KVM/MIPS32: KVM Guest kernel support.

Both Guest kernel and Guest Userspace execute in UM. The memory map is as follows:
Guest User address space:   0x00000000 -> 0x40000000
Guest Kernel Unmapped:      0x40000000 -> 0x60000000
Guest Kernel Mapped:        0x60000000 -> 0x80000000
- Guest Usermode virtual memory is limited to 1GB.

Signed-off-by: Sanjay Lal <sanjayl@kymasys.com>
Cc: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/traps.c

@@ -1713,7 +1713,12 @@ void __init trap_init(void)
 		ebase = (unsigned long)
 			__alloc_bootmem(size, 1 << fls(size), 0);
 	} else {
-		ebase = CKSEG0;
+#ifdef CONFIG_KVM_GUEST
+#define KVM_GUEST_KSEG0     0x40000000
+        ebase = KVM_GUEST_KSEG0;
+#else
+        ebase = CKSEG0;
+#endif
 		if (cpu_has_mips_r2)
 			ebase += (read_c0_ebase() & 0x3ffff000);
 	}