[PATCH] x86_64: Always use CPUID 80000008 to figure out MTRR address space size

It doesn't make sense to only do this only for AMD K8.

This would support future CPUs with extended address spaces properly.

For i386 and x86-64

Cc: <davej@redhat.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/cpu/mtrr/main.c

@@ -615,40 +615,21 @@ static int __init mtrr_init(void)
 		size_or_mask = 0xff000000;	/* 36 bits */
 		size_and_mask = 0x00f00000;
 
-		switch (boot_cpu_data.x86_vendor) {
-		case X86_VENDOR_AMD:
-			/* The original Athlon docs said that
-			   total addressable memory is 44 bits wide.
-			   It was not really clear whether its MTRRs
-			   follow this or not. (Read: 44 or 36 bits).
-			   However, "x86-64_overview.pdf" explicitly
-			   states that "previous implementations support
-			   36 bit MTRRs" and also provides a way to
-			   query the width (in bits) of the physical
-			   addressable memory on the Hammer family.
-			 */
-			if (boot_cpu_data.x86 == 15
-			    && (cpuid_eax(0x80000000) >= 0x80000008)) {
+		/* This is an AMD specific MSR, but we assume(hope?) that
+		   Intel will implement it to when they extend the address
+		   bus of the Xeon. */
+		if (cpuid_eax(0x80000000) >= 0x80000008) {
 			u32 phys_addr;
 			phys_addr = cpuid_eax(0x80000008) & 0xff;
-				size_or_mask =
-				    ~((1 << (phys_addr - PAGE_SHIFT)) - 1);
+			size_or_mask = ~((1 << (phys_addr - PAGE_SHIFT)) - 1);
 			size_and_mask = ~size_or_mask & 0xfff00000;
-			}
-			/* Athlon MTRRs use an Intel-compatible interface for 
-			 * getting and setting */
-			break;
-		case X86_VENDOR_CENTAUR:
-			if (boot_cpu_data.x86 == 6) {
-				/* VIA Cyrix family have Intel style MTRRs, but don't support PAE */
+		} else if (boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR &&
+			   boot_cpu_data.x86 == 6) {
+			/* VIA C* family have Intel style MTRRs, but
+			   don't support PAE */
 			size_or_mask = 0xfff00000;	/* 32 bits */
 			size_and_mask = 0;
 		}
-			break;
-		
-		default:
-			break;
-		}
 	} else {
 		switch (boot_cpu_data.x86_vendor) {
 		case X86_VENDOR_AMD: