ACPI: acpi_enforce_resource=strict by default

Enforce strict resource checking - disallowing access by native
drivers to IO ports and memory regions claimed by ACPI firmware.

The patch is mainly aimed to block native hwmon drivers from touching
monitoring chips that ACPI thinks it own.

If this causes a regression, boot with "acpi_enforce_resources=lax"
which was the previous default.

http://bugzilla.kernel.org/show_bug.cgi?id=12376
http://bugzilla.kernel.org/show_bug.cgi?id=12541

Signed-off-by: Luca Tettamanti <kronos.it@gmail.com>
Acked-by: Pavel Machek <pavel@suse.cz>
Acked-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 54f21a5c262b..7068d0bc47c5 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -258,6 +258,22 @@ and is between 256 and 4096 characters. It is defined in the file
                         to assume that this machine's pmtimer latches its value
                         and always returns good values.
 
+        acpi_enforce_resources= [ACPI]
+                        { strict | lax | no }
+                        Check for resource conflicts between native drivers
+                        and ACPI OperationRegions (SystemIO and SystemMemory
+                        only). IO ports and memory declared in ACPI might be
+                        used by the ACPI subsystem in arbitrary AML code and
+                        can interfere with legacy drivers.
+                        strict (default): access to resources claimed by ACPI
+                        is denied; legacy drivers trying to access reserved
+                        resources will fail to bind to device using them.
+                        lax: access to resources claimed by ACPI is allowed;
+                        legacy drivers trying to access reserved resources
+                        will bind successfully but a warning message is logged.
+                        no: ACPI OperationRegions are not marked as reserved,
+                        no further checks are performed.
+
         agp=            [AGP]
                         { off | try_unsupported }
                         off: disable AGP support