Add a vmstate subsection to SCSIDiskState so that scsi-block devices can transfer their reservation state during live migration. Upon loading the subsection, the destination QEMU invokes the PERSISTENT RESERVE OUT command's PREEMPT service action to atomically move the reservation from the source I_T nexus to the destination I_T nexus. This results in transparent live migration of SCSI reservations.
This approach is incomplete since SCSI reservations are cooperative and other hosts could interfere. Neither the source QEMU nor the destination QEMU are aware of changes made by other hosts. The assumption is that reservation is not taken over by a third host without cooperation from the source host. I considered adding the vmstate subsection to SCSIDevice instead of SCSIDiskState, since reservations are part of the SCSI Primary Commands that other devices apart from disks could support. However, due to fragility of migrating reservations, we will probably limit support to scsi-block and maybe scsi-disk in the future. In the end, I think it makes sense to place this within scsi-disk.c. Signed-off-by: Stefan Hajnoczi <[email protected]> --- include/hw/scsi/scsi.h | 1 + hw/core/machine.c | 4 +- hw/scsi/scsi-disk.c | 49 ++++++++++++++++++++++++- hw/scsi/scsi-generic.c | 83 ++++++++++++++++++++++++++++++++++++++++++ hw/scsi/trace-events | 1 + 5 files changed, 136 insertions(+), 2 deletions(-) diff --git a/include/hw/scsi/scsi.h b/include/hw/scsi/scsi.h index c5ec58089b..d104557bac 100644 --- a/include/hw/scsi/scsi.h +++ b/include/hw/scsi/scsi.h @@ -253,6 +253,7 @@ SCSIDevice *scsi_device_get(SCSIBus *bus, int channel, int target, int lun); /* scsi-generic.c. */ extern const SCSIReqOps scsi_generic_req_ops; +bool scsi_generic_pr_state_post_load_errp(SCSIDevice *s, Error **errp); /* scsi-disk.c */ #define SCSI_DISK_QUIRK_MODE_PAGE_APPLE_VENDOR 0 diff --git a/hw/core/machine.c b/hw/core/machine.c index 6411e68856..16134f8ce5 100644 --- a/hw/core/machine.c +++ b/hw/core/machine.c @@ -38,7 +38,9 @@ #include "hw/acpi/generic_event_device.h" #include "qemu/audio.h" -GlobalProperty hw_compat_10_2[] = {}; +GlobalProperty hw_compat_10_2[] = { + { "scsi-block", "migrate-pr", "off" }, +}; const size_t hw_compat_10_2_len = G_N_ELEMENTS(hw_compat_10_2); GlobalProperty hw_compat_10_1[] = { diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c index 76fe5f085b..82e5b59534 100644 --- a/hw/scsi/scsi-disk.c +++ b/hw/scsi/scsi-disk.c @@ -3209,6 +3209,46 @@ static const Property scsi_hd_properties[] = { DEFINE_BLOCK_CHS_PROPERTIES(SCSIDiskState, qdev.conf), }; +#ifdef __linux__ +static bool scsi_disk_pr_state_post_load_errp(void *opaque, int version_id, Error **errp) +{ + SCSIDiskState *s = opaque; + SCSIDevice *dev = &s->qdev; + + return scsi_generic_pr_state_post_load_errp(dev, errp); +} + +static bool scsi_disk_pr_state_needed(void *opaque) +{ + SCSIDiskState *s = opaque; + SCSIPRState *pr_state = &s->qdev.pr_state; + bool ret; + + if (!s->qdev.migrate_pr) { + return false; + } + + /* A reservation requires a key, so checking this field is enough */ + WITH_QEMU_LOCK_GUARD(&pr_state->mutex) { + ret = pr_state->key; + } + return ret; +} + +static const VMStateDescription vmstate_scsi_disk_pr_state = { + .name = "scsi-disk/pr", + .version_id = 1, + .minimum_version_id = 1, + .post_load_errp = scsi_disk_pr_state_post_load_errp, + .needed = scsi_disk_pr_state_needed, + .fields = (const VMStateField[]) { + VMSTATE_UINT64(qdev.pr_state.key, SCSIDiskState), + VMSTATE_UINT8(qdev.pr_state.resv_type, SCSIDiskState), + VMSTATE_END_OF_LIST() + } +}; +#endif /* __linux__ */ + static const VMStateDescription vmstate_scsi_disk_state = { .name = "scsi-disk", .version_id = 1, @@ -3221,7 +3261,13 @@ static const VMStateDescription vmstate_scsi_disk_state = { VMSTATE_BOOL(tray_open, SCSIDiskState), VMSTATE_BOOL(tray_locked, SCSIDiskState), VMSTATE_END_OF_LIST() - } + }, + .subsections = (const VMStateDescription * const []) { +#ifdef __linux__ + &vmstate_scsi_disk_pr_state, +#endif + NULL + }, }; static void scsi_hd_class_initfn(ObjectClass *klass, const void *data) @@ -3301,6 +3347,7 @@ static const Property scsi_block_properties[] = { -1), DEFINE_PROP_UINT32("io_timeout", SCSIDiskState, qdev.io_timeout, DEFAULT_IO_TIMEOUT), + DEFINE_PROP_BOOL("migrate-pr", SCSIDiskState, qdev.migrate_pr, true), }; static void scsi_block_class_initfn(ObjectClass *klass, const void *data) diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c index f22a38f725..2acfd21232 100644 --- a/hw/scsi/scsi-generic.c +++ b/hw/scsi/scsi-generic.c @@ -418,6 +418,89 @@ static void scsi_handle_persistent_reserve_out_reply( } } +static bool scsi_generic_pr_register(SCSIDevice *s, uint64_t key, Error **errp) +{ + uint8_t cmd[10] = {}; + uint8_t buf[24] = {}; + uint64_t key_be = cpu_to_be64(key); + int ret; + + cmd[0] = PERSISTENT_RESERVE_OUT; + cmd[1] = PRO_REGISTER; + cmd[8] = sizeof(buf); + memcpy(&buf[8], &key_be, sizeof(key_be)); + + ret = scsi_SG_IO(s->conf.blk, SG_DXFER_TO_DEV, cmd, sizeof(cmd), + buf, sizeof(buf), s->io_timeout, errp); + if (ret < 0) { + error_prepend(errp, "PERSISTENT RESERVE OUT with REGISTER"); + return false; + } + return true; +} + +static bool scsi_generic_pr_preempt(SCSIDevice *s, uint64_t key, uint8_t resv_type, Error **errp) +{ + uint8_t cmd[10] = {}; + uint8_t buf[24] = {}; + uint64_t key_be = cpu_to_be64(key); + int ret; + + cmd[0] = PERSISTENT_RESERVE_OUT; + cmd[1] = PRO_PREEMPT; + cmd[2] = resv_type & 0xf; + cmd[8] = sizeof(buf); + memcpy(&buf[0], &key_be, sizeof(key_be)); + memcpy(&buf[8], &key_be, sizeof(key_be)); + + ret = scsi_SG_IO(s->conf.blk, SG_DXFER_TO_DEV, cmd, sizeof(cmd), + buf, sizeof(buf), s->io_timeout, errp); + if (ret < 0) { + error_prepend(errp, "PERSISTENT RESERVE OUT with PREEMPT"); + return false; + } + return true; +} + +/* Register keys and preempt reservations after live migration */ +bool scsi_generic_pr_state_post_load_errp(SCSIDevice *s, Error **errp) +{ + SCSIPRState *pr_state = &s->pr_state; + uint64_t key; + uint8_t resv_type; + + WITH_QEMU_LOCK_GUARD(&pr_state->mutex) { + key = pr_state->key; + resv_type = pr_state->resv_type; + } + + trace_scsi_generic_pr_state_post_load_errp(key, resv_type); + + if (key) { + if (!scsi_generic_pr_register(s, key, errp)) { + return false; + } + + /* + * Two cases: + * + * 1. There is no reservation (resv_type is 0) and the other I_T nexus + * will be unregistered. This is important so the source host does + * not leak registered keys across live migration. + * + * 2. There is a reservation (resv_type is not 0) and the other I_T + * nexus will be unregistered and its reservation is atomically + * taken over by us. This is the scenario where a reservation is + * migrated along with the guest. + */ + if (!scsi_generic_pr_preempt(s, key, resv_type, errp)) { + return false; + } + } + /* TODO is rollback needed on the source host if migration fails after this point? */ + return true; +} + static void scsi_read_complete(void * opaque, int ret) { SCSIGenericReq *r = (SCSIGenericReq *)opaque; diff --git a/hw/scsi/trace-events b/hw/scsi/trace-events index ff92fff7c5..cff8235e9a 100644 --- a/hw/scsi/trace-events +++ b/hw/scsi/trace-events @@ -391,3 +391,4 @@ scsi_generic_aio_sgio_command(uint32_t tag, uint8_t cmd, uint32_t timeout) "gene scsi_generic_ioctl_sgio_command(uint8_t cmd, uint32_t timeout) "generic ioctl sgio: cmd=0x%x timeout=%u" scsi_generic_ioctl_sgio_done(uint8_t cmd, int ret, uint8_t status, uint8_t host_status) "generic ioctl sgio: cmd=0x%x ret=%d status=0x%x host_status=0x%x" scsi_generic_persistent_reserve_out_reply(uint8_t service_action, uint8_t resv_type, uint64_t old_key, uint64_t new_key) "persistent reserve out reply service_action=%u resv_type=%u old_key=0x%" PRIx64 " new_key=0x%" PRIx64 +scsi_generic_pr_state_post_load_errp(uint64_t key, uint8_t resv_type) "key=0x%" PRIx64 " resv_type=%u" -- 2.52.0
