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Re: [Qemu-block] [PATCH v3 1/1] migration: disallow migrate_add_blocker
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From: |
Greg Kurz |
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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 11:52:50 +0100 |
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. :)
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)