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=-5.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 11847C433E0 for ; Mon, 22 Feb 2021 12:05:40 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 AC94C64E24 for ; Mon, 22 Feb 2021 12:05:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org AC94C64E24 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+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=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type: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=n8xeeJCjTufJ9cO7b4Q3U7e1vwQGhPdH1D84bVYaaeE=; b=SiVjnrFRPgITcVWPmRVwUXW/z 4c9E4Jw3GedCWMMOGkMvAy20lwayMxLNa3VrLbV8agKEMDXfofkegKhsJD4+esxOfyAn9IehkQUsr 4g4GsuoSGF4dfSm4axb/GJMyqGEUutY/KwAO/i5tdCsNT3RpLy+XWGfQxcvOqvJxP5rVkOlJbO+fh yjMdn3WklPvOB45BHr787OqCQKDTX9Hrgt86GF0TLO3/1F5CD2Hs7yvt/qF16N30Sg9avO8u7Uhrm waUXfGtOAIdsJjds0dYhUxbcTk8U/0OZGDo5P94RsDmD8lL970Hp5uVBt/UfS4Q+CxRpjtXFId+Zo p/Yjd7SBA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1lE9wd-0000tt-FG; Mon, 22 Feb 2021 12:04:07 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1lE9wZ-0000sl-2D for linux-arm-kernel@lists.infradead.org; Mon, 22 Feb 2021 12:04:04 +0000 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 699E71FB; Mon, 22 Feb 2021 04:03:55 -0800 (PST) Received: from [10.37.8.9] (unknown [10.37.8.9]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6D31F3F70D; Mon, 22 Feb 2021 04:03:53 -0800 (PST) Subject: Re: [PATCH v13 4/7] arm64: mte: Enable TCO in functions that can read beyond buffer limits To: Catalin Marinas References: <20210211153353.29094-1-vincenzo.frascino@arm.com> <20210211153353.29094-5-vincenzo.frascino@arm.com> <20210212172128.GE7718@arm.com> From: Vincenzo Frascino Message-ID: Date: Mon, 22 Feb 2021 12:08:07 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210212172128.GE7718@arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210222_070403_212021_805F718C X-CRM114-Status: GOOD ( 20.04 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Branislav Rankov , Marco Elver , Lorenzo Pieralisi , Andrey Konovalov , Evgenii Stepanov , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Alexander Potapenko , linux-arm-kernel@lists.infradead.org, Andrey Ryabinin , Andrew Morton , Will Deacon , Dmitry Vyukov Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2/12/21 5:21 PM, Catalin Marinas wrote: >> + >> + /* >> + * This function is called on each active smp core at boot >> + * time, hence we do not need to take cpu_hotplug_lock again. >> + */ >> + static_branch_enable_cpuslocked(&mte_async_mode); >> } > Sorry, I missed the cpuslocked aspect before. Is there any reason you > need to use this API here? I suggested to add it to the > mte_enable_kernel_sync() because kasan may at some point do this > dynamically at run-time, so the boot-time argument doesn't hold. But > it's also incorrect as this function will be called for hot-plugged > CPUs as well after boot. > > The only reason for static_branch_*_cpuslocked() is if it's called from > a region that already invoked cpus_read_lock() which I don't think is > the case here. I agree with your analysis on why static_branch_*_cpuslocked() is needed, in fact cpus_read_lock() takes cpu_hotplug_lock as per comment on top of the line of code. If I try to take that lock when enabling the secondary cores I end up in the situation below: [ 0.283402] smp: Bringing up secondary CPUs ... .... [ 5.890963] Call trace: [ 5.891050] dump_backtrace+0x0/0x19c [ 5.891212] show_stack+0x18/0x70 [ 5.891373] dump_stack+0xd0/0x12c [ 5.891531] dequeue_task_idle+0x28/0x40 [ 5.891686] __schedule+0x45c/0x6c0 [ 5.891851] schedule+0x70/0x104 [ 5.892010] percpu_rwsem_wait+0xe8/0x104 [ 5.892174] __percpu_down_read+0x5c/0x90 [ 5.892332] percpu_down_read.constprop.0+0xbc/0xd4 [ 5.892497] cpus_read_lock+0x10/0x1c [ 5.892660] static_key_enable+0x18/0x3c [ 5.892823] mte_enable_kernel_async+0x40/0x70 [ 5.892988] kasan_init_hw_tags_cpu+0x50/0x60 [ 5.893144] cpu_enable_mte+0x24/0x70 [ 5.893304] verify_local_cpu_caps+0x58/0x120 [ 5.893465] check_local_cpu_capabilities+0x18/0x1f0 [ 5.893626] secondary_start_kernel+0xe0/0x190 [ 5.893790] 0x0 [ 5.893975] bad: scheduling from the idle thread! [ 5.894065] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G W 5.11.0-rc7-10587-g22cd50bcfcf-dirty #6 and the kernel panics. Note: there is a look of msg drop in between enabling the secondary and the first clean stack trace. -- Regards, Vincenzo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel