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Re: [Qemu-block] [PATCH v3 1/1] migration: disallow migrate_add_blocker
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From: |
Dr. David Alan Gilbert |
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Subject: |
Re: [Qemu-block] [PATCH v3 1/1] migration: disallow migrate_add_blocker during migration |
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Date: |
Mon, 12 Dec 2016 11:02:54 +0000 |
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User-agent: |
Mutt/1.7.1 (2016-10-04) |
* Greg Kurz (address@hidden) wrote:
> On Fri, 9 Dec 2016 12:25:47 -0500
> John Snow <address@hidden> wrote:
>
> > If a migration is already in progress and somebody attempts
> > to add a migration blocker, this should rightly fail.
> >
> > Add an errp parameter and a retcode return value to migrate_add_blocker.
> >
> > Signed-off-by: John Snow <address@hidden>
> > ---
> > block/qcow.c | 6 +++++-
> > block/vdi.c | 6 +++++-
> > block/vhdx.c | 24 ++++++++++++++----------
> > block/vmdk.c | 7 ++++++-
> > block/vpc.c | 10 +++++++---
> > block/vvfat.c | 20 ++++++++++++--------
> > hw/9pfs/9p.c | 16 ++++++++++++----
> > hw/display/virtio-gpu.c | 29 ++++++++++++++++-------------
> > hw/misc/ivshmem.c | 11 +++++++----
> > hw/scsi/vhost-scsi.c | 25 +++++++++++++++++++------
> > hw/virtio/vhost.c | 8 +++++++-
> > include/migration/migration.h | 6 +++++-
> > migration/migration.c | 35 +++++++++++++++++++++++++++++++++--
> > stubs/migr-blocker.c | 3 ++-
> > target-i386/kvm.c | 16 +++++++++++++---
> > 15 files changed, 163 insertions(+), 59 deletions(-)
> >
> > diff --git a/block/qcow.c b/block/qcow.c
> > index 7540f43..11526a1 100644
> > --- a/block/qcow.c
> > +++ b/block/qcow.c
> > @@ -252,7 +252,11 @@ static int qcow_open(BlockDriverState *bs, QDict
> > *options, int flags,
> > error_setg(&s->migration_blocker, "The qcow format used by node '%s' "
> > "does not support live migration",
> > bdrv_get_device_or_node_name(bs));
> > - migrate_add_blocker(s->migration_blocker);
> > + ret = migrate_add_blocker(s->migration_blocker, errp);
> > + if (ret < 0) {
> > + error_free(s->migration_blocker);
> > + goto fail;
> > + }
> >
> > qemu_co_mutex_init(&s->lock);
> > return 0;
> > diff --git a/block/vdi.c b/block/vdi.c
> > index 96b78d5..2b56f52 100644
> > --- a/block/vdi.c
> > +++ b/block/vdi.c
> > @@ -471,7 +471,11 @@ static int vdi_open(BlockDriverState *bs, QDict
> > *options, int flags,
> > error_setg(&s->migration_blocker, "The vdi format used by node '%s' "
> > "does not support live migration",
> > bdrv_get_device_or_node_name(bs));
> > - migrate_add_blocker(s->migration_blocker);
> > + ret = migrate_add_blocker(s->migration_blocker, errp);
> > + if (ret < 0) {
> > + error_free(s->migration_blocker);
> > + goto fail_free_bmap;
> > + }
> >
> > qemu_co_mutex_init(&s->write_lock);
> >
> > diff --git a/block/vhdx.c b/block/vhdx.c
> > index 0ba2f0a..d81941b 100644
> > --- a/block/vhdx.c
> > +++ b/block/vhdx.c
> > @@ -991,20 +991,24 @@ static int vhdx_open(BlockDriverState *bs, QDict
> > *options, int flags,
> > }
> > }
> >
> > - if (flags & BDRV_O_RDWR) {
> > - ret = vhdx_update_headers(bs, s, false, NULL);
> > - if (ret < 0) {
> > - goto fail;
> > - }
> > - }
> > -
> > - /* TODO: differencing files */
> > -
> > /* Disable migration when VHDX images are used */
> > error_setg(&s->migration_blocker, "The vhdx format used by node '%s' "
> > "does not support live migration",
> > bdrv_get_device_or_node_name(bs));
> > - migrate_add_blocker(s->migration_blocker);
> > + ret = migrate_add_blocker(s->migration_blocker, errp);
> > + if (ret < 0) {
> > + error_free(s->migration_blocker);
> > + goto fail;
> > + }
> > +
> > + if (flags & BDRV_O_RDWR) {
> > + ret = vhdx_update_headers(bs, s, false, NULL);
> > + if (ret < 0) {
> > + goto fail;
> > + }
