hw/ide: Fix crash when plugging a piix3-ide device into the x-remote machine

QEMU currently crashes when the user tries to do something like:

 qemu-system-x86_64 -M x-remote -device piix3-ide

This happens because the "isabus" variable is not initialized with
the x-remote machine yet. Add a proper check for this condition
and propagate the error to the caller, so we can fail there gracefully.

Message-Id: <20210416125256.2039734-1-thuth@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

hw/ide/ioport.c

@@ -50,15 +50,19 @@ static const MemoryRegionPortio ide_portio2_list[] = {
     PORTIO_END_OF_LIST(),
 };
 
-void ide_init_ioport(IDEBus *bus, ISADevice *dev, int iobase, int iobase2)
+int ide_init_ioport(IDEBus *bus, ISADevice *dev, int iobase, int iobase2)
 {
+    int ret;
+
     /* ??? Assume only ISA and PCI configurations, and that the PCI-ISA
        bridge has been setup properly to always register with ISA.  */
-    isa_register_portio_list(dev, &bus->portio_list,
+    ret = isa_register_portio_list(dev, &bus->portio_list,
-                             iobase, ide_portio_list, bus, "ide");
+                                   iobase, ide_portio_list, bus, "ide");
 
-    if (iobase2) {
+    if (ret == 0 && iobase2) {
-        isa_register_portio_list(dev, &bus->portio2_list,
+        ret = isa_register_portio_list(dev, &bus->portio2_list,
-                                 iobase2, ide_portio2_list, bus, "ide");
+                                       iobase2, ide_portio2_list, bus, "ide");
     }
+
+    return ret;
 }

hw/ide/piix.c

@@ -26,6 +26,7 @@
 #include "qemu/osdep.h"
 #include "hw/pci/pci.h"
 #include "migration/vmstate.h"
+#include "qapi/error.h"
 #include "qemu/module.h"
 #include "sysemu/block-backend.h"
 #include "sysemu/blockdev.h"
@@ -123,7 +124,8 @@ static void piix_ide_reset(DeviceState *dev)
     pci_conf[0x20] = 0x01; /* BMIBA: 20-23h */
 }
 
-static void pci_piix_init_ports(PCIIDEState *d) {
+static int pci_piix_init_ports(PCIIDEState *d)
+{
     static const struct {
         int iobase;
         int iobase2;
@@ -132,24 +134,30 @@ static void pci_piix_init_ports(PCIIDEState *d) {
         {0x1f0, 0x3f6, 14},
         {0x170, 0x376, 15},
     };
-    int i;
+    int i, ret;
 
     for (i = 0; i < 2; i++) {
         ide_bus_new(&d->bus[i], sizeof(d->bus[i]), DEVICE(d), i, 2);
-        ide_init_ioport(&d->bus[i], NULL, port_info[i].iobase,
+        ret = ide_init_ioport(&d->bus[i], NULL, port_info[i].iobase,
-                        port_info[i].iobase2);
+                              port_info[i].iobase2);
+        if (ret) {
+            return ret;
+        }
         ide_init2(&d->bus[i], isa_get_irq(NULL, port_info[i].isairq));
 
         bmdma_init(&d->bus[i], &d->bmdma[i], d);
         d->bmdma[i].bus = &d->bus[i];
         ide_register_restart_cb(&d->bus[i]);
     }
+
+    return 0;
 }
 
 static void pci_piix_ide_realize(PCIDevice *dev, Error **errp)
 {
     PCIIDEState *d = PCI_IDE(dev);
     uint8_t *pci_conf = dev->config;
+    int rc;
 
     pci_conf[PCI_CLASS_PROG] = 0x80; // legacy ATA mode
 
@@ -158,7 +166,11 @@ static void pci_piix_ide_realize(PCIDevice *dev, Error **errp)
 
     vmstate_register(VMSTATE_IF(dev), 0, &vmstate_ide_pci, d);
 
-    pci_piix_init_ports(d);
+    rc = pci_piix_init_ports(d);
+    if (rc) {
+        error_setg_errno(errp, -rc, "Failed to realize %s",
+                         object_get_typename(OBJECT(dev)));
+    }
 }
 
 int pci_piix3_xen_ide_unplug(DeviceState *dev, bool aux)

hw/isa/isa-bus.c

@@ -131,13 +131,17 @@ void isa_register_ioport(ISADevice *dev, MemoryRegion *io, uint16_t start)
     isa_init_ioport(dev, start);
 }
 
-void isa_register_portio_list(ISADevice *dev,
+int isa_register_portio_list(ISADevice *dev,
-                              PortioList *piolist, uint16_t start,
+                             PortioList *piolist, uint16_t start,
-                              const MemoryRegionPortio *pio_start,
+                             const MemoryRegionPortio *pio_start,
-                              void *opaque, const char *name)
+                             void *opaque, const char *name)
 {
     assert(piolist && !piolist->owner);
 
+    if (!isabus) {
+        return -ENODEV;
+    }
+
     /* START is how we should treat DEV, regardless of the actual
        contents of the portio array.  This is how the old code
        actually handled e.g. the FDC device.  */
@@ -145,6 +149,8 @@ void isa_register_portio_list(ISADevice *dev,
 
     portio_list_init(piolist, OBJECT(dev), pio_start, opaque, name);
     portio_list_add(piolist, isabus->address_space_io, start);
+
+    return 0;
 }
 
 static void isa_device_init(Object *obj)

include/hw/ide/internal.h

@@ -624,7 +624,7 @@ int ide_init_drive(IDEState *s, BlockBackend *blk, IDEDriveKind kind,
                    int chs_trans, Error **errp);
 void ide_init2(IDEBus *bus, qemu_irq irq);
 void ide_exit(IDEState *s);
-void ide_init_ioport(IDEBus *bus, ISADevice *isa, int iobase, int iobase2);
+int ide_init_ioport(IDEBus *bus, ISADevice *isa, int iobase, int iobase2);
 void ide_register_restart_cb(IDEBus *bus);
 
 void ide_exec_cmd(IDEBus *bus, uint32_t val);

include/hw/isa/isa.h

@@ -132,12 +132,15 @@ void isa_register_ioport(ISADevice *dev, MemoryRegion *io, uint16_t start);
  * @portio: the ports, sorted by offset.
  * @opaque: passed into the portio callbacks.
  * @name: passed into memory_region_init_io.
+ *
+ * Returns: 0 on success, negative error code otherwise (e.g. if the
+ *          ISA bus is not available)
  */
-void isa_register_portio_list(ISADevice *dev,
+int isa_register_portio_list(ISADevice *dev,
-                              PortioList *piolist,
+                             PortioList *piolist,
-                              uint16_t start,
+                             uint16_t start,
-                              const MemoryRegionPortio *portio,
+                             const MemoryRegionPortio *portio,
-                              void *opaque, const char *name);
+                             void *opaque, const char *name);
 
 static inline ISABus *isa_bus_from_device(ISADevice *d)
 {