Re: [Xen-devel] Correct DTB compatibility for xen /hypervisor node?

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2013-01-31 at 11:53 +0000, Stefano Stabellini wrote:
> On Thu, 31 Jan 2013, Ian Campbell wrote:
> > On Wed, 2013-01-30 at 16:49 +0000, Stefano Stabellini wrote:
> > > On Mon, 28 Jan 2013, Ian Campbell wrote:
> > > > Looks like we have both 4.2 and 4.3 in use. Which should it be?
> > > > 
> > > > $ rgrep xen-4 arch/arm Documentation/
> > > > arch/arm/boot/dts/xenvm-4.2.dts:                compatible = 
> > > > "xen,xen-4.2", "xen,xen";
> > > > Documentation/devicetree/bindings/arm/xen.txt:  compatible = 
> > > > "xen,xen-4.3", "xen,xen";
> > > > 
> > > > FWIW I've always used 4.2 in my own DTB files.
> > > > 
> > > > Strictly speaking the API is the Xen 3.x API, but that doesn't seem
> > > > terribly relevant.
> > > 
> > > I have always used 4.2 too.
> > > Even though the one in xen.txt is just an example it might be worth
> > > updating with xen-4.2 to avoid confusions.
> > 
> > Or maybe we should update to 4.3 everywhere.
> > 
> > > > I suppose arch_get_xen_caps ought to return something consistent?
> > > 
> > > Right.
> > > 
> > > From my point of view, it would be useful to return a string
> > > that expresses the current hypervisor version (xen-4.3 from the Xen 4.3
> > > release, xen-4.4 from the Xen 4.4 release and so on) rather than xen-3.0.
> > > I would do the same in the compatibility node of the DTS.
> > 
> > Remember that the capability string returned by the hypervisor is not
> > exposing the version of the hypervisor -- it is exposing the version of
> > the Hypervisor *ABI*, which is a subtly different thing.
> > 
> > I think we should follow the hypervisor version until we freeze the ABI,
> > at which point we hardcode whichever version we froze at?
> 
> That's reasonable, but we shouldn't be afraid of bumping that number.

Once we have frozen the ABI we should be very afraid of bumping that
number, because it would indicate that old guests might not run...

Ian.


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