| Message ID | 20241202030527.20586-4-xueshuai@linux.alibaba.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | ACPI: APEI: handle synchronous errors in task work | expand |
On 12/1/2024 7:05 PM, Shuai Xue wrote: > The memory uncorrected error could be signaled by asynchronous interrupt > (specifically, SPI in arm64 platform), e.g. when an error is detected by > a background scrubber, or signaled by synchronous exception > (specifically, data abort exception in arm64 platform), e.g. when a CPU > tries to access a poisoned cache line. Currently, both synchronous and > asynchronous error use memory_failure_queue() to schedule > memory_failure() to exectute in a kworker context. > > As a result, when a user-space process is accessing a poisoned data, a > data abort is taken and the memory_failure() is executed in the kworker > context, memory_failure(): > > - will send wrong si_code by SIGBUS signal in early_kill mode, and > - can not kill the user-space in some cases resulting a synchronous > error infinite loop > > Issue 1: send wrong si_code in early_kill mode > > 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 is > expected to terminate the current process which has accessed poisoned > page. This is done by sending a SIGBUS signal with an error code > BUS_MCEERR_AR, indicating an action-required machine check error on > read. > > However, when kill_proc() is called to terminate the processes who have > the poisoned page mapped, it sends the incorrect SIGBUS error code > BUS_MCEERR_AO because the context in which it operates is not the one > where the error was triggered. > > To reproduce this problem: > > #sysctl -w vm.memory_failure_early_kill=1 > vm.memory_failure_early_kill = 1 > > # STEP2: inject an UCE error and consume it to trigger a synchronous error > #einj_mem_uc single > 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 > injecting ... > triggering ... > signal 7 code 5 addr 0xffffb0d75000 > page not present > Test passed > > The si_code (code 5) from einj_mem_uc indicates that it is BUS_MCEERR_AO > error and it is not the fact. > > After this patch: > > # STEP1: enable early kill mode > #sysctl -w vm.memory_failure_early_kill=1 > vm.memory_failure_early_kill = 1 > # STEP2: inject an UCE error and consume it to trigger a synchronous error > #einj_mem_uc single > 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 > injecting ... > triggering ... > signal 7 code 4 addr 0xffffb0d75000 > page not present > Test passed > > The si_code (code 4) from einj_mem_uc indicates that it is a BUS_MCEERR_AR > error as we expected. > > Issue 2: a synchronous error infinite loop > > If a user-space process, e.g. devmem, accesses a poisoned page for which > the HWPoison flag is set, kill_accessing_process() is called to send > SIGBUS to current processs with error info. Because the memory_failure() > is executed in the kworker context, it will just do nothing but return > EFAULT. So, devmem will access the posioned page and trigger an > exception again, resulting in a synchronous error infinite loop. Such > exception loop may cause platform firmware to exceed some threshold and > reboot when Linux could have recovered from this error. > > To reproduce this problem: > > # STEP 1: inject an UCE error, and kernel will set HWPosion flag for related page > #einj_mem_uc single > 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 > injecting ... > triggering ... > signal 7 code 4 addr 0xffffb0d75000 > page not present > Test passed > > # STEP 2: access the same page and it will trigger a synchronous error infinite loop > devmem 0x4092d55b400 > > To fix above two issues, queue memory_failure() as a task_work so that > it runs in the context of the process that is actually consuming the > poisoned data. > > Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com> > Tested-by: Ma Wupeng <mawupeng1@huawei.com> > Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com> > Reviewed-by: Xiaofei Tan <tanxiaofei@huawei.com> > Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> > Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> > --- > drivers/acpi/apei/ghes.c | 77 +++++++++++++++++++++++----------------- > include/acpi/ghes.h | 3 -- > include/linux/mm.h | 1 - > mm/memory-failure.c | 13 ------- > 4 files changed, 44 insertions(+), 50 deletions(-) > > diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c > index 106486bdfefc..70f2ee3ad1a8 100644 > --- a/drivers/acpi/apei/ghes.c > +++ b/drivers/acpi/apei/ghes.c > @@ -467,28 +467,41 @@ 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 ghes_task_work - for synchronous RAS event > + * > + * @twork: