Re: [Xen-devel] [PATCH v12 12/26] secondary vm suspend/resume/checkpoint code

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Changlong Xie writes ("[PATCH v12 12/26] secondary vm suspend/resume/checkpoint 
code"):
> From: Wen Congyang <wency@xxxxxxxxxxxxxx>

Thanks.

This is all fine except for one small thing:
> 
> +    /* COLO only supports HVM now because it does not work very
> +     * well with pv drivers:
> +     * 1. We need to resume vm in the slow path. In this case we
> +     *    need to disconnect/reconnect backend and frontend. It
> +     *    will take too much time and the performance is very slow.
> +     * 2. PV disk cannot reuse block replication that is implemented
> +     *    in QEMU.
> +     */
> +    if (info->type != LIBXL_DOMAIN_TYPE_HVM &&
> +        checkpointed_stream == LIBXL_CHECKPOINTED_STREAM_COLO) {
> +        rc = ERROR_FAIL;
> +        goto out;

In response to v11 I wrote:

> > > Please log something here, or it may be very mysterious.

I now see that you replied:

> > OK. Will add some comments to explain why only support pure HVM now.

I'm sorry that I didn't spot that emailed response from you, because
it's not what I intended.

To "log something" means to add code to print a message to the
logfile.  In general all places in libxl where an ERROR_FAIL is
generated should be accompanied by an appropriate call of a LOG macro.

There are plenty of examples in (for example) libxl_dom.c.

Your log message should include the domid.

Thanks,
Ian.

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