ACPI/APEI: Limit printable size of BERT table data

ACPI/APEI: Limit printable size of BERT table data

BugLink: https://bugs.launchpad.net/bugs/1969110
[ 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>
(cherry picked from commit c02f2d420a4434444d62b462ffeec05186443f4c)
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>