callback_head for task work > + * @pfn: page frame number of corrupted page > + * @flags: work control flags > + * > + * 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 ghes_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; > + struct ghes_task_work *twcb = container_of(twork, struct ghes_task_work, twork); > + int ret; > > - 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("%#llx: Sending SIGBUS to %s:%d due to hardware memory corruption\n", > + twcb->pfn, current->comm, task_pid_nr(current)); > + force_sig(SIGBUS); > } > > static bool ghes_do_memory_failure(u64 physical_addr, int flags) > { > unsigned long pfn; > + struct ghes_task_work *twcb; > > if (!IS_ENABLED(CONFIG_ACPI_APEI_MEMORY_FAILURE)) > return false; > @@ -501,6 +514,18 @@ 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; > } > @@ -745,7 +770,7 @@ int cxl_cper_kfifo_get(struct cxl_cper_work_data *wd) > } > EXPORT_SYMBOL_NS_GPL(cxl_cper_kfifo_get, 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; > @@ -811,8 +836,6 @@ static bool ghes_do_proc(struct ghes *ghes, > current->comm, task_pid_nr(current)); > force_sig(SIGBUS); > } > - > - return queued; > } > > static void __ghes_print_estatus(const char *pfx, > @@ -1114,9 +1137,7 @@ 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); > /* > @@ -1131,25 +1152,16 @@ 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); > + gen_pool_free(ghes_estatus_pool, (unsigned long)estatus_node, > + node_len); > > llnode = next; > } > @@ -1210,7 +1222,6 @@ 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 be1dd4c1a917..ebd21b05fe6e 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/include/linux/mm.h b/include/linux/mm.h > index c39c4945946c..aa4246c7c23e 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -3936,7 +3936,6 @@ enum mf_flags { > int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index, > unsigned long count, int mf_flags); > extern int memory_failure(unsigned long pfn, int flags); > -extern void memory_failure_queue_kick(int cpu); > extern int unpoison_memory(unsigned long pfn); > extern atomic_long_t num_poisoned_pages __read_mostly; > extern int soft_offline_page(unsigned long pfn, int flags); > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index 14c316d7d38d..e0adb665d07b 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -2499,19 +2499,6 @@ 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; Looks good. Reviewed-by: Jane Chu <jane.chu@oracle.com> -jane
在 2024/12/17 07:53, jane.chu@oracle.com 写道: > > On 12/1/2024 7:05 PM, Shuai Xue wrote: >> The memory uncorrected error could be signaled by asynchronous interrupt >> (specifically, SPI in arm64 platform), e.g. when an error is detected by >> a background scrubber, or signaled by synchronous exception >> (specifically, data abort exception in arm64 platform), e.g. when a CPU >> tries to access a poisoned cache line. Currently, both synchronous and >> asynchronous error use memory_failure_queue() to schedule >> memory_failure() to exectute in a kworker context. >> >> As a result, when a user-space process is accessing a poisoned data, a >> data abort is taken and the memory_failure() is executed in the kworker >> context, memory_failure(): >> >> - will send wrong si_code by SIGBUS signal in early_kill mode, and >> - can not kill the user-space in some cases resulting a synchronous >> error infinite loop >> >> Issue 1: send wrong si_code in early_kill mode >> >> 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 is >> expected to terminate the current process which has accessed poisoned >> page. This is done by sending a SIGBUS signal with an error code >> BUS_MCEERR_AR, indicating an action-required machine check error on >> read. >> >> However, when kill_proc() is called to terminate the processes who have >> the poisoned page mapped, it sends the incorrect SIGBUS error code >> BUS_MCEERR_AO because the context in which it operates is not the one >> where the error was triggered. >> >> To reproduce this problem: >> >> #sysctl -w vm.memory_failure_early_kill=1 >> vm.memory_failure_early_kill = 1 >> >> # STEP2: inject an UCE error and consume it to trigger a synchronous error >> #einj_mem_uc single >> 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 >> injecting ... >> triggering ... >> signal 7 code 5 addr 0xffffb0d75000 >> page not present >> Test passed >> >> The si_code (code 5) from einj_mem_uc indicates that it is BUS_MCEERR_AO >> error and it is not the fact. >> >> After this patch: >> >> # STEP1: enable early kill mode >> #sysctl -w vm.memory_failure_early_kill=1 >> vm.memory_failure_early_kill = 1 >> # STEP2: inject