x86/acpi: Warn about multiple HPET tables

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Tim Deegan <tim@xen.org>

diff --git a/xen/arch/x86/acpi/boot.c b/xen/arch/x86/acpi/boot.c
index df264233cd2995a784e6b9dc917f3268010b4511..6d7984ffda3dce66189e50288ebebeda140dc185 100644 (file)
--- a/xen/arch/x86/acpi/boot.c
+++ b/xen/arch/x86/acpi/boot.c
@@ -289,6 +289,22 @@ static int __init acpi_parse_hpet(struct acpi_table_header *table)
                return -1;
        }
 
+       /*
+        * Some BIOSes provide multiple HPET tables.  Sometimes this is a BIOS
+        * bug; the intended way of supporting more than 1 HPET is to use AML
+        * entries.
+        *
+        * If someone finds a real system with two genuine HPET tables, perhaps
+        * they will be kind and implement support.  Until then however, warn
+        * that we will ignore subsequent tables.
+        */
+       if (hpet_address)
+       {
+               printk(KERN_WARNING PREFIX
+                      "Found multiple HPET tables. Only using first\n");
+               return -1;
+       }
+
        hpet_address = hpet_tbl->address.address;
        hpet_blockid = hpet_tbl->sequence;
        printk(KERN_INFO PREFIX "HPET id: %#x base: %#lx\n",