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=-2.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED 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 50F48C282C0 for ; Wed, 23 Jan 2019 18:40:21 +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 1BFA121872 for ; Wed, 23 Jan 2019 18:40:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="cn4EhRnm" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1BFA121872 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-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=B8+Y4thNCWPJGA/KwIQu0/xJXjrbZOG7jFg+qvugRrI=; b=cn4EhRnmuk24t3 LcaAmgMc16ITM774EGE+RGfj9fFzvcRxDL/m4SGQTAQVm+wrEhet8SU7/LmzPjOjBc74f2VaeQbki rZsb/pM9RJN2nC9/9/zlxf+EyhtbUIBimXAlqQDbMrUkh4zp4NBASh/gg6Wn80RAA7GC+oUE63WoU mSe8DnJhrC/mS0ZGLoafhu3i1pYx41FM+uP1xFD6/0QeStISCvkGJUVba5uvD9h3+KEWzPcScwT7s vP5XPqj0dZ9vyZnQ+nZensJCxD5K5RTJBBCESfCfa7mBJRlICy35dYfh58M6NriwlJ/sHuZP0dmsw V6Crl2Dy4ZNZ3DT/JeIQ==; 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 1gmNRg-0003ey-Jg; Wed, 23 Jan 2019 18:40:16 +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 1gmNRd-0003eR-Ps for linux-arm-kernel@lists.infradead.org; Wed, 23 Jan 2019 18:40:15 +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 1258FEBD; Wed, 23 Jan 2019 10:40:13 -0800 (PST) Received: from [10.1.196.105] (eglon.cambridge.arm.com [10.1.196.105]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1A0F23F237; Wed, 23 Jan 2019 10:40:09 -0800 (PST) Subject: Re: [PATCH v7 22/25] ACPI / APEI: Kick the memory_failure() queue for synchronous errors To: Borislav Petkov References: <20181203180613.228133-1-james.morse@arm.com> <20181203180613.228133-23-james.morse@arm.com> <20190121175850.GO29166@zn.tnic> From: James Morse Message-ID: <58053f17-5f03-8408-7252-a38ed3d448a9@arm.com> Date: Wed, 23 Jan 2019 18:40:08 +0000 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190121175850.GO29166@zn.tnic> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190123_104013_854782_F3264609 X-CRM114-Status: GOOD ( 26.60 ) 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: Rafael Wysocki , Tony Luck , Fan Wu , linux-mm@kvack.org, Marc Zyngier , Catalin Marinas , Xie XiuQi , Will Deacon , Christoffer Dall , Dongjiu Geng , linux-acpi@vger.kernel.org, Naoya Horiguchi , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, Len Brown Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Boris, On 21/01/2019 17:58, Borislav Petkov wrote: > On Mon, Dec 03, 2018 at 06:06:10PM +0000, James Morse wrote: >> memory_failure() offlines or repairs pages of memory that have been >> discovered to be corrupt. These may be detected by an external >> component, (e.g. the memory controller), and notified via an IRQ. >> In this case the work is queued as not all of memory_failure()s work >> can happen in IRQ context. >> >> If the error was detected as a result of user-space accessing a >> corrupt memory location the CPU may take an abort instead. On arm64 >> this is a 'synchronous external abort', and on a firmware first >> system it is replayed using NOTIFY_SEA. >> >> This notification has NMI like properties, (it can interrupt >> IRQ-masked code), so the memory_failure() work is queued. If we >> return to user-space before the queued memory_failure() work is >> processed, we will take the fault again. This loop may cause platform >> firmware to exceed some threshold and reboot when Linux could have >> recovered from this error. >> >> If a ghes notification type indicates that it may be triggered again >> when we return to user-space, use the task-work and notify-resume >> hooks to kick the relevant memory_failure() queue before returning >> to user-space. >> --- >> I assume that if NOTIFY_NMI is coming from SMM it must suffer from >> this problem too. > > Good question. > > I'm guessing all those things should be queued on a normal struct > work_struct queue, no? ghes_notify_nmi() does this today with its: | irq_work_queue(&ghes_proc_irq_work); Once its in IRQ context, the irq_work pokes memory_failure_queue(), which schedule_work_on()s. Finally we schedule() in process context, and can unmap the affected memory. The problem is between each of these steps we might return to user-space and run the instruction that tripped all this to begin with. My SMM comment was because the CPU must jump from user-space->SMM, which injects an NMI into the kernel. The kernel's EIP must point into user-space, so returning from the NMI without doing the memory_failure() work puts us back the same position we started in. > Now, memory_failure_queue() does that and can run from IRQ context so > you need only an irq_work which can queue from NMI context. We do it > this way in the MCA code: > (was there something missing here?) > We queue in an irq_work in NMI context and work through the items in > process context. How are you getting from NMI to process context in one go? This patch causes the IRQ->process transition. The arch specific bit of this gives the irq work queue a kick if returning from the NMI would unmask IRQs. This makes it look like we moved from NMI to IRQ context without returning to user-space. Once ghes_handle_memory_failure() runs in IRQ context, it task_work_add()s the call to ghes_kick_memory_failure(). Finally on the way out of the kernel to user-space that task_work runs and the memory_failure() work happens in process context. During all this the user-space program counter can point at a poisoned location, but we don't return there until the memory_failure() work has been done. >> @@ -407,7 +447,22 @@ static void ghes_handle_memory_failure(struct acpi_hest_generic_data *gdata, int >> >> if (flags != -1) >> memory_failure_queue(pfn, flags); >> -#endif >> + >> + /* >> + * If the notification indicates that it was the interrupted >> + * instruction that caused the error, try to kick the >> + * memory_failure() queue before returning to user-space. >> + */ >> + if (ghes_is_synchronous(ghes) && current->mm != &init_mm) { >> + callback = kzalloc(sizeof(*callback), GFP_ATOMIC); > > Can we avoid that GFP_ATOMIC allocation and kfree() in > ghes_kick_memory_failure()? > > I mean, that struct ghes_memory_failure_work is small enough and we > already do lockless allocation: > > estatus_node = (void *)gen_pool_alloc(ghes_estatus_pool, node_len); > > so I guess we could add that ghes_memory_failure_work struct to that > estatus_node, hand it into ghes_do_proc() and then free it. I forget estatus_node is a linux thing, not an ACPI-spec thing! Hmmm, ghes_handle_memory_failure() runs for POLLED and irq error sources too, they don't have an estatus_node. We don't care about this ret_to_user() problem as they are all asynchronous, this is why we have ghes_is_synchronous()... It feels like there should be a way to do this, let me have a go... Thanks, James _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel