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 C10B3C77B6C for ; Fri, 7 Apr 2023 02:21:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240563AbjDGCVl (ORCPT ); Thu, 6 Apr 2023 22:21:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57712 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240459AbjDGCVi (ORCPT ); Thu, 6 Apr 2023 22:21:38 -0400 Received: from out30-101.freemail.mail.aliyun.com (out30-101.freemail.mail.aliyun.com [115.124.30.101]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F030CA9; Thu, 6 Apr 2023 19:21:35 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R121e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046051;MF=xueshuai@linux.alibaba.com;NM=1;PH=DS;RN=22;SR=0;TI=SMTPD_---0VfUsHeY_1680834088; Received: from 30.240.113.3(mailfrom:xueshuai@linux.alibaba.com fp:SMTPD_---0VfUsHeY_1680834088) by smtp.aliyun-inc.com; Fri, 07 Apr 2023 10:21:30 +0800 Message-ID: <80aa34b5-0957-411b-e990-afc7adc6ebd8@linux.alibaba.com> Date: Fri, 7 Apr 2023 10:21:25 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH v3 2/2] ACPI: APEI: handle synchronous exceptions in task work Content-Language: en-US To: Xiaofei Tan , tony.luck@intel.com, naoya.horiguchi@nec.com Cc: linux-acpi@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, justin.he@arm.com, akpm@linux-foundation.org, ardb@kernel.org, ashish.kalra@amd.com, baolin.wang@linux.alibaba.com, bp@alien8.de, cuibixuan@linux.alibaba.com, dave.hansen@linux.intel.com, james.morse@arm.com, jarkko@kernel.org, lenb@kernel.org, linmiaohe@huawei.com, lvying6@huawei.com, rafael@kernel.org, xiexiuqi@huawei.com, zhuo.song@linux.alibaba.com References: <20221027042445.60108-1-xueshuai@linux.alibaba.com> <20230317072443.3189-3-xueshuai@linux.alibaba.com> From: Shuai Xue In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/4/6 PM8:39, Xiaofei Tan wrote: > Hi Shuai, > > Thanks for your this effort, and it's great. > Some comments below. > > 在 2023/3/17 15:24, Shuai Xue 写道: >> Hardware errors could be signaled by synchronous interrupt, e.g.  when an >> error is detected by a background scrubber, or signaled by synchronous >> exception, e.g. when an uncorrected error is consumed. Both synchronous and >> asynchronous error are queued and handled by a dedicated kthread in >> workqueue. >> >> commit 7f17b4a121d0 ("ACPI: APEI: Kick the memory_failure() queue for >> synchronous errors") keep track of whether memory_failure() work was >> queued, and make task_work pending to flush out the workqueue so that the >> work for synchronous error is processed before returning to user-space. >> The trick ensures that the corrupted page is unmapped and poisoned. And >> after returning to user-space, the task starts at current instruction which >> triggering a page fault in which kernel will send SIGBUS to current process >> due to VM_FAULT_HWPOISON. >> >> However, the memory failure recovery for hwpoison-aware mechanisms does not >> work as expected. For example, hwpoison-aware user-space processes like >> QEMU register their customized SIGBUS handler and enable early kill mode by >> seting PF_MCE_EARLY at initialization. Then the kernel will directy notify >> the process by sending a SIGBUS signal in memory failure with wrong >> si_code: the actual user-space process accessing the corrupt memory >> location, but its memory failure work is handled in a kthread context, so >> it will send SIGBUS with BUS_MCEERR_AO si_code to the actual user-space >> process instead of BUS_MCEERR_AR in kill_proc(). >> >> To this end, separate synchronous and asynchronous error handling into >> different paths like X86 platform does: >> >> - task work for synchronous errors. >> - and workqueue for asynchronous errors. >> >> Then for synchronous errors, the current context in memory failure is >> exactly belongs to the task consuming poison data and it will send SIBBUS >> with proper si_code. >> >> Fixes: 7f17b4a121d0 ("ACPI: APEI: Kick the memory_failure() queue for synchronous