Re: [Xen-devel] [PATCH 3/3] libxc/migrationv2: Split {start, end}_of_stream() to make checkpoint variants

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 08/05/15 14:30, Ian Campbell wrote:
> On Fri, 2015-05-08 at 13:54 +0100, Andrew Cooper wrote:
>> This is in preparation for supporting checkpointed streams in migration v2.
>>  - For PV guests, the VCPU context is moved to end_of_checkpoint().
>>  - For HVM guests, the HVM context and params are moved to 
>> end_of_checkpoint().
> [...]
>> +    /**
>> +     * Send records which need to be at the end of the checkpoint.  This is
>> +     * called once, or once per checkpoint in a checkpointed stream, and is
>> +     * after the memory data.
>> +     */
>> +    int (*end_of_checkpoint)(struct xc_sr_context *ctx);
>> +
>> +    /**
>> +     * Send records which need to be at the end of the stream.  This is 
>> called
>> +     * once, before the END record is written.
>>       */
>>      int (*end_of_stream)(struct xc_sr_context *ctx);
> [...]
>> +static int x86_hvm_end_of_stream(struct xc_sr_context *ctx)
>> +{
>> +    int rc;
>> +
>> +    rc = write_tsc_info(ctx);
>>      if ( rc )
>>          return rc;
>>  
>> -    /* Write HVM_PARAMS record contains applicable HVM params. */
>> -    rc = write_hvm_params(ctx);
>> +#ifdef XG_LIBXL_HVM_COMPAT
>> +    rc = write_toolstack(ctx);
> I'm not sure about this end_of_stream thing. In a check pointing for
> fault tolerance scenario (Remus or COLO) then failover happens when the
> sender has died for some reason, and therefore won't get the chance to
> send any end of stream stuff.

Does Remus currently function if the sending toolstack suddenly
disappears out of the mix?

Although on consideration, I do agree that end_of_stream() shouldn't
really be a thing.

>
> IOW I think everything in end_of_stream actually needs to be in
> end_of_checkpoint unless it is just for informational purposes in a
> regular migration or something (which write_toolstack surely isn't)

There are some side effects which I will have to work around, but I will
see what I can do.

~Andrew

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