[V1,3/4] cpr: relax some blockers

Some devices block migration because they rely on local state that
is not migrated to the target host, such as for local filesystems.
These need not block cpr, which will restart qemu on the same host.
Narrow the scope of these blockers so they only apply to normal mode.
They will not block cpr modes when they are added in subsequent patches.

No functional change until a new mode is added.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 backends/tpm/tpm_emulator.c | 2 +-
 block/parallels.c           | 2 +-
 block/qcow.c                | 2 +-
 block/vdi.c                 | 2 +-
 block/vhdx.c                | 2 +-
 block/vmdk.c                | 2 +-
 block/vpc.c                 | 2 +-
 block/vvfat.c               | 2 +-
 hw/9pfs/9p.c                | 2 +-
 hw/scsi/vhost-scsi.c        | 2 +-
 hw/virtio/vhost.c           | 2 +-
 target/i386/nvmm/nvmm-all.c | 3 ++-
 12 files changed, 13 insertions(+), 12 deletions(-)

Steve Sistare <steven.sistare@oracle.com> wrote:
> Some devices block migration because they rely on local state that
> is not migrated to the target host, such as for local filesystems.
> These need not block cpr, which will restart qemu on the same host.
> Narrow the scope of these blockers so they only apply to normal mode.
> They will not block cpr modes when they are added in subsequent patches.
>
> No functional change until a new mode is added.
>
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

They are all basically block devices support, would be great to have a
comment from someone from the block layer.

Later, Juan.

On Thu, Oct 19, 2023 at 01:47:45PM -0700, Steve Sistare wrote:
> Some devices block migration because they rely on local state that
> is not migrated to the target host, such as for local filesystems.
> These need not block cpr, which will restart qemu on the same host.
> Narrow the scope of these blockers so they only apply to normal mode.
> They will not block cpr modes when they are added in subsequent patches.

Looking at these changes, it is not entirely clear to me
why many of these features were blocked for migration
in the first place, and thus it is even less clear why
we should be OK to relax this for cpr.

I'd prefer to see some justification for each file,
explaining why the current blocker exists and why
it is OK to relax it for cpr.

