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qemu/include/hw/scsi/scsi.h
Markus Armbruster b69c3c21a5 qdev: Unrealize must not fail 
Devices may have component devices and buses.

Device realization may fail.  Realization is recursive: a device's
realize() method realizes its components, and device_set_realized()
realizes its buses (which should in turn realize the devices on that
bus, except bus_set_realized() doesn't implement that, yet).

When realization of a component or bus fails, we need to roll back:
unrealize everything we realized so far.  If any of these unrealizes
failed, the device would be left in an inconsistent state.  Must not
happen.

device_set_realized() lets it happen: it ignores errors in the roll
back code starting at label child_realize_fail.

Since realization is recursive, unrealization must be recursive, too.
But how could a partly failed unrealize be rolled back?  We'd have to
re-realize, which can fail.  This design is fundamentally broken.

device_set_realized() does not roll back at all.  Instead, it keeps
unrealizing, ignoring further errors.

It can screw up even for a device with no buses: if the lone
dc->unrealize() fails, it still unregisters vmstate, and calls
listeners' unrealize() callback.

bus_set_realized() does not roll back either.  Instead, it stops
unrealizing.

Fortunately, no unrealize method can fail, as we'll see below.

To fix the design error, drop parameter @errp from all the unrealize
methods.

Any unrealize method that uses @errp now needs an update.  This leads
us to unrealize() methods that can fail.  Merely passing it to another
unrealize method cannot cause failure, though.  Here are the ones that
do other things with @errp:

* virtio_serial_device_unrealize()

  Fails when qbus_set_hotplug_handler() fails, but still does all the
  other work.  On failure, the device would stay realized with its
  resources completely gone.  Oops.  Can't happen, because
  qbus_set_hotplug_handler() can't actually fail here.  Pass
  &error_abort to qbus_set_hotplug_handler() instead.

* hw/ppc/spapr_drc.c's unrealize()

  Fails when object_property_del() fails, but all the other work is
  already done.  On failure, the device would stay realized with its
  vmstate registration gone.  Oops.  Can't happen, because
  object_property_del() can't actually fail here.  Pass &error_abort
  to object_property_del() instead.

* spapr_phb_unrealize()

  Fails and bails out when remove_drcs() fails, but other work is
  already done.  On failure, the device would stay realized with some
  of its resources gone.  Oops.  remove_drcs() fails only when
  chassis_from_bus()'s object_property_get_uint() fails, and it can't
  here.  Pass &error_abort to remove_drcs() instead.

Therefore, no unrealize method can fail before this patch.

device_set_realized()'s recursive unrealization via bus uses
object_property_set_bool().  Can't drop @errp there, so pass
&error_abort.

We similarly unrealize with object_property_set_bool() elsewhere,
always ignoring errors.  Pass &error_abort instead.

Several unrealize methods no longer handle errors from other unrealize
methods: virtio_9p_device_unrealize(),
virtio_input_device_unrealize(), scsi_qdev_unrealize(), ...
Much of the deleted error handling looks wrong anyway.

One unrealize methods no longer ignore such errors:
usb_ehci_pci_exit().

Several realize methods no longer ignore errors when rolling back:
v9fs_device_realize_common(), pci_qdev_unrealize(),
spapr_phb_realize(), usb_qdev_realize(), vfio_ccw_realize(),
virtio_device_realize().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20200505152926.18877-17-armbru@redhat.com>
2020-05-15 07:08:14 +02:00

