hw/alpha: Don't machine check on missing pci i/o

Not really correct, but we don't implement all of the random devices
that the kernel looks for.  This is good enough to keep us booting.

Signed-off-by: Richard Henderson <rth@twiddle.net>

hw/alpha/alpha_sys.h

@@ -14,6 +14,7 @@ PCIBus *typhoon_init(ram_addr_t, ISABus **, qemu_irq *, AlphaCPU *[4],
                      pci_map_irq_fn);
 
 /* alpha_pci.c.  */
+extern const MemoryRegionOps alpha_pci_ignore_ops;
 extern const MemoryRegionOps alpha_pci_conf1_ops;
 extern const MemoryRegionOps alpha_pci_iack_ops;
 

hw/alpha/pci.c

@@ -12,6 +12,32 @@
 #include "sysemu/sysemu.h"
 
 
+/* Fallback for unassigned PCI I/O operations.  Avoids MCHK.  */
+
+static uint64_t ignore_read(void *opaque, hwaddr addr, unsigned size)
+{
+    return 0;
+}
+
+static void ignore_write(void *opaque, hwaddr addr, uint64_t v, unsigned size)
+{
+}
+
+const MemoryRegionOps alpha_pci_ignore_ops = {
+    .read = ignore_read,
+    .write = ignore_write,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+    .valid = {
+        .min_access_size = 1,
+        .max_access_size = 8,
+    },
+    .impl = {
+        .min_access_size = 1,
+        .max_access_size = 8,
+    },
+};
+
+
 /* PCI config space reads/writes, to byte-word addressable memory.  */
 static uint64_t bw_conf1_read(void *opaque, hwaddr addr,
                               unsigned size)

hw/alpha/typhoon.c

@@ -764,7 +764,8 @@ PCIBus *typhoon_init(ram_addr_t ram_size, ISABus **isa_bus,
                                 &s->pchip.reg_mem);
 
     /* Pchip0 PCI I/O, 0x801.FC00.0000, 32MB.  */
-    memory_region_init(&s->pchip.reg_io, OBJECT(s), "pci0-io", 32*MB);
+    memory_region_init_io(&s->pchip.reg_io, OBJECT(s), &alpha_pci_ignore_ops,
+                          NULL, "pci0-io", 32*MB);
     memory_region_add_subregion(addr_space, 0x801fc000000ULL,
                                 &s->pchip.reg_io);