar >>> Cc: Waiman Long >>> Cc: Andi Kleen >>> Cc: Jiri Kosina >>> --- >>> drivers/base/cpu.c | 19 +++++++++++++++++++ >>> include/linux/cpu.h | 7 +++++++ >>> 2 files changed, 26 insertions(+) >>> >>> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c >>> index eb9443d5bae1..35f6dfb24cd6 100644 >>> --- a/drivers/base/cpu.c >>> +++ b/drivers/base/cpu.c >>> @@ -561,6 +561,11 @@ static struct attribute *cpu_root_vulnerabilities_attrs[] = { >>> NULL >>> }; >>> +uint __weak arch_supported_vuln_attr_fields(void) >>> +{ >>> + return VULN_MELTDOWN|VULN_SPECTREV1|VULN_SPECTREV2|VULN_SSB|VULN_L1TF; >>> +} >>> + >>> static const struct attribute_group cpu_root_vulnerabilities_group = { >>> .name = "vulnerabilities", >>> .attrs = cpu_root_vulnerabilities_attrs, >>> @@ -568,6 +573,20 @@ static const struct attribute_group cpu_root_vulnerabilities_group = { >>> static void __init cpu_register_vulnerabilities(void) >>> { >>> + int fld; >>> + int max_fields = ARRAY_SIZE(cpu_root_vulnerabilities_attrs) - 1; >>> + struct attribute **hd = cpu_root_vulnerabilities_attrs; >>> + uint enabled_fields = arch_supported_vuln_attr_fields(); >>> + >>> + /* only enable entries requested by the arch code */ >>> + for (fld = 0; fld < max_fields; fld++) { >>> + if (enabled_fields & 1 << fld) { >>> + *hd = cpu_root_vulnerabilities_attrs[fld]; >>> + hd++; >>> + } >>> + } >>> + *hd = NULL; >>> + >> >> nit: Could we use "is_visible" callback in the attribute group to check this >> dynamically ? > > You should, that is what it is there for. Yes, its a good suggestion. OTOH, I think the plan is to drop this functionality all together by removing the ability to build kernels without the vulnerability checking/processor white lists. That will simplify some of the #ifdef'ing going on as well.