Re: [PATCH v4 03/14] libxc/migration: Specification update for CHECKPOINT records

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 12/05/15 12:25, Yang Hongyang wrote:
> From: Andrew Cooper <andrew.cooper3@citrix.com>
>
> Checkpointed streams need to signal the end of a consistent view of VM state,
> and the start of the libxl data.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
> CC: Ian Campbell <Ian.Campbell@citrix.com>
> CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
> CC: Wei Liu <wei.liu2@citrix.com>
> ---
>  docs/specs/libxc-migration-stream.pandoc | 33 +++++++++++++++++++++++++++++---
>  tools/libxc/xc_sr_common.c               |  1 +
>  tools/libxc/xc_sr_stream_format.h        |  1 +
>  3 files changed, 32 insertions(+), 3 deletions(-)
>
> diff --git a/docs/specs/libxc-migration-stream.pandoc b/docs/specs/libxc-migration-stream.pandoc
> index 520240f..842938c 100644
> --- a/docs/specs/libxc-migration-stream.pandoc
> +++ b/docs/specs/libxc-migration-stream.pandoc
> @@ -37,8 +37,6 @@ Not Yet Included
>  The following features are not yet fully specified and will be
>  included in a future draft.
>  
> -* Remus
> -
>  * Page data compression.
>  
>  * ARM
> @@ -227,7 +225,9 @@ type         0x00000000: END
>  
>               0x0000000D: VERIFY
>  
> -             0x0000000E - 0x7FFFFFFF: Reserved for future _mandatory_
> +             0x0000000E: CHECKPOINT
> +
> +             0x0000000F - 0x7FFFFFFF: Reserved for future _mandatory_
>               records.
>  
>               0x80000000 - 0xFFFFFFFF: Reserved for future _optional_
> @@ -578,6 +578,33 @@ The verify record contains no fields; its body_length is 0.
>  
>  \clearpage
>  
> +CHECKPOINT
> +----------
> +
> +A checkpoint record indicates that all the preceding records in the stream
> +represent a consistent view of VM state.
> +
> +     0     1     2     3     4     5     6     7 octet
> +    +-------------------------------------------------+
> +
> +The checkpoint record contains no fields; its body_length is 0
> +
> +A stream containing checkpoint records must have indicated itself as a
> +checkpointed stream in the Image Header. Conversely, a stream not
> +identified as checkpointed must not contain checkpoint records.

The above paragraph needs deleting.  It was my mistake for not deleting
it in my series.

~Andrew

> +
> +If the stream is embedded in a higher level toolstack stream, the
> +CHECKPOINT record marks the end of the libxc portion of the stream
> +and the stream is handed back to the higher level for further
> +processing.
> +
> +The higher level stream may then hand the stream back to libxc to
> +process another set of records for the next consistent VM state
> +snapshot.  This next set of records may be terminated by another
> +CHECKPOINT record or an END record.
> +
> +\clearpage
> +
>  Layout
>  ======
>  
> diff --git a/tools/libxc/xc_sr_common.c b/tools/libxc/xc_sr_common.c
> index 59e0c5d..945cfa6 100644
> --- a/tools/libxc/xc_sr_common.c
> +++ b/tools/libxc/xc_sr_common.c
> @@ -34,6 +34,7 @@ static const char *mandatory_rec_types[] =
>      [REC_TYPE_TOOLSTACK]            = "Toolstack",
>      [REC_TYPE_X86_PV_VCPU_MSRS]     = "x86 PV vcpu msrs",
>      [REC_TYPE_VERIFY]               = "Verify",
> +    [REC_TYPE_CHECKPOINT]           = "Checkpoint",
>  };
>  
>  const char *rec_type_to_str(uint32_t type)
> diff --git a/tools/libxc/xc_sr_stream_format.h b/tools/libxc/xc_sr_stream_format.h
> index d116ca6..6d0f8fd 100644
> --- a/tools/libxc/xc_sr_stream_format.h
> +++ b/tools/libxc/xc_sr_stream_format.h
> @@ -74,6 +74,7 @@ struct xc_sr_rhdr
>  #define REC_TYPE_TOOLSTACK            0x0000000bU
>  #define REC_TYPE_X86_PV_VCPU_MSRS     0x0000000cU
>  #define REC_TYPE_VERIFY               0x0000000dU
> +#define REC_TYPE_CHECKPOINT           0x0000000eU
>  
>  #define REC_TYPE_OPTIONAL             0x80000000U
>