Re: Stabilising some tools only HVMOPs?

From: Wei Liu <wei.liu2@citrix.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: Wei Liu <wei.liu2@citrix.com>,
	Ian Campbell <ian.campbell@citrix.com>,
	Stefano Stabellini <stefano.stabellini@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Ian Jackson <Ian.Jackson@eu.citrix.com>,
	PaulDurrant <Paul.Durrant@citrix.com>,
	Anthony PERARD <anthony.perard@citrix.com>,
	Xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: Stabilising some tools only HVMOPs?
Date: Thu, 18 Feb 2016 10:36:28 +0000	[thread overview]
Message-ID: <20160218103628.GC3723@citrix.com> (raw)
In-Reply-To: <56C5ABA502000078000D3982@prv-mh.provo.novell.com>

On Thu, Feb 18, 2016 at 03:31:49AM -0700, Jan Beulich wrote:
> >>> On 17.02.16 at 18:28, <wei.liu2@citrix.com> wrote:
> > Hi all
> > 
> > Tools people are in the process of splitting libxenctrl into a set of
> > stable libraries. One of the proposed libraries is libxendevicemodel
> > which has a collection of APIs that can be used by device model.
> > 
> > Currently we use QEMU as reference to extract symbols and go through
> > them one by one. Along the way we discover QEMU is using some tools
> > only HVMOPs.
> > 
> > The list of tools only HVMOPs used by QEMU are:
> > 
> >   #define HVMOP_track_dirty_vram    6
> >   #define HVMOP_modified_memory    7
> >   #define HVMOP_set_mem_type    8
> >   #define HVMOP_inject_msi         16
> >   #define HVMOP_create_ioreq_server 17
> >   #define HVMOP_get_ioreq_server_info 18
> >   #define HVMOP_map_io_range_to_ioreq_server 19
> >   #define HVMOP_unmap_io_range_from_ioreq_server 20
> >   #define HVMOP_destroy_ioreq_server 21
> >   #define HVMOP_set_ioreq_server_state 22
> 
> I've just grep-ed both qemu trees, and neither appears to directly
> use any of these constants. So as long as qemu's use is solely
> through libxc interfaces, I don't see an immediate issue.
> 
> > I'm curious about the rationale for making them tools only in the
> > first place and what needs to be done to make them stable.
> 
> Qemu, in the original consideration, may also have been deemed
> part of the tools.
> 
> > The option to build stable library APIs on top of unstable hypervisor
> > APIs is always there, but that looks suboptimal to me.
> 
> Well, as long as we continue to tie libxc to the hypervisor version,
> I think hiding versioning issues there would be fine.
> 

I think you missed the first part of my email -- we are trying to split
part of libxc out to make it stable.  Ian's reply in a sibling thread
has made clear the rationale behind this.  

Libxc is still tied to hypervisor, but the libraries that we split out
are stable.

Wei.

> Jan
> 