xen: [v3] Pass the location of the ACPI RSDP to DOM0.
 
Some machines, such as recent IBM servers, only allow the OS to get the
ACPI RSDP from EFI. Since Xen nukes DOM0's ability to access EFI, DOM0
cannot get the RSDP on these machines, leading to all sorts of
functionality reductions.
 
Signed-off-by: Philip Wernersbach <philip.wernersbach@xxxxxxxxx>

---
Changed since v2:
    * Fix coding style
    * Get rid of extra define
    * Use correct typedef'd type for the ACPI RSDP pointer
    * Better error checking conditional
    * Simplify error message

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index b49256d..fdeb9f2 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1378,6 +1378,25 @@ void __init __start_xen(unsigned long mbi_p)
             safe_strcat(dom0_cmdline, " acpi=");
             safe_strcat(dom0_cmdline, acpi_param);
         }
+        if ( !strstr(dom0_cmdline, "acpi_rsdp=") )
+        {
+            acpi_physical_address rp = acpi_os_get_root_pointer();
+            char rp_str[sizeof(acpi_physical_address)*2 + 1];
+
+            if ( rp )
+            {
+                snprintf(rp_str, sizeof(acpi_physical_address)*2 + 1,
+                         "%08lX", rp);
+
+                safe_strcat(dom0_cmdline, " acpi_rsdp=0x");
+                safe_strcat(dom0_cmdline, rp_str);
+            }
+            else
+            {
+                printk(XENLOG_WARNING 
+                       "Failed to get acpi_rsdp to pass to dom0\n");
+            }
+        }
 
         cmdline = dom0_cmdline;
     }