errors") >> Signed-off-by: Shuai Xue >> --- >>   drivers/acpi/apei/ghes.c | 114 ++++++++++++++++++++++----------------- >>   include/acpi/ghes.h      |   3 -- >>   mm/memory-failure.c      |  13 ----- >>   3 files changed, 64 insertions(+), 66 deletions(-) >> >> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c >> index cccd96596efe..1901ee3498c4 100644 >> --- a/drivers/acpi/apei/ghes.c >> +++ b/drivers/acpi/apei/ghes.c >> @@ -452,45 +452,79 @@ static void ghes_clear_estatus(struct ghes *ghes, >>   } >>     /* >> - * Called as task_work before returning to user-space. >> - * Ensure any queued work has been done before we return to the context that >> - * triggered the notification. >> + * struct sync_task_work - for synchronous RAS event >> + * >> + * @twork:                callback_head for task work >> + * @pfn:                  page frame number of corrupted page >> + * @flags:                fine tune action taken >> + * >> + * Structure to pass task work to be handled before >> + * ret_to_user via task_work_add(). >>    */ >> -static void ghes_kick_task_work(struct callback_head *head) >> +struct sync_task_work { >> +    struct callback_head twork; >> +    u64 pfn; >> +    int flags; >> +}; >> + >> +static void memory_failure_cb(struct callback_head *twork) >>   { >> -    struct acpi_hest_generic_status *estatus; >> -    struct ghes_estatus_node *estatus_node; >> -    u32 node_len; >> +    int ret; >> +    struct sync_task_work *twcb = >> +        container_of(twork, struct sync_task_work, twork); >>   -    estatus_node = container_of(head, struct ghes_estatus_node, task_work); >> -    if (IS_ENABLED(CONFIG_ACPI_APEI_MEMORY_FAILURE)) >> -        memory_failure_queue_kick(estatus_node->task_work_cpu); >> +    ret = memory_failure(twcb->pfn, twcb->flags); >> +    kfree(twcb); >>   -    estatus = GHES_ESTATUS_FROM_NODE(estatus_node); >> -    node_len = GHES_ESTATUS_NODE_LEN(cper_estatus_len(estatus)); >> -    gen_pool_free(ghes_estatus_pool, (unsigned long)estatus_node, node_len); >> +    if (!ret) >> +        return; >> + >> +    /* >> +     * -EHWPOISON from memory_failure() means that it already sent SIGBUS >> +     * to the current process with the proper error info, >> +     * -EOPNOTSUPP means hwpoison_filter() filtered the error event, >> +     * >> +     * In both cases, no further processing is required. >> +     */ >> +    if (ret == -EHWPOISON || ret == -EOPNOTSUPP) >> +        return; >> + >> +    pr_err("Memory error not recovered"); >> +    force_sig(SIGBUS); >>   } >>   -static bool ghes_do_memory_failure(u64 physical_addr, int flags) >> +static void ghes_do_memory_failure(u64 physical_addr, int flags) >>   { >>       unsigned long pfn; >> +    struct sync_task_work *twcb; >>         if (!IS_ENABLED(CONFIG_ACPI_APEI_MEMORY_FAILURE)) >> -        return false; >> +        return; >>         pfn = PHYS_PFN(physical_addr); >>       if (!pfn_valid(pfn) && !arch_is_platform_page(physical_addr)) { >>           pr_warn_ratelimited(FW_WARN GHES_PFX >>           "Invalid address in generic error data: %#llx\n", >>           physical_addr); >> -        return false; >> +        return; > > For synchronous errors, we need send SIGBUS to the current task if not recovered, > as the behavior of this patch  in the function memory_failure_cb(). > Such abnormal branches should also be taken as not recovered. You are right. Thank you for pointing this out. I overlooked the abnormal branches. To sum up, there are three cases: - valid synchronous errors: queue a task_work to synchronously send SIGBUS before ret_to_user. - valid asynchronous errors: queue a work into workqueue to asynchronously handle memory failure. - abnormal branches such as invalid PA, unexpected severity, no memory failure config support, invalid GUID section, OOM, etc. As you commented, abnormal branches case should also be send SIGBUS, I will handle it in ghes_proc_in_irq() if no work (task work or workqueue work) is queued. Best Regards, Shuai > > >> +    } >> + >> +    if (flags == MF_ACTION_REQUIRED && current->mm) { >> +        twcb = kmalloc(sizeof(*twcb), GFP_ATOMIC); >> +        if (!twcb) >> +            return; > > It's the same here. > > >> + >> +        twcb->pfn = pfn; >> +        twcb->flags = flags; >> +        init_task_work(&twcb->twork, memory_failure_cb); >> +        task_work_add(current, &twcb->twork, TWA_RESUME); >> +        return; >>       } >>         memory_failure_queue(pfn, flags); >> -    return true; >>   } >>   -static bool ghes_handle_memory_failure(struct acpi_hest_generic_data *gdata, >> +static void ghes_handle_memory_failure(struct acpi_hest_generic_data *gdata, >>                          int sev, bool sync) >>   { >>       int flags = -1; >> @@ -498,7 +532,7 @@ static bool ghes_handle_memory_failure(struct acpi_hest_generic_data *gdata, >>       struct cper_sec_mem_err *mem_err = acpi_hest_get_payload(gdata); >>         if (!(mem_err->validation_bits & CPER_MEM_VALID_PA)) >> -        return false; >> +        return; > > and here. > > >>         /* iff following two events can be handled properly by now */ >>       if (sec_sev == GHES_SEV_CORRECTED && >> @@ -508,16 +542,15 @@ static bool ghes_handle_memory_failure(struct acpi_hest_generic_data *gdata, >>           flags = sync ? MF_ACTION_REQUIRED : 0; >>         if (flags != -1) >> -        return ghes_do_memory_failure(mem_err->physical_addr, flags); >> +        ghes_do_memory_failure(mem_err->physical_addr, flags); >>   -    return false; >> +    return; >>   } >>   -static bool ghes_handle_arm_hw_error(struct acpi_hest_generic_data *gdata, >> +static void ghes_handle_arm_hw_error(struct acpi_hest_generic_data *gdata, >>                          int sev, bool sync) >>   { >>       struct cper_sec_proc_arm *err = acpi_hest_get_payload(gdata); >> -    bool queued = false; >>       int sec_sev, i; >>       char *p; >>       int flags = sync ? MF_ACTION_REQUIRED : 0; >> @@ -526,7 +559,7 @@ static bool ghes_handle_arm_hw_error(struct acpi_hest_generic_data *gdata, >>         sec_sev = ghes_severity(gdata->error_severity); >>       if (sev != GHES_SEV_RECOVERABLE || sec_sev != GHES_SEV_RECOVERABLE) >> -        return false; >> +        return; > > and here. > > >>         p = (char *)(err + 1); >>       for (i = 0; i < err->err_info_num; i++) { >> @@ -542,7 +575,7 @@ static bool ghes_handle_arm_hw_error(struct acpi_hest_generic_data *gdata, >>            * and don't filter out 'corrected' error here. >>            */ >>           if (is_cache && has_pa) { >> -            queued = ghes_do_memory_failure(err_info->physical_fault_addr, flags); >> +            ghes_do_memory_failure(err_info->physical_fault_addr, flags); >>               p += err_info->length; >>               continue; >>           } >> @@ -555,8 +588,6 @@ static bool ghes_handle_arm_hw_error(struct acpi_hest_generic_data *gdata, >>                       error_type); >>           p += err_info->length; >>       } > > and here, for the case that memory failure is not done, as PA is invalid. > > >> - >> -    return queued; >>   } >>     /* >> @@ -654,7 +685,7 @@ static void ghes_defer_non_standard_event(struct acpi_hest_generic_data *gdata, >>       schedule_work(&entry->work); >>   } >>   -static bool ghes_do_proc(struct ghes *ghes, >> +static void ghes_do_proc(struct ghes *ghes, >>                const struct acpi_hest_generic_status *estatus) >>   { >>       int sev, sec_sev; >> @@ -662,7 +693,6 @@ static bool ghes_do_proc(struct ghes *ghes, >>       guid_t *sec_type; >>       const guid_t *fru_id = &guid_null; >>       char *fru_text = ""; >> -    bool queued = false; >>       bool sync = is_hest_sync_notify(ghes); >>         sev = ghes_severity(estatus->error_severity); >> @@ -681,13 +711,13 @@ static bool ghes_do_proc(struct ghes *ghes, >>               atomic_notifier_call_chain(&ghes_report_chain, sev, mem_err); >>                 arch_apei_report_mem_error(sev, mem_err); >> -            queued = ghes_handle_memory_failure(gdata, sev, sync); >> +            ghes_handle_memory_failure(gdata, sev, sync); >>           } >>           else if (guid_equal(sec_type, &CPER_SEC_PCIE)) { >>               ghes_handle_aer(gdata); >>           } >>           else if (guid_equal(sec_type, &CPER_SEC_PROC_ARM)) { >> -            queued = ghes_handle_arm_hw_error(gdata, sev, sync); >> +            ghes_handle_arm_hw_error(gdata, sev, sync); >>           } else { >>               void *err = acpi_hest_get_payload(gdata); >>   @@ -697,8 +727,6 @@ static bool ghes_do_proc(struct ghes *ghes, >>                              gdata->error_data_length); >>           } >>       } >> - >> -    return queued; >>   } >>     static void __ghes_print_estatus(const char *pfx, >> @@ -1000,9 +1028,7 @@ static void ghes_proc_in_irq(struct irq_work *irq_work) >>       struct ghes_estatus_node *estatus_node; >>       struct acpi_hest_generic *generic; >>       struct acpi_hest_generic_status *estatus; >> -    bool task_work_pending; >>       u32 len, node_len; >> -    int ret; >>         llnode = llist_del_all(&ghes_estatus_llist); >>       /* >> @@ -1017,25 +1043,14 @@ static void ghes_proc_in_irq(struct irq_work *irq_work) >>           estatus = GHES_ESTATUS_FROM_NODE(estatus_node); >>           len = cper_estatus_len(estatus); >>           node_len = GHES_ESTATUS_NODE_LEN(len); >> -        task_work_pending = ghes_do_proc(estatus_node->ghes, estatus); >> +        ghes_do_proc(estatus_node->ghes, estatus); >>           if (!ghes_estatus_cached(estatus)) { >>               generic = estatus_node->generic; >>               if (ghes_print_estatus(NULL, generic, estatus)) >>                   ghes_estatus_cache_add(generic, estatus); >>           } >> - >> -        if (task_work_pending && current->mm) { >> -            estatus_node->task_work.func = ghes_kick_task_work; >> -            estatus_node->task_work_cpu = smp_processor_id(); >> -            ret = task_work_add(current, &estatus_node->task_work, >> -                        TWA_RESUME); >> -            if (ret) >> -                estatus_node->task_work.func = NULL; >> -        } >> - >> -        if (!estatus_node->task_work.func) >> -            gen_pool_free(ghes_estatus_pool, >> -                      (unsigned long)estatus_node, node_len); >> +        gen_pool_free(ghes_estatus_pool, (unsigned long)estatus_node, >> +                  node_len); >>             llnode = next; >>       } >> @@ -1096,7 +1111,6 @@ static int ghes_in_nmi_queue_one_entry(struct ghes *ghes, >>         estatus_node->ghes = ghes; >>       estatus_node->generic = ghes->generic; >> -    estatus_node->task_work.func = NULL; >>       estatus = GHES_ESTATUS_FROM_NODE(estatus_node); >>         if (__ghes_read_estatus(estatus, buf_paddr, fixmap_idx, len)) { >> diff --git a/include/acpi/ghes.h b/include/acpi/ghes.h >> index 3c8bba9f1114..e5e0c308d27f 100644 >> --- a/include/acpi/ghes.h >> +++ b/include/acpi/ghes.h >> @@ -35,9 +35,6 @@ struct ghes_estatus_node { >>       struct llist_node llnode; >>       struct acpi_hest_generic *generic; >>       struct ghes *ghes; >> - >> -    int task_work_cpu; >> -    struct callback_head task_work; >>   }; >>     struct ghes_estatus_cache { >> diff --git a/mm/memory-failure.c b/mm/memory-failure.c >> index fae9baf3be16..6ea8c325acb3 100644 >> --- a/mm/memory-failure.c >> +++ b/mm/memory-failure.c >> @@ -2355,19 +2355,6 @@ static void memory_failure_work_func(struct work_struct *work) >>       } >>   } >>   -/* >> - * Process memory_failure work queued on the specified CPU. >> - * Used to avoid return-to-userspace racing with the memory_failure workqueue. >> - */ >> -void memory_failure_queue_kick(int cpu) >> -{ >> -    struct memory_failure_cpu *mf_cpu; >> - >> -    mf_cpu = &per_cpu(memory_failure_cpu, cpu); >> -    cancel_work_sync(&mf_cpu->work); >> -    memory_failure_work_func(&mf_cpu->work); >> -} >> - >>   static int __init memory_failure_init(void) >>   { >>       struct memory_failure_cpu *mf_cpu;