exec: eliminate io_mem_ram

It is never used, the IOTLB always goes through io_mem_notdirty.

In fact in softmmu_template.h, if it were, QEMU would crash just
below the tests, as soon as io_mem_read/write dispatches to
error_mem_read/write.
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

exec.c

@@ -66,7 +66,7 @@ AddressSpace address_space_io;
 AddressSpace address_space_memory;
 DMAContext dma_context_memory;
 
-MemoryRegion io_mem_ram, io_mem_rom, io_mem_unassigned, io_mem_notdirty;
+MemoryRegion io_mem_rom, io_mem_unassigned, io_mem_notdirty;
 static MemoryRegion io_mem_subpage_ram;
 
 #endif
@@ -200,8 +200,7 @@ MemoryRegionSection *phys_page_find(AddressSpaceDispatch *d, hwaddr index)
 
 bool memory_region_is_unassigned(MemoryRegion *mr)
 {
-    return mr != &io_mem_ram && mr != &io_mem_rom
-        && mr != &io_mem_notdirty && !mr->rom_device
+    return mr != &io_mem_rom && mr != &io_mem_notdirty && !mr->rom_device
         && mr != &io_mem_watch;
 }
 #endif
@@ -1419,18 +1418,6 @@ static uint64_t error_mem_read(void *opaque, hwaddr addr,
     abort();
 }
 
-static void error_mem_write(void *opaque, hwaddr addr,
-                            uint64_t value, unsigned size)
-{
-    abort();
-}
-
-static const MemoryRegionOps error_mem_ops = {
-    .read = error_mem_read,
-    .write = error_mem_write,
-    .endianness = DEVICE_NATIVE_ENDIAN,
-};
-
 static const MemoryRegionOps rom_mem_ops = {
     .read = error_mem_read,
     .write = unassigned_mem_write,
@@ -1691,7 +1678,6 @@ MemoryRegion *iotlb_to_region(hwaddr index)
 
 static void io_mem_init(void)
 {
-    memory_region_init_io(&io_mem_ram, &error_mem_ops, NULL, "ram", UINT64_MAX);
     memory_region_init_io(&io_mem_rom, &rom_mem_ops, NULL, "rom", UINT64_MAX);
     memory_region_init_io(&io_mem_unassigned, &unassigned_mem_ops, NULL,
                           "unassigned", UINT64_MAX);

include/exec/cpu-common.h

@@ -110,7 +110,6 @@ void stq_phys(hwaddr addr, uint64_t val);
 void cpu_physical_memory_write_rom(hwaddr addr,
                                    const uint8_t *buf, int len);
 
-extern struct MemoryRegion io_mem_ram;
 extern struct MemoryRegion io_mem_rom;
 extern struct MemoryRegion io_mem_unassigned;
 extern struct MemoryRegion io_mem_notdirty;

include/exec/softmmu_template.h

@@ -68,7 +68,7 @@ static inline DATA_TYPE glue(io_read, SUFFIX)(CPUArchState *env,
 
     physaddr = (physaddr & TARGET_PAGE_MASK) + addr;
     env->mem_io_pc = retaddr;
-    if (mr != &io_mem_ram && mr != &io_mem_rom
+    if (mr != &io_mem_rom
         && mr != &io_mem_unassigned
         && mr != &io_mem_notdirty
             && !can_do_io(env)) {
@@ -218,7 +218,7 @@ static inline void glue(io_write, SUFFIX)(CPUArchState *env,
     MemoryRegion *mr = iotlb_to_region(physaddr);
 
     physaddr = (physaddr & TARGET_PAGE_MASK) + addr;
-    if (mr != &io_mem_ram && mr != &io_mem_rom
+    if (mr != &io_mem_rom
         && mr != &io_mem_unassigned
         && mr != &io_mem_notdirty
             && !can_do_io(env)) {