[PATCH 1/3] x86/acpi: Warn about multiple HPET tables

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

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Keir Fraser <keir@xen.org>
CC: Jan Beulich <JBeulich@suse.com>
---
 xen/arch/x86/acpi/boot.c |   16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/xen/arch/x86/acpi/boot.c b/xen/arch/x86/acpi/boot.c
index df26423..ccbe918 100644
--- 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",
-- 
1.7.10.4