x86/apic: Update the 'apic=' description of setting APIC driver

There are two consumers of apic=: the APIC debug level and the low
level generic architecture code, but Linux just documented the first
one.

Append the second description.

Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Cc: rdunlap@infradead.org
Cc: corbet@lwn.net
Link: https://lkml.kernel.org/r/20171204040313.24824-2-douly.fnst@cn.fujitsu.com

1 files changed, 5 insertions, 1 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index b74e13312fdc..852fb11dd2c9 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -328,11 +328,15 @@
                         not play well with APC CPU idle - disable it if you have
                         APC and your system crashes randomly.
 
-        apic=           [APIC,X86-32] Advanced Programmable Interrupt Controller
+        apic=           [APIC,X86] Advanced Programmable Interrupt Controller
                         Change the output verbosity whilst booting
                         Format: { quiet (default) | verbose | debug }
                         Change the amount of debugging information output
                         when initialising the APIC and IO-APIC components.
+                        For X86-32, this can also be used to specify an APIC
+                        driver name.
+                        Format: apic=driver_name
+                        Examples: apic=bigsmp
 
         apic_extnmi=    [APIC,X86] External NMI delivery setting
                         Format: { bsp (default) | all | none }