[PATCH for-4.18] docs: Fix IOMMU command line docs some more

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Make the command line docs match the actual implementation, and state that the
default behaviour is selected at compile time.

Fixes: 980d6acf1517 ("IOMMU: make DMA containment of quarantined devices 
optional")
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
CC: Henry Wang <Henry.Wang@xxxxxxx>
---
 docs/misc/xen-command-line.pandoc | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/docs/misc/xen-command-line.pandoc 
b/docs/misc/xen-command-line.pandoc
index 6b07d0f3a17f..9a19a04157cb 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -1480,7 +1480,8 @@ detection of systems known to misbehave upon accesses to 
that port.
 > Default: `new` unless directed-EOI is supported
 
 ### iommu
-    = List of [ <bool>, verbose, debug, force, required, 
quarantine[=scratch-page],
+    = List of [ <bool>, verbose, debug, force, required,
+                quarantine=<bool>|scratch-page,
                 sharept, superpages, intremap, intpost, crash-disable,
                 snoop, qinval, igfx, amd-iommu-perdev-intremap,
                 dom0-{passthrough,strict} ]
@@ -1519,7 +1520,8 @@ boolean (e.g. `iommu=no`) can override this and leave the 
IOMMUs disabled.
     successfully.
 
 *   The `quarantine` option can be used to control Xen's behavior when
-    de-assigning devices from guests.
+    de-assigning devices from guests.  The default behaviour is chosen at
+    compile time, and is one of 
`CONFIG_IOMMU_QUARANTINE_{NONE,BASIC,SCRATCH_PAGE}`.
 
     When a PCI device is assigned to an untrusted domain, it is possible
     for that domain to program the device to DMA to an arbitrary address.

base-commit: 9659b2a6d73b14620e187f9c626a09323853c459
-- 
2.30.2