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/include/asm/mach-generic/spaces.h

@@ -20,14 +20,21 @@
 #endif
 
 #ifdef CONFIG_32BIT
-
+#ifdef CONFIG_KVM_GUEST
+#define CAC_BASE		_AC(0x40000000, UL)
+#else
 #define CAC_BASE		_AC(0x80000000, UL)
+#endif
 #define IO_BASE			_AC(0xa0000000, UL)
 #define UNCAC_BASE		_AC(0xa0000000, UL)
 
 #ifndef MAP_BASE
+#ifdef CONFIG_KVM_GUEST
+#define MAP_BASE		_AC(0x60000000, UL)
+#else
 #define MAP_BASE		_AC(0xc0000000, UL)
 #endif
+#endif
 
 /*
  * Memory above this physical address will be considered highmem.

arch/mips/include/asm/processor.h

@@ -44,11 +44,16 @@ extern unsigned int vced_count, vcei_count;
 #define SPECIAL_PAGES_SIZE PAGE_SIZE
 
 #ifdef CONFIG_32BIT
+#ifdef CONFIG_KVM_GUEST
+/* User space process size is limited to 1GB in KVM Guest Mode */
+#define TASK_SIZE	0x3fff8000UL
+#else
 /*
  * User space process size: 2GB. This is hardcoded into a few places,
  * so don't change it unless you know what you are doing.
  */
 #define TASK_SIZE	0x7fff8000UL
+#endif
 
 #ifdef __KERNEL__
 #define STACK_TOP_MAX	TASK_SIZE

arch/mips/include/asm/uaccess.h

@@ -23,7 +23,11 @@
  */
 #ifdef CONFIG_32BIT
 
-#define __UA_LIMIT	0x80000000UL
+#ifdef CONFIG_KVM_GUEST
+#define __UA_LIMIT 0x40000000UL
+#else
+#define __UA_LIMIT 0x80000000UL
+#endif
 
 #define __UA_ADDR	".word"
 #define __UA_LA		"la"
@@ -55,8 +59,13 @@ extern u64 __ua_limit;
  * address in this range it's the process's problem, not ours :-)
  */
 
+#ifdef CONFIG_KVM_GUEST
+#define KERNEL_DS	((mm_segment_t) { 0x80000000UL })
+#define USER_DS		((mm_segment_t) { 0xC0000000UL })
+#else
 #define KERNEL_DS	((mm_segment_t) { 0UL })
 #define USER_DS		((mm_segment_t) { __UA_LIMIT })
+#endif
 
 #define VERIFY_READ    0
 #define VERIFY_WRITE   1

arch/mips/kernel/binfmt_elfo32.c

@@ -48,7 +48,11 @@ typedef elf_fpreg_t elf_fpregset_t[ELF_NFPREG];
 	__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)
 

arch/mips/kernel/cevt-r4k.c

@@ -118,6 +118,10 @@ int c0_compare_int_usable(void)
 	unsigned int delta;
 	unsigned int cnt;
 
+#ifdef CONFIG_KVM_GUEST
+    return 1;
+#endif
+
 	/*
 	 * IP7 already pending?	 Try to clear it by acking the timer.
 	 */

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);
 	}

arch/mips/mti-malta/malta-time.c

@@ -76,6 +76,21 @@ static void __init estimate_frequencies(void)
 	unsigned int count, start;
 	unsigned int giccount = 0, gicstart = 0;
 
+#if defined (CONFIG_KVM_GUEST) && defined (CONFIG_KVM_HOST_FREQ)
+	unsigned int prid = read_c0_prid() & 0xffff00;
+
+	/*
+	 * XXXKYMA: hardwire the CPU frequency to Host Freq/4
+	 */
+	count = (CONFIG_KVM_HOST_FREQ * 1000000) >> 3;
+	if ((prid != (PRID_COMP_MIPS | PRID_IMP_20KC)) &&
+	    (prid != (PRID_COMP_MIPS | PRID_IMP_25KF)))
+		count *= 2;
+
+	mips_hpt_frequency = count;
+	return;
+#endif
+
 	local_irq_save(flags);
 
 	/* Start counter exactly on falling edge of update flag. */