[PATCH] x86/cet: Support cet=<bool> on the command line

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

... as a shorthand for setting both suboptions at once.

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>

I think this wants backporting.  cet=0 is "so obviously" the way to turn off
both that I tried using it to debug a problem.  It's absence was an oversight
of the original CET logic.
---
 docs/misc/xen-command-line.pandoc |  4 +++-
 xen/arch/x86/setup.c              | 15 ++++++++++++++-
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/docs/misc/xen-command-line.pandoc 
b/docs/misc/xen-command-line.pandoc
index 1dc7e1ca0706..1720cb216824 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -271,7 +271,7 @@ enough. Setting this to a high value may cause boot 
failure, particularly if
 the NMI watchdog is also enabled.
 
 ### cet
-    = List of [ shstk=<bool>, ibt=<bool> ]
+    = List of [ <bool>, shstk=<bool>, ibt=<bool> ]
 
     Applicability: x86
 
@@ -283,6 +283,8 @@ CET is incompatible with 32bit PV guests.  If any CET 
sub-options are active,
 they will override the `pv=32` boolean to `false`.  Backwards compatibility
 can be maintained with the pv-shim mechanism.
 
+*   An unqualified boolean is shorthand for setting all suboptions at once.
+
 *   The `shstk=` boolean controls whether Xen uses Shadow Stacks for its own
     protection.
 
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 53a73010e029..090abfd71754 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -117,7 +117,20 @@ static int __init cf_check parse_cet(const char *s)
         if ( !ss )
             ss = strchr(s, '\0');
 
-        if ( (val = parse_boolean("shstk", s, ss)) >= 0 )
+        if ( (val = parse_bool(s, ss)) >= 0 )
+        {
+#ifdef CONFIG_XEN_SHSTK
+            opt_xen_shstk = val;
+#else
+            no_config_param("XEN_SHSTK", "cet", s, ss);
+#endif
+#ifdef CONFIG_XEN_IBT
+            opt_xen_ibt = val;
+#else
+            no_config_param("XEN_IBT", "cet", s, ss);
+#endif
+        }
+        else if ( (val = parse_boolean("shstk", s, ss)) >= 0 )
         {
 #ifdef CONFIG_XEN_SHSTK
             opt_xen_shstk = val;
-- 
2.11.0