an UCE error and consume it to trigger a synchronous error >> #einj_mem_uc single >> 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 >> injecting ... >> triggering ... >> signal 7 code 4 addr 0xffffb0d75000 >> page not present >> Test passed >> >> The si_code (code 4) from einj_mem_uc indicates that it is a BUS_MCEERR_AR >> error as we expected. >> >> Issue 2: a synchronous error infinite loop >> >> If a user-space process, e.g. devmem, accesses a poisoned page for which >> the HWPoison flag is set, kill_accessing_process() is called to send >> SIGBUS to current processs with error info. Because the memory_failure() >> is executed in the kworker context, it will just do nothing but return >> EFAULT. So, devmem will access the posioned page and trigger an >> exception again, resulting in a synchronous error infinite loop. Such >> exception loop may cause platform firmware to exceed some threshold and >> reboot when Linux could have recovered from this error. >> >> To reproduce this problem: >> >> # STEP 1: inject an UCE error, and kernel will set HWPosion flag for related page >> #einj_mem_uc single >> 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 >> injecting ... >> triggering ... >> signal 7 code 4 addr 0xffffb0d75000 >> page not present >> Test passed >> >> # STEP 2: access the same page and it will trigger a synchronous error infinite loop >> devmem 0x4092d55b400 >> >> To fix above two issues, queue memory_failure() as a task_work so that >> it runs in the context of the process that is actually consuming the >> poisoned data. >> >> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com> >> Tested-by: Ma Wupeng <mawupeng1@huawei.com> >> Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com> >> Reviewed-by: Xiaofei Tan <tanxiaofei@huawei.com> >> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> >> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> >> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> >> --- >> drivers/acpi/apei/ghes.c | 77 +++++++++++++++++++++++----------------- >> include/acpi/ghes.h | 3 -- >> include/linux/mm.h | 1 - >> mm/memory-failure.c | 13 ------- >> 4 files changed, 44 insertions(+), 50 deletions(-) >> >> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c >> index 106486bdfefc..70f2ee3ad1a8 100644 >> --- a/drivers/acpi/apei/ghes.c >> +++ b/drivers/acpi/apei/ghes.c >> @@ -467,28 +467,41 @@ 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 ghes_task_work - for synchronous RAS event >> + * >> + * @twork: callback_head for task work >> + * @pfn: page frame number of corrupted page >> + * @flags: work control flags >> + * >> + * 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 ghes_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; >> + struct ghes_task_work *twcb = container_of(twork, struct ghes_task_work, twork); >> + int ret; >> - 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("%#llx: Sending SIGBUS to %s:%d due to hardware memory corruption\n", >> + twcb->pfn, current->comm, task_pid_nr(current)); >> + force_sig(SIGBUS); >> } >> static bool ghes_do_memory_failure(u64 physical_addr, int flags) >> { >> unsigned long pfn; >> + struct ghes_task_work *twcb; >> if (!IS_ENABLED(CONFIG_ACPI_APEI_MEMORY_FAILURE)) >> return false; >> @@ -501,6 +514,18 @@ 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; >> } >> @@ -745,7 +770,7 @@ int cxl_cper_kfifo_get(struct cxl_cper_work_data *wd) >> } >> EXPORT_SYMBOL_NS_GPL(cxl_cper_kfifo_get, 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; >> @@ -811,8 +836,6 @@ static bool ghes_do_proc(struct ghes *ghes, >> current->comm, task_pid_nr(current)); >> force_sig(SIGBUS); >> } >> - >> - return queued; >> } >> static void __ghes_print_estatus(const char *pfx, >> @@ -1114,9 +1137,7 @@ 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); >> /* >> @@ -1131,25 +1152,16 @@ 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); >> + gen_pool_free(ghes_estatus_pool, (unsigned long)estatus_node, >> + node_len); >> llnode = next; >> } >> @@ -1210,7 +1222,6 @@ 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 be1dd4c1a917..ebd21b05fe6e 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/include/linux/mm.h b/include/linux/mm.h >> index c39c4945946c..aa4246c7c23e 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -3936,7 +3936,6 @@ enum mf_flags { >> int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index, >> unsigned long count, int mf_flags); >> extern int memory_failure(unsigned long pfn, int flags); >> -extern void memory_failure_queue_kick(int cpu); >> extern int unpoison_memory(unsigned long pfn); >> extern atomic_long_t num_poisoned_pages __read_mostly; >> extern int soft_offline_page(unsigned long pfn, int flags); >> diff --git a/mm/memory-failure.c b/mm/memory-failure.c >> index 14c316d7d38d..e0adb665d07b 100644 >> --- a/mm/memory-failure.c >> +++ b/mm/memory-failure.c >> @@ -2499,19 +2499,6 @@ 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; > > Looks good. > > Reviewed-by: Jane Chu <jane.chu@oracle.com> > > -jane > Thanks. Best Regards, Shuai
