Re: [Xen-devel] [PATCH XEN v4 04/23] tools: Refactor /dev/xen/evtchn wrappers into libxenevtchn.

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Oct 21, 2015 at 04:23:11PM +0100, Ian Campbell wrote:
> libxenevtchn will provide a stable API and ABI for accessing the
> evtchn device.
> 
> The functions are moved into the xenevtchn namespace to make a clean
> break from libxc and avoid ambiguity regarding which interfaces are
> stable.
> 
> All in-tree users are updated to use the new names.
> 
> Upon request (via #define XC_WANT_COMPAT_EVTCHN_API) libxenctrl will
> provide a compat API for the old names. This is used by qemu-xen for
> the time being. qemu-xen-traditional is updated in lockstep.
> 
> This leaves a few event channel related functions which go via privcmd
> (EVTCHNOP) rather than ioctls on the /dev/xen/evtchn device in
> libxenctrl. Specifically:
> 
>  - xc_evtchn_alloc_unbound
>  - xc_evtchn_reset
>  - xc_evtchn_status
> 
> Note that xc_evtchn_alloc_unbound's functionality is also provided by
> xenevtchn_bind_unbound_port() (née xc_evtchn_bind_unbound_port) and is
> probably redundant.
> 
> These functions do not appear to be needed by qemu-dm, qemu-pv
> (provision of device model to HVM guests and PV backends respectively)
> or by libvchan suggesting they are not needed by non-toolstack uses of
> event channels. QEMU does use these in hw/xenpv/xen_domainbuild.c but
> that is a "toolstack use".
> 
> The new library uses a version script to ensure that only expected
> symbols are exported and to version them such that ABI guarantees can
> be kept in the future.
> 
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>

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