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#ifndef QEMU_HW_SCSI_H
#define QEMU_HW_SCSI_H
#include "block/aio.h"
#include "hw/block/block.h"
#include "hw/qdev-core.h"
#include "scsi/utils.h"
#include "qemu/notify.h"
#define MAX_SCSI_DEVS 255
typedef struct SCSIBus SCSIBus;
typedef struct SCSIBusInfo SCSIBusInfo;
typedef struct SCSIDevice SCSIDevice;
typedef struct SCSIRequest SCSIRequest;
typedef struct SCSIReqOps SCSIReqOps;
#define SCSI_SENSE_BUF_SIZE_OLD 96
#define SCSI_SENSE_BUF_SIZE 252
struct SCSIRequest {
SCSIBus *bus;
SCSIDevice *dev;
const SCSIReqOps *ops;
uint32_t refcount;
uint32_t tag;
uint32_t lun;
uint32_t status;
void *hba_private;
size_t resid;
SCSICommand cmd;
NotifierList cancel_notifiers;
/* Note:
* - fields before sense are initialized by scsi_req_alloc;
* - sense[] is uninitialized;
* - fields after sense are memset to 0 by scsi_req_alloc.
* */
uint8_t sense[SCSI_SENSE_BUF_SIZE];
uint32_t sense_len;
bool enqueued;
bool io_canceled;
bool retry;
bool dma_started;
BlockAIOCB *aiocb;
QEMUSGList *sg;
QTAILQ_ENTRY(SCSIRequest) next;
};
#define TYPE_SCSI_DEVICE "scsi-device"
#define SCSI_DEVICE(obj) \
OBJECT_CHECK(SCSIDevice, (obj), TYPE_SCSI_DEVICE)
#define SCSI_DEVICE_CLASS(klass) \
OBJECT_CLASS_CHECK(SCSIDeviceClass, (klass), TYPE_SCSI_DEVICE)
#define SCSI_DEVICE_GET_CLASS(obj) \
OBJECT_GET_CLASS(SCSIDeviceClass, (obj), TYPE_SCSI_DEVICE)
typedef struct SCSIDeviceClass {
DeviceClass parent_class;
void (*realize)(SCSIDevice *dev, Error **errp);
void (*unrealize)(SCSIDevice *dev);
int (*parse_cdb)(SCSIDevice *dev, SCSICommand *cmd, uint8_t *buf,
void *hba_private);
SCSIRequest *(*alloc_req)(SCSIDevice *s, uint32_t tag, uint32_t lun,
uint8_t *buf, void *hba_private);
void (*unit_attention_reported)(SCSIDevice *s);
} SCSIDeviceClass;
struct SCSIDevice
{
DeviceState qdev;
VMChangeStateEntry *vmsentry;
QEMUBH *bh;
uint32_t id;
BlockConf conf;
SCSISense unit_attention;
bool sense_is_ua;
uint8_t sense[SCSI_SENSE_BUF_SIZE];
uint32_t sense_len;
QTAILQ_HEAD(, SCSIRequest) requests;
uint32_t channel;
uint32_t lun;
int blocksize;
int type;
uint64_t max_lba;
uint64_t wwn;
uint64_t port_wwn;
int scsi_version;
int default_scsi_version;
bool needs_vpd_bl_emulation;
bool hba_supports_iothread;
};
extern const VMStateDescription vmstate_scsi_device;
#define VMSTATE_SCSI_DEVICE(_field, _state) { \
.name = (stringify(_field)), \
.size = sizeof(SCSIDevice), \
.vmsd = &vmstate_scsi_device, \
.flags = VMS_STRUCT, \
.offset = vmstate_offset_value(_state, _field, SCSIDevice), \
}
/* cdrom.c */
int cdrom_read_toc(int nb_sectors, uint8_t *buf, int msf, int start_track);
int cdrom_read_toc_raw(int nb_sectors, uint8_t *buf, int msf, int session_num);
/* scsi-bus.c */
struct SCSIReqOps {
size_t size;
void (*free_req)(SCSIRequest *req);
int32_t (*send_command)(SCSIRequest *req, uint8_t *buf);
void (*read_data)(SCSIRequest *req);
void (*write_data)(SCSIRequest *req);
uint8_t *(*get_buf)(SCSIRequest *req);
void (*save_request)(QEMUFile *f, SCSIRequest *req);
void (*load_request)(QEMUFile *f, SCSIRequest *req);
};
