From: Darren Hart darren@os.amperecomputing.com
[ Upstream commit 3f8dec116210ca649163574ed5f8df1e3b837d07 ]
Platforms with large BERT table data can trigger soft lockup errors while attempting to print the entire BERT table data to the console at boot:
watchdog: BUG: soft lockup - CPU#160 stuck for 23s! [swapper/0:1]
Observed on Ampere Altra systems with a single BERT record of ~250KB.
The original bert driver appears to have assumed relatively small table data. Since it is impractical to reassemble large table data from interwoven console messages, and the table data is available in
/sys/firmware/acpi/tables/data/BERT
limit the size for tables printed to the console to 1024 (for no reason other than it seemed like a good place to kick off the discussion, would appreciate feedback from existing users in terms of what size would maintain their current usage model).
Alternatively, we could make printing a CONFIG option, use the bert_disable boot arg (or something similar), or use a debug log level. However, all those solutions require extra steps or change the existing behavior for small table data. Limiting the size preserves existing behavior on existing platforms with small table data, and eliminates the soft lockups for platforms with large table data, while still making it available.
Signed-off-by: Darren Hart darren@os.amperecomputing.com Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/acpi/apei/bert.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/acpi/apei/bert.c b/drivers/acpi/apei/bert.c index 08d820c04618..76b7539a37a9 100644 --- a/drivers/acpi/apei/bert.c +++ b/drivers/acpi/apei/bert.c @@ -29,6 +29,7 @@
#undef pr_fmt #define pr_fmt(fmt) "BERT: " fmt +#define ACPI_BERT_PRINT_MAX_LEN 1024
static int bert_disable;
@@ -58,8 +59,11 @@ static void __init bert_print_all(struct acpi_bert_region *region, }
pr_info_once("Error records from previous boot:\n"); - - cper_estatus_print(KERN_INFO HW_ERR, estatus); + if (region_len < ACPI_BERT_PRINT_MAX_LEN) + cper_estatus_print(KERN_INFO HW_ERR, estatus); + else + pr_info_once("Max print length exceeded, table data is available at:\n" + "/sys/firmware/acpi/tables/data/BERT");
/* * Because the boot error source is "one-time polled" type,