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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B523EC4167B for ; Fri, 1 Dec 2023 05:22:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377374AbjLAFWc (ORCPT ); Fri, 1 Dec 2023 00:22:32 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58058 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229459AbjLAFWa (ORCPT ); Fri, 1 Dec 2023 00:22:30 -0500 Received: from out30-98.freemail.mail.aliyun.com (out30-98.freemail.mail.aliyun.com [115.124.30.98]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A950C10FC; Thu, 30 Nov 2023 21:22:35 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046049;MF=xueshuai@linux.alibaba.com;NM=1;PH=DS;RN=34;SR=0;TI=SMTPD_---0VxVHB4Y_1701408150; Received: from 30.240.114.121(mailfrom:xueshuai@linux.alibaba.com fp:SMTPD_---0VxVHB4Y_1701408150) by smtp.aliyun-inc.com; Fri, 01 Dec 2023 13:22:32 +0800 Message-ID: Date: Fri, 1 Dec 2023 13:22:26 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 1/2] ACPI: APEI: set memory failure flags as MF_ACTION_REQUIRED on synchronous events Content-Language: en-US To: James Morse , rafael@kernel.org, wangkefeng.wang@huawei.com, tanxiaofei@huawei.com, mawupeng1@huawei.com, tony.luck@intel.com, linmiaohe@huawei.com, naoya.horiguchi@nec.com, gregkh@linuxfoundation.org, will@kernel.org, jarkko@kernel.org Cc: linux-acpi@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, linux-edac@vger.kernel.org, acpica-devel@lists.linuxfoundation.org, stable@vger.kernel.org, x86@kernel.org, justin.he@arm.com, ardb@kernel.org, ying.huang@intel.com, ashish.kalra@amd.com, baolin.wang@linux.alibaba.com, bp@alien8.de, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, lenb@kernel.org, hpa@zytor.com, robert.moore@intel.com, lvying6@huawei.com, xiexiuqi@huawei.com, zhuo.song@linux.alibaba.com References: <20221027042445.60108-1-xueshuai@linux.alibaba.com> <20231007072818.58951-2-xueshuai@linux.alibaba.com> From: Shuai Xue In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/12/1 01:39, James Morse wrote: > Hi Shuai, > > On 07/10/2023 08:28, Shuai Xue wrote: >> There are two major types of uncorrected recoverable (UCR) errors : > > Is UCR a well known x86 acronym? It's best to just spell this out each time, > there is enough jargon in this area already. Quite agreed, will replace the commit log with "uncorrected recoverable error". > >> >> - Action Required (AR): The error is detected and the processor already >> consumes the memory. OS requires to take action (for example, offline >> failure page/kill failure thread) to recover this uncorrectable error. >> >> - Action Optional (AO): The error is detected out of processor execution >> context. Some data in the memory are corrupted. But the data have not >> been consumed. OS is optional to take action to recover this >> uncorrectable error. > > As elsewhere, please don't think of errors as 'action required', this is how > things get reported to user-space. Action-required for one thread may be > action-optional for another that has the same page mapped - its really not a > property of the error. > It would be better to describe this as synchronous and asynchronous, or in-band > and out-of-band. Thank you for explanation. I will change to "synchronous and asynchronous". > > >> The essential difference between AR and AO errors is that AR is a >> synchronous event, while AO is an asynchronous event. The hardware will >> signal a synchronous exception (Machine Check Exception on X86 and >> Synchronous External Abort on Arm64) when an error is detected and the >> memory access has been architecturally executed. > >> When APEI firmware first is enabled, a platform may describe one error >> source for the handling of synchronous errors (e.g. MCE or SEA notification >> ), or for handling asynchronous errors (e.g. SCI or External Interrupt >> notification). In other words, we can distinguish synchronous errors by >> APEI notification. For AR errors, kernel will kill current process >> accessing the poisoned page by sending SIGBUS with BUS_MCEERR_AR. In >> addition, for AO errors, kernel will notify the process who owns the >> poisoned page by sending SIGBUS with BUS_MCEERR_AO in early kill mode. >> However, the GHES driver always sets mf_flags to 0 so that all UCR errors >> are handled as AO errors in memory failure. > > To make this easier to read: > UCR and AR -> synchronous > AO -> asynchronous > Will do that. > >> To this end, set memory failure flags as MF_ACTION_REQUIRED on synchronous >> events. > >> Fixes: ba61ca4aab47 ("ACPI, APEI, GHES: Add hardware memory error recovery support")' > > Erm, this predates arm64 support, and what you have here doesn't change the behaviour on x86. > > You can blame 7f17b4a121d0d50 ("ACPI: APEI: Kick the memory_failure() queue for > synchronous errors"), which should have covered this. Do you mean just drop the "Fixes" tags? > >> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c >> index ef59d6ea16da..88178aa6222d 100644 >> --- a/drivers/acpi/apei/ghes.c >> +++ b/drivers/acpi/apei/ghes.c >> @@ -101,6 +101,20 @@ static inline bool is_hest_type_generic_v2(struct ghes *ghes) >> return ghes->generic->header.type == ACPI_HEST_TYPE_GENERIC_ERROR_V2; >> } >> >> +/* >> + * A platform may describe one error source for the handling of synchronous >> + * errors (e.g. MCE or SEA), or for handling asynchronous errors (e.g. SCI >> + * or External Interrupt). On x86, the HEST notifications are always >> + * asynchronous, so only SEA on ARM is delivered as a synchronous >> + * notification. >> + */ >> +static inline bool is_hest_sync_notify(struct ghes *ghes) >> +{ >> + u8 notify_type = ghes->generic->notify.type; >> + >> + return notify_type == ACPI_HEST_NOTIFY_SEA; >> +} > > and as you had in earlier versions, sometimes SDEI. > SDEI can report by synchronous and asynchronous errors, I wouldn't too surprised if the > hardware NMI can be used for the same. It would be good to chase up having a hint of this > in the CPER records and pass that in here as a hint.> > Unfortunately, its not safe to assume either way for SDEI. For SDEI notification, only x0-x17 has preserved by firmware. As SDEI TRM[1] describes "the dispatcher can simulate an exception-like entry into the client, **with the client providing an additional asynchronous entry point similar to an interrupt entry point**". The client (kernel) lacks complete synchronous context, e.g. system register (ELR, ESR, etc). So I think SDEI notification should not be used for asynchronous error, can you help to confirm this? For NMI notification, as far as I know, AArch64 (aka arm64 in the Linux tree) does not provide architected NMIs. > > Reviewed-by: James Morse > Thank you for valuable comments. Best Regards, Shuai [1] https://developer.arm.com/documentation/den0054/latest/