Re: [PATCH v3 COLOPre 11/26] tools/libxl: introduce a new API libxl__domain_restore() to load qemu state

[Ian Campbell <ian.campbell@citrix.com>]

On Thu, 2015-06-25 at 14:25 +0800, Yang Hongyang wrote:
> Secondary vm is running in colo mode. So we will do
> the following things again and again:
> 1. suspend both primay vm and secondary vm
> 2. sync the state
> 3. resume both primary vm and secondary vm
> We will send qemu's state each time in step2, and
> slave's qemu should read it each time before resuming
> secondary vm. Introduce a new API libxl__domain_restore()
> to do it. This API should be called before resuming
> secondary vm.

I think before this patch the state was passed to qemu as a parameter
when it was launched, is that correct? If so then that would be worth
mentioning for completeness.

> Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
> Cc: Anthony Perard <anthony.perard@citrix.com>
> ---
>  tools/libxl/libxl_dom_save.c | 49 ++++++++++++++++++++++++++++++++++++++++++++
>  tools/libxl/libxl_internal.h |  3 +++
>  tools/libxl/libxl_qmp.c      | 10 +++++++++
>  3 files changed, 62 insertions(+)
> 
> diff --git a/tools/libxl/libxl_dom_save.c b/tools/libxl/libxl_dom_save.c
> index 8fe1625..0ad2894 100644
> --- a/tools/libxl/libxl_dom_save.c
> +++ b/tools/libxl/libxl_dom_save.c
> @@ -639,6 +639,55 @@ int libxl__toolstack_restore(uint32_t domid, const uint8_t *buf,
>      }
>      return 0;
>  }
> +
> +static int libxl__domain_restore_device_model(libxl__gc *gc, uint32_t domid);
> +
> +int libxl__domain_restore(libxl__gc *gc, uint32_t domid)

We don't have any libxl__domain_save counterpart, but we do have
libxl__domain_save_device_model, so I wonder if the upcoming callers
ought to just call that direct? Especially given that this function
isn't any kind of generic domain restore, but has rather specific
functionality (in particular it fails for PV guests).