[PATCH] generalise mptable access

arch/i386/kernel/mpparse.c

@@ -33,6 +33,7 @@
 
 #include <mach_apic.h>
 #include <mach_mpparse.h>
+#include <bios_ebda.h>
 
 /* Have we found an MP table */
 int smp_found_config;
@@ -708,8 +709,23 @@ static int __init smp_scan_config (unsigned long base, unsigned long length)
 			printk(KERN_INFO "found SMP MP-table at %08lx\n",
 						virt_to_phys(mpf));
 			reserve_bootmem(virt_to_phys(mpf), PAGE_SIZE);
-			if (mpf->mpf_physptr)
-				reserve_bootmem(mpf->mpf_physptr, PAGE_SIZE);
+			if (mpf->mpf_physptr) {
+				/*
+				 * We cannot access to MPC table to compute
+				 * table size yet, as only few megabytes from
+				 * the bottom is mapped now.
+				 * PC-9800's MPC table places on the very last
+				 * of physical memory; so that simply reserving
+				 * PAGE_SIZE from mpg->mpf_physptr yields BUG()
+				 * in reserve_bootmem.
+				 */
+				unsigned long size = PAGE_SIZE;
+				unsigned long end = max_low_pfn * PAGE_SIZE;
+				if (mpf->mpf_physptr + size > end)
+					size = end - mpf->mpf_physptr;
+				reserve_bootmem(mpf->mpf_physptr, size);
+			}
+
 			mpf_found = mpf;
 			return 1;
 		}
@@ -752,9 +768,9 @@ void __init find_smp_config (void)
 	 * MP1.4 SPEC states to only scan first 1K of 4K EBDA.
 	 */
 
-	address = *(unsigned short *)phys_to_virt(0x40E);
-	address <<= 4;
-	smp_scan_config(address, 0x400);
+	address = get_bios_ebda();
+	if (address)
+		smp_scan_config(address, 0x400);
 }