Re: [PATCH for-4.15] dmop: Add XEN_DMOP_nr_vcpus

[Jan Beulich <jbeulich@xxxxxxxx>]

On 25.02.2021 18:09, Andrew Cooper wrote:
> Curiously absent from the stable API/ABIs is an ability to query the number of
> vcpus which a domain has.  Emulators need to know this information in
> particular to know how many stuct ioreq's live in the ioreq server mappings.
> 
> In practice, this forces all userspace to link against libxenctrl to use
> xc_domain_getinfo(), which rather defeats the purpose of the stable libraries.
> 
> Introduce a DMOP to retrieve this information and surface it in
> libxendevicemodel to help emulators shed their use of unstable interfaces.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Hypervisor part
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
with one small adjustment:

> --- a/xen/include/xlat.lst
> +++ b/xen/include/xlat.lst
> @@ -107,6 +107,7 @@
>  ?    dm_op_set_pci_intx_level        hvm/dm_op.h
>  ?    dm_op_set_pci_link_route        hvm/dm_op.h
>  ?    dm_op_track_dirty_vram          hvm/dm_op.h
> +?    dm_op_nr_vcpus                  hvm/dm_op.h

We try to keep these sorted alphabetically, so please move the
insertion up a few lines.

Jan