This is a note to let you know that I've just added the patch titled
ACPI/APEI: Limit printable size of BERT table data
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
acpi-apei-limit-printable-size-of-bert-table-data.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 29007555711604bb682c22ba38a2962c2724582f
Author: Darren Hart <darren@xxxxxxxxxxxxxxxxxxxxxx>
Date: Tue Mar 8 10:50:48 2022 -0800
ACPI/APEI: Limit printable size of BERT table data
[ 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@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/acpi/apei/bert.c b/drivers/acpi/apei/bert.c
index 86211422f4ee..598fd19b65fa 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,
