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bh=+tAyefb9X6kRjApZV5oPZWTBz3sh185ettyS9iiaj4k=; b=SAIxxY67l9mMRH/Faczezr5ve+81pDcrAnAaC99+VoNi5JQkP4ip9seIgXGSxq9qu9rcDLzHFx4l943ESRL+xT5/jeaRiLQ8SbD76cSI5yTuAjv31cZNYzTUQZUEk5VQM/eNaCTi4tMNEmNX7By55sRn2vPIwkqaA01RCptMer4= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R151e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046060;MF=xueshuai@linux.alibaba.com;NM=1;PH=DS;RN=32;SR=0;TI=SMTPD_---0W2KiIQW_1710223549; Received: from 30.240.112.150(mailfrom:xueshuai@linux.alibaba.com fp:SMTPD_---0W2KiIQW_1710223549) by smtp.aliyun-inc.com; Tue, 12 Mar 2024 14:05:51 +0800 Message-ID: <2a6642a1-d20d-4588-9e5c-a4693f96fe38@linux.alibaba.com> Date: Tue, 12 Mar 2024 14:05:48 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Shuai Xue Subject: Re: [PATCH v11 3/3] ACPI: APEI: handle synchronous exceptions in task work to send correct SIGBUS si_code To: Borislav Petkov Cc: rafael@kernel.org, wangkefeng.wang@huawei.com, tanxiaofei@huawei.com, mawupeng1@huawei.com, tony.luck@intel.com, linmiaohe@huawei.com, naoya.horiguchi@nec.com, james.morse@arm.com, gregkh@linuxfoundation.org, will@kernel.org, jarkko@kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, linux-edac@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, 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> <20240204080144.7977-4-xueshuai@linux.alibaba.com> <20240308101836.GDZerl_IXIkWt8VuZN@fat_crate.local> Content-Language: en-US In-Reply-To: <20240308101836.GDZerl_IXIkWt8VuZN@fat_crate.local> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2024/3/8 18:18, Borislav Petkov wrote: > On Sun, Feb 04, 2024 at 04:01:44PM +0800, Shuai Xue wrote: >> Hardware errors could be signaled by asynchronous interrupt, e.g. when an >> error is detected by a background scrubber, or signaled by synchronous >> exception, e.g. when a CPU tries to access a poisoned cache line. Since >> commit a70297d22132 ("ACPI: APEI: set memory failure flags as >> MF_ACTION_REQUIRED on synchronous events")', the flag MF_ACTION_REQUIRED >> could be used to determine whether a synchronous exception occurs on ARM64 >> platform. When a synchronous exception is detected, the kernel should >> terminate the current process which accessing the poisoned page. This is > > "which has accessed poison data" Thank you. Will fix the grammer. > >> done by sending a SIGBUS signal with an error code BUS_MCEERR_AR, >> indicating an action-required machine check error on read. >> >> However, the memory failure recovery is incorrectly sending a SIGBUS >> with wrong error code BUS_MCEERR_AO for synchronous errors in early kill >> mode, even MF_ACTION_REQUIRED is set. The main problem is that > > "even if" Thank you. Will fix the grammer. > >> synchronous errors are queued as a memory_failure() work, and are >> executed within a kernel thread context, not the user-space process that >> encountered the corrupted memory on ARM64 platform. As a result, when >> kill_proc() is called to terminate the process, it sends the incorrect >> SIGBUS error code because the context in which it operates is not the >> one where the error was triggered. >> >> To this end, queue memory_failure() as a task_work so that it runs in >> the context of the process that is actually consuming the poisoned data, >> and it will send SIBBUS with si_code BUS_MCEERR_AR. > > SIGBUS Sorry, will fix the typo. > >> >> Signed-off-by: Shuai Xue >> Tested-by: Ma Wupeng >> Reviewed-by: Kefeng Wang >> Reviewed-by: Xiaofei Tan >> Reviewed-by: Baolin Wang >> --- >> drivers/acpi/apei/ghes.c | 77 +++++++++++++++++++++++----------------- >> include/acpi/ghes.h | 3 -- >> mm/memory-failure.c | 13 ------- >> 3 files changed, 44 insertions(+), 49 deletions(-) >> >> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c >> index 0892550732d4..e5086d795bee 100644 >> --- a/drivers/acpi/apei/ghes.c >> +++ b/drivers/acpi/apei/ghes.c >> @@ -465,28 +465,41 @@ 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 > > What's so special about it being a "sync_"? > > task_work is just fine and something else could use it too. You are right, the `sync_task_work` is only use for synchronous RAS event right, but it could be also use for other purpose in the future. The purpose can be specified through flags. I will remove the `sync_` prefix. > >> + * >> + * @twork: callback_head for task work >> + * @pfn: page frame number of corrupted page >> + * @flags: fine tune action taken > > s/fine tune action taken/work control flags/ > Will