> > + }
> > +
> > + /* TODO: differencing files */
> >
> > return 0;
> > fail:
> > diff --git a/block/vmdk.c b/block/vmdk.c
> > index a11c27a..4a45a83 100644
> > --- a/block/vmdk.c
> > +++ b/block/vmdk.c
> > @@ -976,7 +976,12 @@ static int vmdk_open(BlockDriverState *bs, QDict
> > *options, int flags,
> > error_setg(&s->migration_blocker, "The vmdk format used by node '%s' "
> > "does not support live migration",
> > bdrv_get_device_or_node_name(bs));
> > - migrate_add_blocker(s->migration_blocker);
> > + ret = migrate_add_blocker(s->migration_blocker, errp);
> > + if (ret < 0) {
> > + error_free(s->migration_blocker);
> > + goto fail;
> > + }
> > +
> > g_free(buf);
> > return 0;
> >
> > diff --git a/block/vpc.c b/block/vpc.c
> > index 8d5886f..299a8c8 100644
> > --- a/block/vpc.c
> > +++ b/block/vpc.c
> > @@ -422,13 +422,17 @@ static int vpc_open(BlockDriverState *bs, QDict
> > *options, int flags,
> > #endif
> > }
> >
> > - qemu_co_mutex_init(&s->lock);
> > -
> > /* Disable migration when VHD images are used */
> > error_setg(&s->migration_blocker, "The vpc format used by node '%s' "
> > "does not support live migration",
> > bdrv_get_device_or_node_name(bs));
> > - migrate_add_blocker(s->migration_blocker);
> > + ret = migrate_add_blocker(s->migration_blocker, errp);
> > + if (ret < 0) {
> > + error_free(s->migration_blocker);
> > + goto fail;
> > + }
> > +
> > + qemu_co_mutex_init(&s->lock);
> >
> > return 0;
> >
> > diff --git a/block/vvfat.c b/block/vvfat.c
> > index ded2109..3de3320 100644
> > --- a/block/vvfat.c
> > +++ b/block/vvfat.c
> > @@ -1185,22 +1185,26 @@ static int vvfat_open(BlockDriverState *bs, QDict
> > *options, int flags,
> >
> > s->sector_count = s->faked_sectors +
> > s->sectors_per_cluster*s->cluster_count;
> >
> > - if (s->first_sectors_number == 0x40) {
> > - init_mbr(s, cyls, heads, secs);
> > - }
> > -
> > - // assert(is_consistent(s));
> > - qemu_co_mutex_init(&s->lock);
> > -
> > /* Disable migration when vvfat is used rw */
> > if (s->qcow) {
> > error_setg(&s->migration_blocker,
> > "The vvfat (rw) format used by node '%s' "
> > "does not support live migration",
> > bdrv_get_device_or_node_name(bs));
> > - migrate_add_blocker(s->migration_blocker);
> > + ret = migrate_add_blocker(s->migration_blocker, errp);
> > + if (ret < 0) {
> > + error_free(s->migration_blocker);
> > + goto fail;
> > + }
> > }
> >
> > + if (s->first_sectors_number == 0x40) {
> > + init_mbr(s, cyls, heads, secs);
> > + }
> > +
> > + // assert(is_consistent(s));
> > + qemu_co_mutex_init(&s->lock);
> > +
> > ret = 0;
> > fail:
> > qemu_opts_del(opts);
> > diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> > index faebd91..e72ef43 100644
> > --- a/hw/9pfs/9p.c
> > +++ b/hw/9pfs/9p.c
> > @@ -1013,20 +1013,28 @@ static void coroutine_fn v9fs_attach(void *opaque)
> > goto out;
> > }
> > err += offset;
> > - memcpy(&s->root_qid, &qid, sizeof(qid));
> > - trace_v9fs_attach_return(pdu->tag, pdu->id,
> > - qid.type, qid.version, qid.path);
> > +
> > /*
> > * disable migration if we haven't done already.
> > * attach could get called multiple times for the same export.
> > */
> > if (!s->migration_blocker) {
> > + int ret;
> > s->root_fid = fid;
> > error_setg(&s->migration_blocker,
> > "Migration is disabled when VirtFS export path '%s' is
> > mounted in the guest using mount_tag '%s'",
> > s->ctx.fs_root ? s->ctx.fs_root : "NULL", s->tag);
> > - migrate_add_blocker(s->migration_blocker);
> > + ret = migrate_add_blocker(s->migration_blocker, NULL);
> > + if (ret < 0) {
> > + err = ret;
> > + clunk_fid(s, fid);
> > + goto out;
>
> So this would cause mount(2) in the guest to fail with EBUSY if
> migration is in progress, right ? I guess well configured guests
> should be able to cope with temporary failures when mounting
> a network filesystem and retry later.