On Mon, Dec 02, 2024 at 11:05:27AM +0800, Shuai Xue wrote: > The memory uncorrected error could be signaled by asynchronous interrupt > (specifically, SPI in arm64 platform), e.g. when an error is detected by > a background scrubber, or signaled by synchronous exception > (specifically, data abort exception in arm64 platform), e.g. when a CPU > tries to access a poisoned cache line. Currently, both synchronous and > asynchronous error use memory_failure_queue() to schedule > memory_failure() to exectute in a kworker context. > > As a result, when a user-space process is accessing a poisoned data, a > data abort is taken and the memory_failure() is executed in the kworker > context, memory_failure(): > > - will send wrong si_code by SIGBUS signal in early_kill mode, and > - can not kill the user-space in some cases resulting a synchronous > error infinite loop > > Issue 1: send wrong si_code in early_kill mode > > 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 is > expected to terminate the current process which has accessed poisoned > page. This is done by sending a SIGBUS signal with an error code > BUS_MCEERR_AR, indicating an action-required machine check error on > read. > > However, when kill_proc() is called to terminate the processes who have > the poisoned page mapped, it sends the incorrect SIGBUS error code > BUS_MCEERR_AO because the context in which it operates is not the one > where the error was triggered. > > To reproduce this problem: > > #sysctl -w vm.memory_failure_early_kill=1 > vm.memory_failure_early_kill = 1 > > # STEP2: inject an UCE error and consume it to trigger a synchronous error > #einj_mem_uc single > 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 > injecting ... > triggering ... > signal 7 code 5 addr 0xffffb0d75000 > page not present > Test passed > > The si_code (code 5) from einj_mem_uc indicates that it is BUS_MCEERR_AO > error and it is not the fact. > > After this patch: > > # STEP1: enable early kill mode > #sysctl -w vm.memory_failure_early_kill=1 > vm.memory_failure_early_kill = 1 > # STEP2: inject an UCE error and consume it to trigger a synchronous error > #einj_mem_uc single > 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 > injecting ... > triggering ... > signal 7 code 4 addr 0xffffb0d75000 > page not present > Test passed > > The si_code (code 4) from einj_mem_uc indicates that it is a BUS_MCEERR_AR > error as we expected. > > Issue 2: a synchronous error infinite loop > > If a user-space process, e.g. devmem, accesses a poisoned page for which > the HWPoison flag is set, kill_accessing_process() is called to send > SIGBUS to current processs with error info. Because the memory_failure() > is executed in the kworker context, it will just do nothing but return > EFAULT. So, devmem will access the posioned page and trigger an > exception again, resulting in a synchronous error infinite loop. Such > exception loop may cause platform firmware to exceed some threshold and > reboot when Linux could have recovered from this error. > > To reproduce this problem: > > # STEP 1: inject an UCE error, and kernel will set HWPosion flag for related page > #einj_mem_uc single > 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 > injecting ... > triggering ... > signal 7 code 4 addr 0xffffb0d75000 > page not present > Test passed > > # STEP 2: access the same page and it will trigger a synchronous error infinite loop > devmem 0x4092d55b400 > > To fix above two issues, queue memory_failure() as a task_work so that > it runs in the context of the process that is actually consuming the > poisoned data. > > Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com> > Tested-by: Ma Wupeng <mawupeng1@huawei.com> > Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com> > Reviewed-by: Xiaofei Tan <tanxiaofei@huawei.com> > Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> > Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> > --- > drivers/acpi/apei/ghes.c | 77 +++++++++++++++++++++++----------------- > include/acpi/ghes.h | 3 -- > include/linux/mm.h | 1 - > mm/memory-failure.c | 13 ------- > 4 files changed, 44 insertions(+), 50 deletions(-) > > diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c > index 106486bdfefc..70f2ee3ad1a8 100644 > --- a/drivers/acpi/apei/ghes.c > +++ b/drivers/acpi/apei/ghes.c > @@ -467,28 +467,41 @@ static void ghes_clear_estatus(struct ghes *ghes, > } > > /* The "kernel-doc" format needs an opening "/**". > - * 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 ghes_task_work - for synchronous RAS event > + * > + * @twork: callback_head for task work > + * @pfn: page frame number of corrupted page > + * @flags: work control flags > + * > + * 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 ghes_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; > + struct ghes_task_work *twcb = container_of(twork, struct ghes_task_work, twork); > + int ret; > > - 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("%#llx: Sending SIGBUS to %s:%d due to hardware memory corruption\n", > + twcb->pfn, current->comm, task_pid_nr(current)); This is basically the same as the message in kill_proc(). Was there any consideration to have a shared function? Maybe this could be a future patch. > + force_sig(SIGBUS); > } > > static bool ghes_do_memory_failure(u64 physical_addr, int flags) > { > unsigned long pfn; > + struct ghes_task_work *twcb; Minor nit: A common preference I've seen is to order variable declarations from longest->shortest line length. But overall, looks okay to me. Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com> Thanks, Yazen
在 2024/12/19 00:53, Yazen Ghannam 写道: > On Mon, Dec 02, 2024 at 11:05:27AM +0800, Shuai Xue wrote: >> The memory uncorrected error could be signaled by asynchronous interrupt >> (specifically, SPI in arm64 platform), e.g. when an error is detected by >> a background scrubber, or signaled by synchronous exception >> (specifically, data abort exception in arm64 platform), e.g. when a CPU >> tries to access a poisoned cache line. Currently, both synchronous and >> asynchronous error use memory_failure_queue() to schedule >> memory_failure() to exectute in a kworker context. >> >> As a result, when a user-space process is accessing a poisoned data, a >> data abort is taken and the memory_failure() is executed in the kworker >> context, memory_failure(): >> >> - will send wrong si_code by SIGBUS signal in early_kill mode, and >> - can not kill the user-space in some cases resulting a synchronous >> error infinite loop >> >> Issue 1: send wrong si_code in early_kill mode >> >> 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 is >> expected to terminate the current process which has accessed poisoned >> page. This is done by sending a SIGBUS signal with an error code >> BUS_MCEERR_AR, indicating an action-required machine check error on >> read. >> >> However, when kill_proc() is called to terminate the processes who have >> the poisoned page mapped, it sends the incorrect SIGBUS error code >> BUS_MCEERR_AO because the context in which it operates is not the one >> where the error was triggered. >> >> To reproduce this problem: >> >> #sysctl -w vm.memory_failure_early_kill=1 >> vm.memory_failure_early_kill = 1 >> >> # STEP2: inject an UCE error and consume it to trigger a synchronous error >> #einj_mem_uc single >> 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 >> injecting ... >> triggering ... >> signal 7 code 5 addr 0xffffb0d75000 >> page not present >> Test passed >> >> The si_code (code 5) from einj_mem_uc indicates that it is BUS_MCEERR_AO >> error and it is not the fact. >> >> After this patch: >> >> # STEP1: enable early kill mode >> #sysctl -w vm.memory_failure_early_kill=1 >> vm.memory_failure_early_kill = 1 >> # STEP2: inject an UCE error and consume it to trigger a synchronous error >> #einj_mem_uc single >> 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 >> injecting ... >> triggering ... >> signal 7 code 4 addr 0xffffb0d75000 >> page not present >> Test passed >> >> The si_code (code 4) from einj_mem_uc indicates that it is a BUS_MCEERR_AR >> error as we expected. >> >> Issue 2: a synchronous error infinite loop >> >> If a user-space process, e.g. devmem, accesses a poisoned page for which >> the HWPoison flag is set, kill_accessing_process() is called to send >> SIGBUS to current processs with error info. Because the memory_failure() >> is executed in the kworker context, it will just do nothing but return >> EFAULT. So, devmem will access the posioned page and trigger an >> exception again, resulting in a synchronous error infinite loop. Such >> exception loop may cause platform firmware to exceed some threshold and >> reboot when Linux could have recovered from this error. >> >> To reproduce this problem: >> >> # STEP 1: inject an UCE error, and kernel will set HWPosion flag for related page >> #einj_mem_uc single >> 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 >> injecting ... >> triggering ... >> signal 7 code 4 addr 0xffffb0d75000 >> page not present >> Test passed >> >> # STEP 2: access the same page and it will trigger a synchronous error infinite loop >> devmem 0x4092d55b400 >> >> To fix above two issues, queue memory_failure() as a task_work so that >> it runs in the context of the process that is actually consuming the >> poisoned data. >> >> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com> >> Tested-by: Ma Wupeng <mawupeng1@huawei.com> >> Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com> >> Reviewed-by: Xiaofei Tan <tanxiaofei@huawei.com> >> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> >> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> >> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> >> --- >> drivers/acpi/apei/ghes.c | 77 +++++++++++++++++++++++----------------- >> include/acpi/ghes.h | 3 -- >> include/linux/mm.h | 1 - >> mm/memory-failure.c | 13 ------- >> 4 files changed, 44 insertions(+), 50 deletions(-) >> >> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c >> index 106486bdfefc..70f2ee3ad1a8 100644 >> --- a/drivers/acpi/apei/ghes.c >> +++ b/drivers/acpi/apei/ghes.c >> @@ -467,28 +467,41 @@ static void ghes_clear_estatus(struct ghes *ghes, >> } >> >> /* > > The "kernel-doc" format needs an opening "/**". > >> - * 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 ghes_task_work - for synchronous RAS event >> + * >> + * @twork: callback_head for task work >> + * @pfn: page frame number of corrupted page >> + * @flags: work control flags >> + * >> + * 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 ghes_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; >> + struct ghes_task_work *twcb = container_of(twork, struct ghes_task_work, twork); >> + int ret; >> >> - 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("%#llx: Sending SIGBUS to %s:%d due to hardware memory corruption\n", >> + twcb->pfn, current->comm, task_pid_nr(current)); > > This is basically the same as the message in kill_proc(). Was there any > consideration to have a shared function? Maybe this could be a future > patch. Yep, I'd like to refactor in a future. > >> + force_sig(SIGBUS); >> } >> >> static bool ghes_do_memory_failure(u64 physical_addr, int flags) >> { >> unsigned long pfn; >> + struct ghes_task_work *twcb; > > Minor nit: A common preference I've seen is to order variable > declarations from longest->shortest line length. Will fix it if this patch set still misses the next merge window. > > But overall, looks okay to me. > > Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com> > > Thanks, > Yazen Thanks for valuable comments. Best Regards, Shuai
diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c index 106486bdfefc..70f2ee3ad1a8 100644 --- a/drivers/acpi/apei/ghes.c +++ b/drivers/acpi/apei/ghes.c @@ -467,28 +467,41 @@ 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 ghes_task_work - for synchronous RAS event + * + * @twork: callback_head for task work + * @pfn: page frame number of corrupted page + * @flags: work control flags + * + * 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 ghes_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; + struct ghes_task_work *twcb = container_of(twork, struct ghes_task_work, twork); + int ret; - 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("%#llx: Sending SIGBUS to %s:%d due to hardware memory corruption\n", + twcb->pfn, current->comm, task_pid_nr(current)); + force_sig(SIGBUS); } static bool ghes_do_memory_failure(u64 physical_addr, int flags) { unsigned long pfn; + struct ghes_task_work *twcb; if (!IS_ENABLED(CONFIG_ACPI_APEI_MEMORY_FAILURE)) return false; @@ -501,6 +514,18 @@ 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; } @@ -745,7 +770,7 @@ int cxl_cper_kfifo_get(struct cxl_cper_work_data *wd) } EXPORT_SYMBOL_NS_GPL(cxl_cper_kfifo_get, 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; @@ -811,8 +836,6 @@ static bool ghes_do_proc(struct ghes *ghes, current->comm, task_pid_nr(current)); force_sig(SIGBUS); } - - return queued; } static void __ghes_print_estatus(const char *pfx, @@ -1114,9 +1137,7 @@ 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); /* @@ -1131,25 +1152,16 @@ 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); + gen_pool_free(ghes_estatus_pool, (unsigned long)estatus_node, + node_len); llnode = next; } @@ -1210,7 +1222,6 @@ 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 be1dd4c1a917..ebd21b05fe6e 