x86/mce: Provide boot argument to honour bios-set CMCI threshold

The ACPI spec doesn't provide for a way for the bios to pass down
recommended thresholds to the OS on a _per-bank_ basis. This patch adds
a new boot option, which if passed, tells Linux to use CMCI thresholds
set by the bios.

As fail-safe, we initialize threshold to 1 if some banks have not been
initialized by the bios and warn the user.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/Documentation/x86/x86_64/boot-options.txt b/Documentation/x86/x86_64/boot-options.txt
index c54b4f503e2a..de38429beb71 100644
--- a/Documentation/x86/x86_64/boot-options.txt
+++ b/Documentation/x86/x86_64/boot-options.txt
@@ -50,6 +50,13 @@ Machine check
                 monarchtimeout:
                 Sets the time in us to wait for other CPUs on machine checks. 0
                 to disable.
+   mce=bios_cmci_threshold
+                Don't overwrite the bios-set CMCI threshold. This boot option
+                prevents Linux from overwriting the CMCI threshold set by the
+                bios. Without this option, Linux always sets the CMCI
+                threshold to 1. Enabling this may make memory predictive failure
+                analysis less effective if the bios sets thresholds for memory
+                errors since we will not see details for all errors.
 
    nomce (for compatibility with i386): same as mce=off