AMD IOMMU: allow command line overrides for broken IVRS tables

With there being so many systems with broken ACPI tables, and with it
generally being known what's wrong with those tables, give people a
handle to overcome the resulting disabling of their IOMMUs.

Inspired by Linux side patches providing similar functionality.

Suggested-by: Sander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Tested-By: Sander Eikelenboom <linux@eikelenboom.it>
Acked-by: Keir Fraser <keir@xen.org>
Acked-by: Suravee Suthikulpanit <suravee.suthikulapanit@amd.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/xen/common/kernel.c b/xen/common/kernel.c
index 72fb9055b1..b8707d90a1 100644
--- a/xen/common/kernel.c
+++ b/xen/common/kernel.c
@@ -81,9 +81,15 @@ void __init cmdline_parse(const char *cmdline)
         /* Search for value part of a key=value option. */
         optval = strchr(opt, '=');
         if ( optval != NULL )
+        {
             *optval++ = '\0'; /* nul-terminate the option value */
+            q = strpbrk(opt, "([{<");
+        }
         else
+        {
             optval = q;       /* default option value is empty string */
+            q = NULL;
+        }
 
         /* Boolean parameters can be inverted with 'no-' prefix. */
         bool_assert = !!strncmp("no-", optkey, 3);
@@ -93,7 +99,17 @@ void __init cmdline_parse(const char *cmdline)
         for ( param = &__setup_start; param < &__setup_end; param++ )
         {
             if ( strcmp(param->name, optkey) )
+            {
+                if ( param->type == OPT_CUSTOM && q &&
+                     strlen(param->name) == q + 1 - opt &&
+                     !strncmp(param->name, opt, q + 1 - opt) )
+                {
+                    optval[-1] = '=';
+                    ((void (*)(const char *))param->var)(q);
+                    optval[-1] = '\0';
+                }
                 continue;
+            }
 
             switch ( param->type )
             {