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/include/linux/mm.h b/include/linux/mm.h index c39c4945946c..aa4246c7c23e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3936,7 +3936,6 @@ enum mf_flags { int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index, unsigned long count, int mf_flags); extern int memory_failure(unsigned long pfn, int flags); -extern void memory_failure_queue_kick(int cpu); extern int unpoison_memory(unsigned long pfn); extern atomic_long_t num_poisoned_pages __read_mostly; extern int soft_offline_page(unsigned long pfn, int flags); diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 14c316d7d38d..e0adb665d07b 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -2499,19 +2499,6 @@ 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;
The memory uncorrected error could be signaled by asynchronous interrupt (specifically, SPI in arm64 platform), e.g. when an error is detected by a background scrubber, or signaled by synchronous exception (specifically, data abort exception in arm64 platform), e.g. when a CPU tries to access a poisoned cache line. Currently, both synchronous and asynchronous error use memory_failure_queue() to schedule memory_failure() to exectute in a kworker context. As a result, when a user-space process is accessing a poisoned data, a data abort is taken and the memory_failure() is executed in the kworker context, memory_failure(): - will send wrong si_code by SIGBUS signal in early_kill mode, and - can not kill the user-space in some cases resulting a synchronous error infinite loop Issue 1: send wrong si_code in early_kill mode 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 is expected to terminate the current process which has accessed poisoned page. This is done by sending a SIGBUS signal with an error code BUS_MCEERR_AR, indicating an action-required machine check error on read. However, when kill_proc() is called to terminate the processes who have the poisoned page mapped, it sends the incorrect SIGBUS error code BUS_MCEERR_AO because the context in which it operates is not the one where the error was triggered. To reproduce this problem: #sysctl -w vm.memory_failure_early_kill=1 vm.memory_failure_early_kill = 1 # STEP2: inject an UCE error and consume it to trigger a synchronous error #einj_mem_uc single 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 injecting ... triggering ... signal 7 code 5 addr 0xffffb0d75000 page not present Test passed The si_code (code 5) from einj_mem_uc indicates that it is BUS_MCEERR_AO error and it is not the fact. After this patch: # STEP1: enable early kill mode #sysctl -w vm.memory_failure_early_kill=1 vm.memory_failure_early_kill = 1 # STEP2: inject an UCE error and consume it to trigger a synchronous error #einj_mem_uc single 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 injecting ... triggering ... signal 7 code 4 addr 0xffffb0d75000 page not present Test passed The si_code (code 4) from einj_mem_uc indicates that it is a BUS_MCEERR_AR error as we expected. Issue 2: a synchronous error infinite loop If a user-space process, e.g. devmem, accesses a poisoned page for which the HWPoison flag is set, kill_accessing_process() is called to send SIGBUS to current processs with error info. Because the memory_failure() is executed in the kworker context, it will just do nothing but return EFAULT. So, devmem will access the posioned page and trigger an exception again, resulting in a synchronous error infinite loop. Such exception loop may cause platform firmware to exceed some threshold and reboot when Linux could have recovered from this error. To reproduce this problem: # STEP 1: inject an UCE error, and kernel will set HWPosion flag for related page #einj_mem_uc single 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 injecting ... triggering ... signal 7 code 4 addr 0xffffb0d75000 page not present Test passed # STEP 2: access the same page and it will trigger a synchronous error infinite loop devmem 0x4092d55b400 To fix above two issues, queue memory_failure() as a task_work so that it runs in the context of the process that is actually consuming the poisoned data. Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com> Tested-by: Ma Wupeng <mawupeng1@huawei.com> Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com> Reviewed-by: Xiaofei Tan <tanxiaofei@huawei.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> --- drivers/acpi/apei/ghes.c | 77 +++++++++++++++++++++++----------------- include/acpi/ghes.h | 3 -- include/linux/mm.h | 1 - mm/memory-failure.c | 13 ------- 4 files changed, 44 insertions(+), 50 deletions(-)