powerpc: Document xive=off option

commit 243e25112d06 ("powerpc/xive: Native exploitation of the XIVE
interrupt controller") added an option to turn off Linux native XIVE
usage via the xive=off kernel command line option.

This documents this option.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Acked-by: Stewart Smith <stewart@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index a4c3538..7b15abf 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5272,6 +5272,15 @@
                        Format:
                        <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
 
+       xive=           [PPC]
+                       By default on POWER9 and above, the kernel will
+                       natively use the XIVE interrupt controller. This option
+                       allows the fallback firmware mode to be used:
+
+                       off       Fallback to firmware control of XIVE interrupt
+                                 controller on both pseries and powernv
+                                 platforms. Only useful on POWER9 and above.
+
        xhci-hcd.quirks         [USB,KNL]
                        A hex value specifying bitmask with supplemental xhci
                        host controller quirks. Meaning of each bit can be