>
> I don't object but I'd like to have some more background... if
> you could point me to the on-list discussion you're mentioning
> in the cover letter, that'd be great. :)
See the discussion on:
https://lists.nongnu.org/archive/html/qemu-devel/2016-12/msg01185.html
note, it might be best to special case 9pfs here; it's unusual
in that it's unusable in that it always does the migration blocker
when in use; everywhere else has the flag in the VMStateDescription
or only blocks in specific cases.
Dave
> Thanks.
>
> --
> Greg
>
> > + }
> > }
> > +
> > + memcpy(&s->root_qid, &qid, sizeof(qid));
> > + trace_v9fs_attach_return(pdu->tag, pdu->id,
> > + qid.type, qid.version, qid.path);
> > out:
> > put_fid(pdu, fidp);
> > out_nofid:
> > diff --git a/hw/display/virtio-gpu.c b/hw/display/virtio-gpu.c
> > index 5f32e1a..6e60b8c 100644
> > --- a/hw/display/virtio-gpu.c
> > +++ b/hw/display/virtio-gpu.c
> > @@ -1108,14 +1108,6 @@ static void virtio_gpu_device_realize(DeviceState
> > *qdev, Error **errp)
> > return;
> > }
> >
> > - g->config_size = sizeof(struct virtio_gpu_config);
> > - g->virtio_config.num_scanouts = g->conf.max_outputs;
> > - virtio_init(VIRTIO_DEVICE(g), "virtio-gpu", VIRTIO_ID_GPU,
> > - g->config_size);
> > -
> > - g->req_state[0].width = 1024;
> > - g->req_state[0].height = 768;
> > -
> > g->use_virgl_renderer = false;
> > #if !defined(CONFIG_VIRGL) || defined(HOST_WORDS_BIGENDIAN)
> > have_virgl = false;
> > @@ -1127,6 +1119,22 @@ static void virtio_gpu_device_realize(DeviceState
> > *qdev, Error **errp)
> > }
> >
> > if (virtio_gpu_virgl_enabled(g->conf)) {
> > + error_setg(&g->migration_blocker, "virgl is not yet migratable");
> > + if (migrate_add_blocker(g->migration_blocker, errp) < 0) {
> > + error_free(g->migration_blocker);
> > + return;
> > + }
> > + }
> > +
> > + g->config_size = sizeof(struct virtio_gpu_config);
> > + g->virtio_config.num_scanouts = g->conf.max_outputs;
> > + virtio_init(VIRTIO_DEVICE(g), "virtio-gpu", VIRTIO_ID_GPU,
> > + g->config_size);
> > +
> > + g->req_state[0].width = 1024;
> > + g->req_state[0].height = 768;
> > +
> > + if (virtio_gpu_virgl_enabled(g->conf)) {
> > /* use larger control queue in 3d mode */
> > g->ctrl_vq = virtio_add_queue(vdev, 256,
> > virtio_gpu_handle_ctrl_cb);
> > g->cursor_vq = virtio_add_queue(vdev, 16,
> > virtio_gpu_handle_cursor_cb);
> > @@ -1152,11 +1160,6 @@ static void virtio_gpu_device_realize(DeviceState
> > *qdev, Error **errp)
> > dpy_gfx_replace_surface(g->scanout[i].con, NULL);
> > }
> > }
> > -
> > - if (virtio_gpu_virgl_enabled(g->conf)) {
> > - error_setg(&g->migration_blocker, "virgl is not yet migratable");
> > - migrate_add_blocker(g->migration_blocker);
> > - }
> > }
> >
> > static void virtio_gpu_device_unrealize(DeviceState *qdev, Error **errp)
> > diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
> > index abeaf3d..585cc5b 100644
> > --- a/hw/misc/ivshmem.c
> > +++ b/hw/misc/ivshmem.c
> > @@ -903,9 +903,6 @@ static void ivshmem_common_realize(PCIDevice *dev,
> > Error **errp)
> > }
> > }
> >
> > - vmstate_register_ram(s->ivshmem_bar2, DEVICE(s));
> > - pci_register_bar(PCI_DEVICE(s), 2, attr, s->ivshmem_bar2);
> > -
> > if (s->master == ON_OFF_AUTO_AUTO) {
> > s->master = s->vm_id == 0 ? ON_OFF_AUTO_ON : ON_OFF_AUTO_OFF;
> > }
> > @@ -913,8 +910,14 @@ static void ivshmem_common_realize(PCIDevice *dev,
> > Error **errp)
> > if (!ivshmem_is_master(s)) {
> > error_setg(&s->migration_blocker,
> > "Migration is disabled when using feature 'peer mode'
> > in device 'ivshmem'");
> > - migrate_add_blocker(s->migration_blocker);
