ACPI/APEI is designed to verifiy/report H/W errors, like Corrected
Error(CE) and Uncorrected Error(UC). It contains four tables: HEST,
ERST, EINJ and BERT. The first three tables have been merged for
a long time, but because of lacking BIOS support for BERT, the
support for BERT is pending until now. Recently on ARM 64 platform
it is has been supported. So here we come.

Under normal circumstances, when a hardware error occurs, kernel will
be notified via NMI, MCE or some other method, then kernel will
process the error condition, report it, and recover it if possible.
But sometime, the situation is so bad, so that firmware may choose to
reset directly without notifying Linux kernel.

Linux kernel can use the Boot Error Record Table (BERT) to get the
un-notified hardware errors that occurred in a previous boot. In this
patch, the error information is reported via printk.

For more information about BERT, please refer to ACPI Specification
version 6.0, section 18.3.1:
  http://www.uefi.org/sites/default/files/resources/ACPI_6.0.pdf

The following log is a BERT record after system reboot because of hitting
a fatal memory error:
BERT: Error records from previous boot:
[Hardware Error]: It has been corrected by h/w and requires no further action
[Hardware Error]: event severity: corrected
[Hardware Error]:  Error 0, type: recoverable
[Hardware Error]:   section_type: memory error
[Hardware Error]:   error_status: 0x0000000000000400
[Hardware Error]:   physical_address: 0xffffffffffffffff
[Hardware Error]:   card: 1 module: 2 bank: 3 row: 1 column: 2 bit_position: 5
[Hardware Error]:   error_type: 2, single-bit ECC

[Tomasz Nowicki: Clear error status at the end of error handling]
[Tony: Applied some cleanups suggested by Fu Wei]
[Fu Wei: delete EXPORT_SYMBOL_GPL(bert_disable), improve the code]
Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Tomasz Nowicki <tomasz.nowicki@linaro.org>
Signed-off-by: Chen, Gong <gong.chen@linux.intel.com>
Tested-by: Jonathan (Zhixiong) Zhang <zjzhang@codeaurora.org>
Signed-off-by: Fu Wei <fu.wei@linaro.org>
Tested-by: Tyler Baicar <tbaicar@codeaurora.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>