fix it. >> + * >> + * Structure to pass task work to be handled before >> + * ret_to_user via task_work_add(). > > What is "ret_to_user"? > > If this is an ARM thing, then make sure you explain stuff properly and > detailed. This driver is used by multiple architectures. It is not ARM specific thing. I mean it is used by task_work before returning to user-space. + * Structure to pass task work to be handled before + * returning to user-space 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); > > Ugly linebreak - no need for it. Will fix it. > >> - 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); >> + gen_pool_free(ghes_estatus_pool, (unsigned long)twcb, sizeof(*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 || ret == -EHWPOISON || ret == -EOPNOTSUPP) >> + return; >> + >> + pr_err("Sending SIGBUS to current task due to memory error not recovered"); >> + force_sig(SIGBUS); >> } >> >> static bool 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; >> @@ -499,6 +512,18 @@ static bool ghes_do_memory_failure(u64 physical_addr, int flags) >> return false; >> } >> >> + if (flags == MF_ACTION_REQUIRED && current->mm) { >> + twcb = (void *)gen_pool_alloc(ghes_estatus_pool, sizeof(*twcb)); >> + if (!twcb) >> + return false; >> + >> + twcb->pfn = pfn; >> + twcb->flags = flags; >> + init_task_work(&twcb->twork, memory_failure_cb); >> + task_work_add(current, &twcb->twork, TWA_RESUME); >> + return true; >> + } >> + >> memory_failure_queue(pfn, flags); >> return true; >> } >> @@ -746,7 +771,7 @@ int cxl_cper_unregister_callback(cxl_cper_callback callback) >> } >> EXPORT_SYMBOL_NS_GPL(cxl_cper_unregister_callback, CXL); >> >> -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; >> @@ -814,8 +839,6 @@ static bool ghes_do_proc(struct ghes *ghes, >> pr_err("Sending SIGBUS to current task due to memory error not recovered"); >> force_sig(SIGBUS); >> } >> - >> - return queued; >> } >> >> static void __ghes_print_estatus(const char *pfx, >> @@ -1117,9 +1140,7 @@ 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); >> /* >> @@ -1134,25 +1155,16 @@ 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); > > I have no clue why this is being removed. Before this patch, a memory_failure() work is queued into workqueue for both the asynchronous interrupt and synchronous exception. So memory_failure() will be executed asynchronously. For NMIlike notifications, commit 7f17b4a121d0 ("ACPI: APEI: Kick the memory_failure() queue for synchronous errors") keeps track of whether memory_failure() work was queued, and makes task_work pending to flush out the queue. It ensures any queued work has been done before we return to the context that triggered the notification. In this patch: - a memory_failure() work is queued into workqueue for asynchronous interrupt - a memory_failure() task_work is queued by task_work_add for synchronous exception The memory_failure() task_work will be handled before returning to user space, so we does not need to queue a flushing task_work any anymore. > > Why doesn't a synchronous exception on ARM call into ghes_proc_in_irq()? /* * SEA can interrupt SError, mask it and describe this as an NMI so * that APEI defers the handling. */ local_daif_restore(DAIF_ERRCTX); nmi_enter(); => ghes_notify_sea => ghes_in_nmi_spool_from_list => ghes_in_nmi_queue_one_entry // also called in __ghes_sdei_callback => irq_work_queue(&ghes_proc_irq_work); nmi_exit(); > > That SDEI thing certainly does. > > Well looka here: > > 7f17b4a121d0 ("ACPI: APEI: Kick the memory_failure() queue for synchronous errors") > > that thing does exactly what you're trying to "fix". So why doesn't that > work for you? > Commit a70297d22132 (ACPI: APEI: set memory failure flags as MF_ACTION_REQUIRED on synchronous events) set MF_ACTION_REQUIRED for synchronous events. /* * Send all the processes who have the page mapped a signal. * ``action optional'' if they are not immediately affected by the error * ``action required'' if error happened in current execution context */ static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags) { ... if ((flags & MF_ACTION_REQUIRED) && (t == current)) ret = force_sig_mceerr(BUS_MCEERR_AR, (void __user *)tk->addr, addr_lsb); else ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr, addr_lsb, t); ... } Because the memory_failure() running in a kthread context, the false branch in kill_proc() will send SIGBUS with BUS_MCEERR_AO. But we except it as a BUS_MCEERR_AR. Thank you for valuable comments :) Best Regards, Shuai