> 
> No functional change until a new mode is added.
> 
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> ---
>  backends/tpm/tpm_emulator.c | 2 +-
>  block/parallels.c           | 2 +-
>  block/qcow.c                | 2 +-
>  block/vdi.c                 | 2 +-
>  block/vhdx.c                | 2 +-
>  block/vmdk.c                | 2 +-
>  block/vpc.c                 | 2 +-
>  block/vvfat.c               | 2 +-
>  hw/9pfs/9p.c                | 2 +-
>  hw/scsi/vhost-scsi.c        | 2 +-
>  hw/virtio/vhost.c           | 2 +-
>  target/i386/nvmm/nvmm-all.c | 3 ++-
>  12 files changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/backends/tpm/tpm_emulator.c b/backends/tpm/tpm_emulator.c
> index bf1a90f..ac66aee 100644
> --- a/backends/tpm/tpm_emulator.c
> +++ b/backends/tpm/tpm_emulator.c
> @@ -534,7 +534,7 @@ static int tpm_emulator_block_migration(TPMEmulator *tpm_emu)
>          error_setg(&tpm_emu->migration_blocker,
>                     "Migration disabled: TPM emulator does not support "
>                     "migration");
> -        if (migrate_add_blocker(&tpm_emu->migration_blocker, &err) < 0) {
> +        if (migrate_add_blocker_normal(&tpm_emu->migration_blocker, &err) < 0) {
>              error_report_err(err);
>              return -1;
>          }
> diff --git a/block/parallels.c b/block/parallels.c
> index 1697a2e..8a520db 100644
> --- a/block/parallels.c
> +++ b/block/parallels.c
> @@ -1369,7 +1369,7 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
>                 bdrv_get_device_or_node_name(bs));
>      bdrv_graph_rdunlock_main_loop();
>  
> -    ret = migrate_add_blocker(&s->migration_blocker, errp);
> +    ret = migrate_add_blocker_normal(&s->migration_blocker, errp);
>      if (ret < 0) {
>          error_setg(errp, "Migration blocker error");
>          goto fail;
> diff --git a/block/qcow.c b/block/qcow.c
> index fdd4c83..eab68e3 100644
> --- a/block/qcow.c
> +++ b/block/qcow.c
> @@ -307,7 +307,7 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
>                 bdrv_get_device_or_node_name(bs));
>      bdrv_graph_rdunlock_main_loop();
>  
> -    ret = migrate_add_blocker(&s->migration_blocker, errp);
> +    ret = migrate_add_blocker_normal(&s->migration_blocker, errp);
>      if (ret < 0) {
>          goto fail;
>      }
> diff --git a/block/vdi.c b/block/vdi.c
> index fd7e365..c647d72 100644
> --- a/block/vdi.c
> +++ b/block/vdi.c
> @@ -498,7 +498,7 @@ static int vdi_open(BlockDriverState *bs, QDict *options, int flags,
>                 bdrv_get_device_or_node_name(bs));
>      bdrv_graph_rdunlock_main_loop();
>  
> -    ret = migrate_add_blocker(&s->migration_blocker, errp);
> +    ret = migrate_add_blocker_normal(&s->migration_blocker, errp);
>      if (ret < 0) {
>          goto fail_free_bmap;
>      }
> diff --git a/block/vhdx.c b/block/vhdx.c
> index e37f8c0..a9d0874 100644
> --- a/block/vhdx.c
> +++ b/block/vhdx.c
> @@ -1096,7 +1096,7 @@ static int vhdx_open(BlockDriverState *bs, QDict *options, int flags,
>      error_setg(&s->migration_blocker, "The vhdx format used by node '%s' "
>                 "does not support live migration",
>                 bdrv_get_device_or_node_name(bs));
> -    ret = migrate_add_blocker(&s->migration_blocker, errp);
> +    ret = migrate_add_blocker_normal(&s->migration_blocker, errp);
>      if (ret < 0) {
>          goto fail;
>      }
> diff --git a/block/vmdk.c b/block/vmdk.c
> index 1335d39..85864b8 100644
> --- a/block/vmdk.c
> +++ b/block/vmdk.c
> @@ -1386,7 +1386,7 @@ 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));
> -    ret = migrate_add_blocker(&s->migration_blocker, errp);
> +    ret = migrate_add_blocker_normal(&s->migration_blocker, errp);
>      if (ret < 0) {
>          goto fail;
>      }
> diff --git a/block/vpc.c b/block/vpc.c
> index c30cf86..aa1a48a 100644
> --- a/block/vpc.c
> +++ b/block/vpc.c
> @@ -452,7 +452,7 @@ static int vpc_open(BlockDriverState *bs, QDict *options, int flags,
>                 bdrv_get_device_or_node_name(bs));
>      bdrv_graph_rdunlock_main_loop();
>  
> -    ret = migrate_add_blocker(&s->migration_blocker, errp);
> +    ret = migrate_add_blocker_normal(&s->migration_blocker, errp);
>      if (ret < 0) {
>          goto fail;
>      }
> diff --git a/block/vvfat.c b/block/vvfat.c
> index 266e036..9d050ba 100644
> --- a/block/vvfat.c
> +++ b/block/vvfat.c
> @@ -1268,7 +1268,7 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
>                     "The vvfat (rw) format used by node '%s' "
>                     "does not support live migration",
>                     bdrv_get_device_or_node_name(bs));
> -        ret = migrate_add_blocker(&s->migration_blocker, errp);
> +        ret = migrate_add_blocker_normal(&s->migration_blocker, errp);
>          if (ret < 0) {
>              goto fail;
>          }
> diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> index af636cf..369dfc8 100644
> --- a/hw/9pfs/9p.c
> +++ b/hw/9pfs/9p.c
> @@ -1501,7 +1501,7 @@ static void coroutine_fn v9fs_attach(void *opaque)
>          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);
> -        err = migrate_add_blocker(&s->migration_blocker, NULL);
> +        err = migrate_add_blocker_normal(&s->migration_blocker, NULL);
>          if (err < 0) {
>              clunk_fid(s, fid);
>              goto out;
> diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c
> index 14e23cc..bf528d5 100644
> --- a/hw/scsi/vhost-scsi.c
> +++ b/hw/scsi/vhost-scsi.c
> @@ -208,7 +208,7 @@ static void vhost_scsi_realize(DeviceState *dev, Error **errp)
>                  "When external environment supports it (Orchestrator migrates "
>                  "target SCSI device state or use shared storage over network), "
>                  "set 'migratable' property to true to enable migration.");
> -        if (migrate_add_blocker(&vsc->migration_blocker, errp) < 0) {
> +        if (migrate_add_blocker_normal(&vsc->migration_blocker, errp) < 0) {
>              goto free_virtio;
>          }
>      }
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index d737671..f5e9625 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -1527,7 +1527,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
>      }
>  
>      if (hdev->migration_blocker != NULL) {
> -        r = migrate_add_blocker(&hdev->migration_blocker, errp);
> +        r = migrate_add_blocker_normal(&hdev->migration_blocker, errp);
>          if (r < 0) {
>              goto fail_busyloop;
>          }
> diff --git a/target/i386/nvmm/nvmm-all.c b/target/i386/nvmm/nvmm-all.c
> index 7d752bc..0cfcdac 100644
> --- a/target/i386/nvmm/nvmm-all.c
> +++ b/target/i386/nvmm/nvmm-all.c
> @@ -929,7 +929,8 @@ nvmm_init_vcpu(CPUState *cpu)
>          error_setg(&nvmm_migration_blocker,
>              "NVMM: Migration not supported");
>  
> -        if (migrate_add_blocker(&nvmm_migration_blocker, &local_error) < 0) {
> +        ret = migrate_add_blocker_normal(&nvmm_migration_blocker, &local_error);
> +        if (ret < 0) {
>              error_report_err(local_error);
>              return -EINVAL;
>          }
> -- 
> 1.8.3.1
> 
> 

With regards,
Daniel

On Fri, Oct 20, 2023 at 11:38:55AM +0200, Juan Quintela wrote:
> Steve Sistare <steven.sistare@oracle.com> wrote:
> > Some devices block migration because they rely on local state that
> > is not migrated to the target host, such as for local filesystems.
> > These need not block cpr, which will restart qemu on the same host.
> > Narrow the scope of these blockers so they only apply to normal mode.
> > They will not block cpr modes when they are added in subsequent patches.
> >
> > No functional change until a new mode is added.
> >
> > Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> 
> Reviewed-by: Juan Quintela <quintela@redhat.com>
> 
> They are all basically block devices support, would be great to have a
> comment from someone from the block layer.

There're also non-block ones like vhost/9pfs/..

I agree with Daniel that we should split and allow module maintainers to
review.  Maybe we can unify changes of the same module into one patch.
Even if so, some comments for each site on explaining why local migration
can skip the blocker would be greatly helpful.

Thanks,