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=-0.6 required=3.0 tests=DATE_IN_PAST_24_48, DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 6F5F6C67839 for ; Thu, 13 Dec 2018 17:29:41 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 43DC820879 for ; Thu, 13 Dec 2018 17:29:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="HLQ+gfti" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 43DC820879 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=qYMA+h2WjdbZwjddLZrxMKq+NZCqMS0s9bSIFO7XCSs=; b=HLQ+gftiH2VtzDIWZDfzyuuw/ 8aUx2hTp6AE2jOlRcSEmFnuAr690F5GzwIxoOInkYbFUwaWbIzwr7W2CPFeROg8M7ZgNGWZEA3Gdr +laO5GhiFG0oBA9/+s2/KVjNRe92cEaQeBuuSqwX/xyY8TcADU5b5xcT/BmCbvZDs8YQI9AjaRwcS V+xl3cr4UwCjNKd+uB4eC5z/1AOabqBHo4tir7NntMb9LdEccR2fnCPqkD7jcoS1hErJGmwqTGwJc gnYDvu+i/4+Yy4XJLUZsN8aDB3zCkU4EE2sYcYo7UcWnohidvyXNQNXpTBMljT8kJlIjwfNtv9D/0 cXloryyOQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gXUns-0002D8-7Y; Thu, 13 Dec 2018 17:29:40 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gXUno-0002Cd-6H for linux-arm-kernel@lists.infradead.org; Thu, 13 Dec 2018 17:29:37 +0000 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 CDF9EA78; Thu, 13 Dec 2018 09:29:24 -0800 (PST) Received: from [192.168.100.242] (usa-sjc-mx-foss1.foss.arm.com [217.140.101.70]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 38BCC3F575; Thu, 13 Dec 2018 09:29:24 -0800 (PST) Subject: Re: [PATCH 0/6] add system vulnerability sysfs entries To: Dave Martin References: <20181206234408.1287689-1-jeremy.linton@arm.com> <20181213120726.GB3505@e103592.cambridge.arm.com> From: Jeremy Linton Message-ID: <58ce38ff-c347-8cb7-ba79-9eea491e30e8@arm.com> Date: Wed, 12 Dec 2018 09:48:03 -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: <20181213120726.GB3505@e103592.cambridge.arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20181213_092936_235649_5A03FED6 X-CRM114-Status: GOOD ( 27.27 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, suzuki.poulose@arm.com, marc.zyngier@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, shankerd@codeaurora.org, ykaukab@suse.de, linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Dave, Thanks for looking at this! On 12/13/2018 06:07 AM, Dave Martin wrote: > On Thu, Dec 06, 2018 at 05:44:02PM -0600, Jeremy Linton wrote: >> Part of this series was originally by Mian Yousaf Kaukab. >> >> Arm64 machines should be displaying a human readable >> vulnerability status to speculative execution attacks in >> /sys/devices/system/cpu/vulnerabilities > > Is there any agreement on the strings that will be returned in there? > > A quick search didn't find anything obvious upstream. There is > documentation proposed in [1], but I don't know what happened to it and > it doesn't define the mitigation strings at all. (I didn't follow the > discussion, so there is likely background here I'm not aware of.) > > If the mitigation strings are meaningful at all, they really ought to be > documented somewhere since this is ABI. I think they are in testing? But that documentation is missing the "Unknown" state which tends to be our default case for "we don't have a complete white/black list", or "mitigation disabled, we don't know if your vulnerable", etc. I'm not sure I like the "Unknown" state, but we can try to add it to the documentation. > >> This series enables that behavior by providing the expected >> functions. Those functions expose the cpu errata and feature >> states, as well as whether firmware is responding appropriately >> to display the overall machine status. This means that in a >> heterogeneous machine we will only claim the machine is mitigated >> or safe if we are confident all booted cores are safe or >> mitigated. Otherwise, we will display unknown or unsafe >> depending on how much of the machine configuration can >> be assured. > > Can the vulnerability status change once we enter userspace? Generally no, for heterogeneous machines I think the answer here is yes, a user could check the state, and have it read "Not affected" then bring another core online which causes the state to change at which point if they re-read /sys it may reflect another state. OTOH, given that we tend to default to mitigated usually this shouldn't be an issue unless someone has disabled the mitigation. > > I see no locking or other concurrency protections, and various global > variables that could be __ro_after_init if nothing will change them > after boot. I think the state changes are all protected due to the fact the bringing a core online/offline is serialized. > > If they can change after boot, userspace has no way to be notified, Is checking on hotplug notification sufficient? > > (I haven't grokked the patches fully, so the answer to this question may > be reasonably straightforward...) > > > Cheers > ---Dave > > [1] https://lkml.org/lkml/2018/1/8/145 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel