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>
diff --git a/arch/mips/kernel/binfmt_elfo32.c b/arch/mips/kernel/binfmt_elfo32.c
index 556a435..97c5a16 100644
--- a/arch/mips/kernel/binfmt_elfo32.c
+++ b/arch/mips/kernel/binfmt_elfo32.c
@@ -48,7 +48,11 @@
 	__res;								\
 })
 
+#ifdef CONFIG_KVM_GUEST
+#define TASK32_SIZE		0x3fff8000UL
+#else
 #define TASK32_SIZE		0x7fff8000UL
+#endif
 #undef ELF_ET_DYN_BASE
 #define ELF_ET_DYN_BASE		(TASK32_SIZE / 3 * 2)
 
diff --git a/arch/mips/kernel/cevt-r4k.c b/arch/mips/kernel/cevt-r4k.c
index 07b847d..fd75d71 100644
--- a/arch/mips/kernel/cevt-r4k.c
+++ b/arch/mips/kernel/cevt-r4k.c
@@ -118,6 +118,10 @@
 	unsigned int delta;
 	unsigned int cnt;
 
+#ifdef CONFIG_KVM_GUEST
+    return 1;
+#endif
+
 	/*
 	 * IP7 already pending?	 Try to clear it by acking the timer.
 	 */
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index a200b5b..59351e5 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -1713,7 +1713,12 @@
 		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);
 	}