[PATCH v3 4/7] docs: Improve documentation and parsing for efi=

[Andrew Cooper <andrew.cooper3@citrix.com>]

Update parse_efi_param() to use parse_boolean() for "rs", so it behaves
like other Xen booleans.

However, change "attr=uc" to not be a boolean.  This is a functional
change, but "no-attr=uc" is ambiguous and shouldn't be accepted.

Update the command line documentation for consistency.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Juergen Gross <jgross@suse.com>

v3:
 * New
---
 docs/misc/xen-command-line.pandoc | 22 ++++++++--------------
 xen/common/efi/boot.c             | 11 +++--------
 2 files changed, 11 insertions(+), 22 deletions(-)

diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc
index 41dec5b..4f27e54 100644
--- a/docs/misc/xen-command-line.pandoc
+++ b/docs/misc/xen-command-line.pandoc
@@ -851,23 +851,17 @@ disable it (edid=no). This option should not normally be required
 except for debugging purposes.
 
 ### efi
-> `= List of [ rs | attr ]`
+> `= List of [ rs=<bool>, attr=uc ]`
 
-All options are of boolean kind and can be prefixed with `no-` to
-effect the inverse meaning.
+Controls for interacting with the system Extended Firmware Interface.
 
-> `rs`
+*   The `rs` boolean controls whether Runtime Services are used.  By default,
+    Xen uses Runtime Services itself, and proxies certain calls on behalf of
+    dom0.  Selecting `rs=0` prohibits all use of Runtime Services.
 
-> Default: `true`
-
->> Force or disable use of EFI runtime services.
-
-> `attr=uc`
-
-> Default: `off`
-
->> Allows mapping of RuntimeServices which have no cachability attribute
->> set as UC.
+*   The `attr=uc` string exists as a workaround, to allow mapping memory regions
+    with unknown/unrecognised cacheability as uncacheable, rather than not
+    present.
 
 ### ept
 > `= List of [ ad=<bool>, pml=<bool> ]`
diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index 1e1a551..597b2ff 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -1389,19 +1389,14 @@ static bool __initdata efi_map_uc;
 static int __init parse_efi_param(const char *s)
 {
     const char *ss;
-    int rc = 0;
+    int rc = 0, val;
 
     do {
-        bool val = strncmp(s, "no-", 3);
-
-        if ( !val )
-            s += 3;
-
         ss = strchr(s, ',');
         if ( !ss )
             ss = strchr(s, '\0');
 
-        if ( !cmdline_strcmp(s, "rs") )
+        if ( (val = parse_boolean("rs", s, ss)) >= 0 )
         {
             if ( val )
                 __set_bit(EFI_RS, &efi_flags);
@@ -1409,7 +1404,7 @@ static int __init parse_efi_param(const char *s)
                 __clear_bit(EFI_RS, &efi_flags);
         }
         else if ( !cmdline_strcmp(s, "attr=uc") )
-            efi_map_uc = val;
+            efi_map_uc = true;
         else
             rc = -EINVAL;
 
-- 
2.1.4


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