xen: [v2] 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>

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index b49256d..8c307c9 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=") )
+        {
+            char acpi_os_root_pointer_string[MAX_RSDP_ADDRESS_STRING];
+            int acpi_os_root_pointer_string_size = snprintf(acpi_os_root_pointer_string, 
+                                                            MAX_RSDP_ADDRESS_STRING, "%08lX", 
+                                                            acpi_os_get_root_pointer());
+
+            if ( (acpi_os_root_pointer_string_size > 0) && (acpi_os_root_pointer_string_size <= MAX_RSDP_ADDRESS_STRING) )
+            {   
+                safe_strcat(dom0_cmdline, " acpi_rsdp=0x");
+                safe_strcat(dom0_cmdline, acpi_os_root_pointer_string);
+            } 
+            else 
+            {
+                printk(XENLOG_WARNING "RSDP Address String Size Check Failed!\n");
+                printk(XENLOG_WARNING "Not passing acpi_rsdp to Dom0!\n");
+                printk(XENLOG_WARNING "(Expected size 1-%d, got %d)\n", MAX_RSDP_ADDRESS_STRING, acpi_os_root_pointer_string_size);
+            }
+        }
 
         cmdline = dom0_cmdline;
     }
diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
index 8c5697e..a7c3905 100644
--- a/xen/include/public/xen.h
+++ b/xen/include/public/xen.h
@@ -750,6 +750,7 @@ struct start_info {
                                 /*  SIF_MOD_START_PFN set in flags).      */
     unsigned long mod_len;      /* Size (bytes) of pre-loaded module.     */
 #define MAX_GUEST_CMDLINE 1024
+#define MAX_RSDP_ADDRESS_STRING 21
     int8_t cmd_line[MAX_GUEST_CMDLINE];
     /* The pfn range here covers both page table and p->m table frames.   */
     unsigned long first_p2m_pfn;/* 1st pfn forming initial P->M table.    */