Re: [PATCH v5 1/2] ACPI: APEI: set memory failure flags as MF_ACTION_REQUIRED on synchronous events

[Kefeng Wang]

Hi Shuai Xue，

On 2023/4/11 18:48, Shuai Xue wrote:
> There are two major types of uncorrected recoverable (UCR) errors :
>
> - 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.
>
> 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 this end, set memory failure flags as MF_ACTION_REQUIRED on synchronous
> events.

As your mentioned in cover-letter, we met same issue, and hope it could 
be fixed ASAP, this patch looks good to me,

Reviewed-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>


> Fixes: ba61ca4aab47 ("ACPI, APEI, GHES: Add hardware memory error recovery support")'
> Signed-off-by: Shuai Xue <xueshuai@xxxxxxxxxxxxxxxxx>
> Tested-by: Ma Wupeng <mawupeng1@xxxxxxxxxx>
> ---
>   drivers/acpi/apei/ghes.c | 29 +++++++++++++++++++++++------
>   1 file changed, 23 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index 34ad071a64e9..c479b85899f5 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;
> +}
> +
>   /*
>    * This driver isn't really modular, however for the time being,
>    * continuing to use module_param is the easiest way to remain
> @@ -477,7 +491,7 @@ static bool ghes_do_memory_failure(u64 physical_addr, int flags)
>   }
>   
>   static bool ghes_handle_memory_failure(struct acpi_hest_generic_data *gdata,
> -				       int sev)
> +				       int sev, bool sync)
>   {
>   	int flags = -1;
>   	int sec_sev = ghes_severity(gdata->error_severity);
> @@ -491,7 +505,7 @@ static bool ghes_handle_memory_failure(struct acpi_hest_generic_data *gdata,
>   	    (gdata->flags & CPER_SEC_ERROR_THRESHOLD_EXCEEDED))
>   		flags = MF_SOFT_OFFLINE;
>   	if (sev == GHES_SEV_RECOVERABLE && sec_sev == GHES_SEV_RECOVERABLE)
> -		flags = 0;
> +		flags = sync ? MF_ACTION_REQUIRED : 0;
>   
>   	if (flags != -1)
>   		return ghes_do_memory_failure(mem_err->physical_addr, flags);
> @@ -499,9 +513,11 @@ static bool ghes_handle_memory_failure(struct acpi_hest_generic_data *gdata,
>   	return false;
>   }
>   
> -static bool ghes_handle_arm_hw_error(struct acpi_hest_generic_data *gdata, int sev)
> +static bool 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);
> +	int flags = sync ? MF_ACTION_REQUIRED : 0;
>   	bool queued = false;
>   	int sec_sev, i;
>   	char *p;
> @@ -526,7 +542,7 @@ static bool ghes_handle_arm_hw_error(struct acpi_hest_generic_data *gdata, int s
>   		 * and don't filter out 'corrected' error here.
>   		 */
>   		if (is_cache && has_pa) {
> -			queued = ghes_do_memory_failure(err_info->physical_fault_addr, 0);
> +			queued = ghes_do_memory_failure(err_info->physical_fault_addr, flags);
>   			p += err_info->length;
>   			continue;
>   		}
> @@ -647,6 +663,7 @@ static bool ghes_do_proc(struct ghes *ghes,
>   	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);
>   	apei_estatus_for_each_section(estatus, gdata) {
> @@ -664,13 +681,13 @@ 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);
> +			queued = 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);
> +			queued = ghes_handle_arm_hw_error(gdata, sev, sync);
>   		} else {
>   			void *err = acpi_hest_get_payload(gdata);
>