struct SCSIBusInfo {
int tcq;
int max_channel, max_target, max_lun;
int (*parse_cdb)(SCSIDevice *dev, SCSICommand *cmd, uint8_t *buf,
void *hba_private);
void (*transfer_data)(SCSIRequest *req, uint32_t arg);
void (*complete)(SCSIRequest *req, uint32_t arg, size_t resid);
void (*cancel)(SCSIRequest *req);
void (*change)(SCSIBus *bus, SCSIDevice *dev, SCSISense sense);
QEMUSGList *(*get_sg_list)(SCSIRequest *req);
void (*save_request)(QEMUFile *f, SCSIRequest *req);
void *(*load_request)(QEMUFile *f, SCSIRequest *req);
void (*free_request)(SCSIBus *bus, void *priv);
};
#define TYPE_SCSI_BUS "SCSI"
#define SCSI_BUS(obj) OBJECT_CHECK(SCSIBus, (obj), TYPE_SCSI_BUS)
struct SCSIBus {
BusState qbus;
int busnr;
SCSISense unit_attention;
const SCSIBusInfo *info;
};
void scsi_bus_new(SCSIBus *bus, size_t bus_size, DeviceState *host,
const SCSIBusInfo *info, const char *bus_name);
static inline SCSIBus *scsi_bus_from_device(SCSIDevice *d)
{
return DO_UPCAST(SCSIBus, qbus, d->qdev.parent_bus);
}
SCSIDevice *scsi_bus_legacy_add_drive(SCSIBus *bus, BlockBackend *blk,
int unit, bool removable, int bootindex,
bool share_rw,
BlockdevOnError rerror,
BlockdevOnError werror,
const char *serial, Error **errp);
void scsi_bus_legacy_handle_cmdline(SCSIBus *bus);
void scsi_legacy_handle_cmdline(void);
SCSIRequest *scsi_req_alloc(const SCSIReqOps *reqops, SCSIDevice *d,
uint32_t tag, uint32_t lun, void *hba_private);
SCSIRequest *scsi_req_new(SCSIDevice *d, uint32_t tag, uint32_t lun,
uint8_t *buf, void *hba_private);
int32_t scsi_req_enqueue(SCSIRequest *req);
SCSIRequest *scsi_req_ref(SCSIRequest *req);
void scsi_req_unref(SCSIRequest *req);
int scsi_bus_parse_cdb(SCSIDevice *dev, SCSICommand *cmd, uint8_t *buf,
void *hba_private);
int scsi_req_parse_cdb(SCSIDevice *dev, SCSICommand *cmd, uint8_t *buf);
void scsi_req_build_sense(SCSIRequest *req, SCSISense sense);
void scsi_req_print(SCSIRequest *req);
void scsi_req_continue(SCSIRequest *req);
void scsi_req_data(SCSIRequest *req, int len);
void scsi_req_complete(SCSIRequest *req, int status);
uint8_t *scsi_req_get_buf(SCSIRequest *req);
int scsi_req_get_sense(SCSIRequest *req, uint8_t *buf, int len);
void scsi_req_cancel_complete(SCSIRequest *req);
void scsi_req_cancel(SCSIRequest *req);
void scsi_req_cancel_async(SCSIRequest *req, Notifier *notifier);
void scsi_req_retry(SCSIRequest *req);
void scsi_device_purge_requests(SCSIDevice *sdev, SCSISense sense);
void scsi_device_set_ua(SCSIDevice *sdev, SCSISense sense);
void scsi_device_report_change(SCSIDevice *dev, SCSISense sense);
void scsi_device_unit_attention_reported(SCSIDevice *dev);
void scsi_generic_read_device_inquiry(SCSIDevice *dev);
int scsi_device_get_sense(SCSIDevice *dev, uint8_t *buf, int len, bool fixed);
int scsi_SG_IO_FROM_DEV(BlockBackend *blk, uint8_t *cmd, uint8_t cmd_size,
uint8_t *buf, uint8_t buf_size);
SCSIDevice *scsi_device_find(SCSIBus *bus, int channel, int target, int lun);
/* scsi-generic.c. */
extern const SCSIReqOps scsi_generic_req_ops;
#endif
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