Re: [Xen-devel] [PATCH v1] libxl: always call qemus xen-save-devices-state in suspend/resume

[Wei Liu <wei.liu2@xxxxxxxxxx>]

Cc Anthony.

On Thu, May 17, 2018 at 05:51:08PM +0200, Olaf Hering wrote:
> If a domU has a qemu-xen instance attached, it is required to call qemus
> "xen-save-devices-state" method. Without it, the receiving side of a PV
> migration may be unable to lock the image:
> 
> xen be: qdisk-51712: xen be: qdisk-51712: error: Failed to get "write" lock
> error: Failed to get "write" lock
> xen be: qdisk-51712: xen be: qdisk-51712: initialise() failed
> initialise() failed
> 

The commit message can use a bit of improvement. Strictly speaking, this
is only a problem when qdisk is in use.

But I think it should be harmless to issue that command anyway.

> The proper way to decide if a PV or PVH domU has a qemu-xen running is
> to use the libxl__need_xenpv_qemu API. But since there is no copy of a
> libxl_domain_config available in these places, it should be enough to
> check if xenstore contains the relevant info.
> 
> Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
> ---
>  tools/libxl/libxl_dom_suspend.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/libxl/libxl_dom_suspend.c b/tools/libxl/libxl_dom_suspend.c
> index 1e904bae8a..0d769eefd8 100644
> --- a/tools/libxl/libxl_dom_suspend.c
> +++ b/tools/libxl/libxl_dom_suspend.c
> @@ -377,7 +377,9 @@ static void 
> domain_suspend_common_guest_suspended(libxl__egc *egc,
>      libxl__ev_xswatch_deregister(gc, &dsps->guest_watch);
>      libxl__ev_time_deregister(gc, &dsps->guest_timeout);
>  
> -    if (dsps->type == LIBXL_DOMAIN_TYPE_HVM) {
> +    if (dsps->type == LIBXL_DOMAIN_TYPE_HVM ||
> +        libxl__device_model_version_running(gc, dsps->domid) ==
> +        LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN) {

You don't need to test if the guest is HVM anymore. You only need to
know if QEMU upstream is running.

Anthony, please check if I've said anything wrong.

Wei.

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