[PATCH] x86_64: Force correct address space size for MTRR on some 64bit Intel Xeons

They report 40bit, but only have 36bits of physical address space.
This caused problems with setting up the correct masks for MTRR.

CPUID workaround for steppings 0F33h(supporting x86) and 0F34h(supporting x86
and EM64T). Detail info can be found at:
http://download.intel.com/design/Xeon/specupdt/30240216.pdf
http://download.intel.com/design/Pentium4/specupdt/30235221.pdf

Signed-off-by: Shaohua Li<shaohua.li@intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index 2ad3556dda52..476ee034fca2 100644
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -995,6 +995,11 @@ static void __cpuinit init_intel(struct cpuinfo_x86 *c)
                 unsigned eax = cpuid_eax(0x80000008);
                 c->x86_virt_bits = (eax >> 8) & 0xff;
                 c->x86_phys_bits = eax & 0xff;
+                /* CPUID workaround for Intel 0F34 CPU */
+                if (c->x86_vendor == X86_VENDOR_INTEL &&
+                    c->x86 == 0xF && c->x86_model == 0x3 &&
+                    c->x86_mask == 0x4)
+                        c->x86_phys_bits = 36;
         }
 
         if (c->x86 == 15)