For no good reason I had assumed that ACPI table headers would be page

aligned (or at least not cross a page boundary).  However, it turns out
that on at least one machine one table header does cross a page boundary.
This caused problems with the MADT early probe as it uses the crash dump
map to load ACPI tables by loading the RSDT/XSDT into pages 1 ... N and
loading the header of each ACPI table header into page 0 looking for the
MADT.  However, if a table header crossed a page boundary, then page 1
would get trashed resulting in a panic.  Fix this by reserving the first
2 pages for ACPI table headers (headers are less than a page in size,
so 2 pages will be sufficient) and use pages 2 .. N for the RSDT and XSDT.

Note: amd64 should probably be simplified to just use pmap_mapbios()
for all these tables which will use the direct map and not need the
crash dump hack.

MFC after:	5 days
Tested on:	i386
Reported by:	Pete French  petefrench of ticketswitch.com

1 files changed, 7 insertions, 5 deletions

diff --git a/sys/amd64/acpica/madt.c b/sys/amd64/acpica/madt.c
index fcd40c8..3ed1ea7 100644
--- a/sys/amd64/acpica/madt.c
+++ b/sys/amd64/acpica/madt.c
@@ -109,9 +109,11 @@ static struct apic_enumerator madt_enumerator = {
 /*
  * Code to abuse the crashdump map to map in the tables for the early
  * probe.  We cheat and make the following assumptions about how we
- * use this KVA: page 0 is used to map in the first page of each table
- * found via the RSDT or XSDT and pages 1 to n are used to map in the
- * RSDT or XSDT.  The offset is in pages; the length is in bytes.
+ * use this KVA: pages 0 and 1 are used to map in the header of each
+ * table found via the RSDT or XSDT and pages 2 to n are used to map
+ * in the RSDT or XSDT.  We have to use 2 pages for the table headers
+ * in case a header spans a page boundary.  The offset is in pages;
+ * the length is in bytes.
  */
 static void *
 madt_map(vm_paddr_t pa, int offset, vm_offset_t length)
@@ -232,7 +234,7 @@ madt_probe(void)
 				printf("MADT: RSDP failed extended checksum\n");
 			return (ENXIO);
 		}
-		xsdt = madt_map_table(rsdp->XsdtPhysicalAddress, 1,
+		xsdt = madt_map_table(rsdp->XsdtPhysicalAddress, 2,
 		    ACPI_SIG_XSDT);
 		if (xsdt == NULL) {
 			if (bootverbose)
@@ -246,7 +248,7 @@ madt_probe(void)
 				break;
 		madt_unmap_table(xsdt);
 	} else {
-		rsdt = madt_map_table(rsdp->RsdtPhysicalAddress, 1,
+		rsdt = madt_map_table(rsdp->RsdtPhysicalAddress, 2,
 		    ACPI_SIG_RSDT);
 		if (rsdt == NULL) {
 			if (bootverbose)