target-sh4: implement writes to mmaped ITLB

Some Linux kernels seems to implement ITLB/UTLB flushing through by
writing all TLB entries through the memory mapped interface instead
of writing one to MMUCR.TI.

Implement memory mapped ITLB write interface so that such kernels can
boot. This fixes https://bugs.launchpad.net/bugs/700774 .
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>

hw/sh7750.c

@@ -670,6 +670,8 @@ static void sh7750_mmct_writel(void *opaque, target_phys_addr_t addr,
         /* do nothing */
 	break;
     case MM_ITLB_ADDR:
+        cpu_sh4_write_mmaped_itlb_addr(s->cpu, addr, mem_value);
+        break;
     case MM_ITLB_DATA:
         /* XXXXX */
         abort();

target-sh4/cpu.h

@@ -172,6 +172,8 @@ void do_interrupt(CPUSH4State * env);
 void sh4_cpu_list(FILE *f, fprintf_function cpu_fprintf);
 #if !defined(CONFIG_USER_ONLY)
 void cpu_sh4_invalidate_tlb(CPUSH4State *s);
+void cpu_sh4_write_mmaped_itlb_addr(CPUSH4State *s, target_phys_addr_t addr,
+				    uint32_t mem_value);
 void cpu_sh4_write_mmaped_utlb_addr(CPUSH4State *s, target_phys_addr_t addr,
 				    uint32_t mem_value);
 #endif

target-sh4/helper.c

@@ -544,6 +544,25 @@ void cpu_load_tlb(CPUSH4State * env)
     tlb_flush(s, 1);
 }
 
+void cpu_sh4_write_mmaped_itlb_addr(CPUSH4State *s, target_phys_addr_t addr,
+				    uint32_t mem_value)
+{
+    uint32_t vpn = (mem_value & 0xfffffc00) >> 10;
+    uint8_t v = (uint8_t)((mem_value & 0x00000100) >> 8);
+    uint8_t asid = (uint8_t)(mem_value & 0x000000ff);
+
+    int index = (addr & 0x00003f00) >> 8;
+    tlb_t * entry = &s->itlb[index];
+    if (entry->v) {
+        /* Overwriting valid entry in itlb. */
+        target_ulong address = entry->vpn << 10;
+        tlb_flush_page(s, address);
+    }
+    entry->asid = asid;
+    entry->vpn = vpn;
+    entry->v = v;
+}
+
 void cpu_sh4_write_mmaped_utlb_addr(CPUSH4State *s, target_phys_addr_t addr,
 				    uint32_t mem_value)
 {