> > + if (migrate_add_blocker(s->migration_blocker, errp) < 0) {
> > + error_free(s->migration_blocker);
> > + return;
> > + }
> > }
> > +
> > + vmstate_register_ram(s->ivshmem_bar2, DEVICE(s));
> > + pci_register_bar(PCI_DEVICE(s), 2, attr, s->ivshmem_bar2);
> > }
> >
> > static void ivshmem_exit(PCIDevice *dev)
> > diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c
> > index 5b26946..ff503d0 100644
> > --- a/hw/scsi/vhost-scsi.c
> > +++ b/hw/scsi/vhost-scsi.c
> > @@ -238,8 +238,14 @@ static void vhost_scsi_realize(DeviceState *dev, Error
> > **errp)
> > vhost_dummy_handle_output);
> > if (err != NULL) {
> > error_propagate(errp, err);
> > - close(vhostfd);
> > - return;
> > + goto close_fd;
> > + }
> > +
> > + error_setg(&s->migration_blocker,
> > + "vhost-scsi does not support migration");
> > + ret = migrate_add_blocker(s->migration_blocker, errp);
> > + if (ret < 0) {
> > + goto free_blocker;
> > }
> >
> > s->dev.nvqs = VHOST_SCSI_VQ_NUM_FIXED + vs->conf.num_queues;
> > @@ -252,7 +258,7 @@ static void vhost_scsi_realize(DeviceState *dev, Error
> > **errp)
> > if (ret < 0) {
> > error_setg(errp, "vhost-scsi: vhost initialization failed: %s",
> > strerror(-ret));
> > - return;
> > + goto free_vqs;
> > }
> >
> > /* At present, channel and lun both are 0 for bootable vhost-scsi disk
> > */
> > @@ -261,9 +267,16 @@ static void vhost_scsi_realize(DeviceState *dev, Error
> > **errp)
> > /* Note: we can also get the minimum tpgt from kernel */
> > s->target = vs->conf.boot_tpgt;
> >
> > - error_setg(&s->migration_blocker,
> > - "vhost-scsi does not support migration");
> > - migrate_add_blocker(s->migration_blocker);
> > + return;
> > +
> > + free_vqs:
> > + migrate_del_blocker(s->migration_blocker);
> > + g_free(s->dev.vqs);
> > + free_blocker:
> > + error_free(s->migration_blocker);
> > + close_fd:
> > + close(vhostfd);
> > + return;
> > }
> >
> > static void vhost_scsi_unrealize(DeviceState *dev, Error **errp)
> > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> > index f7f7023..416fada 100644
> > --- a/hw/virtio/vhost.c
> > +++ b/hw/virtio/vhost.c
> > @@ -1157,7 +1157,13 @@ int vhost_dev_init(struct vhost_dev *hdev, void
> > *opaque,
> > }
> >
> > if (hdev->migration_blocker != NULL) {
> > - migrate_add_blocker(hdev->migration_blocker);
> > + Error *local_err;
> > + r = migrate_add_blocker(hdev->migration_blocker, &local_err);
> > + if (r < 0) {
> > + error_report_err(local_err);
> > + error_free(hdev->migration_blocker);
> > + goto fail_busyloop;
> > + }
> > }
> >
> > hdev->mem = g_malloc0(offsetof(struct vhost_memory, regions));
> > diff --git a/include/migration/migration.h b/include/migration/migration.h
> > index c309d23..8a91215 100644
> > --- a/include/migration/migration.h
> > +++ b/include/migration/migration.h
> > @@ -240,6 +240,7 @@ void remove_migration_state_change_notifier(Notifier
> > *notify);
> > MigrationState *migrate_init(const MigrationParams *params);
> > bool migration_is_blocked(Error **errp);
> > bool migration_in_setup(MigrationState *);
> > +bool migration_is_idle(MigrationState *s);
> > bool migration_has_finished(MigrationState *);
> > bool migration_has_failed(MigrationState *);
> > /* True if outgoing migration has entered postcopy phase */
> > @@ -284,8 +285,11 @@ int ram_postcopy_incoming_init(MigrationIncomingState
> > *mis);
> > * @migrate_add_blocker - prevent migration from proceeding
> > *
> > * @reason - an error to be returned whenever migration is attempted
> > + * @errp - [out] The reason (if any) we cannot block migration right now.
> > + *
> > + * @returns - 0 on success, -EBUSY on failure, with errp set.
> > */
> > -void migrate_add_blocker(Error *reason);
> > +int migrate_add_blocker(Error *reason, Error **errp);
> >
> > /**
> > * @migrate_del_blocker - remove a blocking error from migration
> > diff --git a/migration/migration.c b/migration/migration.c
> > index f498ab8..713e012 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -1044,6 +1044,31 @@ bool
> > migration_in_postcopy_after_devices(MigrationState *s)
> > return migration_in_postcopy(s) && s->postcopy_after_devices;
> > }
> >
> > +bool migration_is_idle(MigrationState *s)
> > +{
> > + if (!s) {
> > + s = migrate_get_current();
> > + }
> > +
> > + switch (s->state) {
> > + case MIGRATION_STATUS_NONE:
> > + case MIGRATION_STATUS_CANCELLED:
> > + case MIGRATION_STATUS_COMPLETED:
> > + case MIGRATION_STATUS_FAILED:
> > + return true;
> > + case MIGRATION_STATUS_SETUP:
> > + case MIGRATION_STATUS_CANCELLING:
> > + case MIGRATION_STATUS_ACTIVE:
> > + case MIGRATION_STATUS_POSTCOPY_ACTIVE:
> > + case MIGRATION_STATUS_COLO:
> > + return false;
> > + case MIGRATION_STATUS__MAX:
> > + g_assert_not_reached();
> > + }
> > +
> > + return false;
> > +}
> > +
> > MigrationState *migrate_init(const MigrationParams *params)
> > {
> > MigrationState *s = migrate_get_current();
> > @@ -1086,9 +1111,15 @@ MigrationState *migrate_init(const MigrationParams
> > *params)
> >
> > static GSList *migration_blockers;
> >
> > -void migrate_add_blocker(Error *reason)
> > +int migrate_add_blocker(Error *reason, Error **errp)
> > {
> > - migration_blockers = g_slist_prepend(migration_blockers, reason);
> > + if (migration_is_idle(NULL)) {
> > + migration_blockers = g_slist_prepend(migration_blockers, reason);
> > + return 0;
> > + }
> > +
> > + error_setg(errp, "Cannot block a migration already in-progress");
> > + return -EBUSY;
> > }
> >
> > void migrate_del_blocker(Error *reason)
> > diff --git a/stubs/migr-blocker.c b/stubs/migr-blocker.c
> > index 8ab3604..a5ba18f 100644
> > --- a/stubs/migr-blocker.c
> > +++ b/stubs/migr-blocker.c
> > @@ -2,8 +2,9 @@
> > #include "qemu-common.h"
> > #include "migration/migration.h"
> >
> > -void migrate_add_blocker(Error *reason)
> > +int migrate_add_blocker(Error *reason, Error **errp)
> > {
> > + return 0;
> > }
> >
> > void migrate_del_blocker(Error *reason)
> > diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> > index f62264a..8abb54d 100644
> > --- a/target-i386/kvm.c
> > +++ b/target-i386/kvm.c
> > @@ -961,7 +961,11 @@ int kvm_arch_init_vcpu(CPUState *cs)
> > error_setg(&invtsc_mig_blocker,
> > "State blocked by non-migratable CPU device"
> > " (invtsc flag)");
> > - migrate_add_blocker(invtsc_mig_blocker);
> > + r = migrate_add_blocker(invtsc_mig_blocker, NULL);
> > + if (r < 0) {
> > + fprintf(stderr, "migrate_add_blocker failed\n");
> > + goto efail;
> > + }
> > /* for savevm */
> > vmstate_x86_cpu.unmigratable = 1;
> > }
> > @@ -969,12 +973,12 @@ int kvm_arch_init_vcpu(CPUState *cs)
> > cpuid_data.cpuid.padding = 0;
> > r = kvm_vcpu_ioctl(cs, KVM_SET_CPUID2, &cpuid_data);
> > if (r) {
> > - return r;
> > + goto fail;
> > }
> >
> > r = kvm_arch_set_tsc_khz(cs);
> > if (r < 0) {
> > - return r;
> > + goto fail;
> > }
> >
> > /* vcpu's TSC frequency is either specified by user, or following
> > @@ -1001,6 +1005,12 @@ int kvm_arch_init_vcpu(CPUState *cs)
> > }
> >
> > return 0;
> > +
> > + fail:
> > + migrate_del_blocker(invtsc_mig_blocker);
> > + efail:
> > + error_free(invtsc_mig_blocker);
> > + return r;
> > }
> >
> > void kvm_arch_reset_vcpu(X86CPU *cpu)
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK