Re: [Xen-devel] [PATCH] x86: add feature flags to shared_info page

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Mon, 2015-03-02 at 13:44 +0000, Andrew Cooper wrote:
> On 02/03/15 13:15, Jan Beulich wrote:
> >>>> On 02.03.15 at 13:59, <"jgross@xxxxxxxx".non-mime.internet> wrote:
> >> In order to indicate the Xen tools capability to support the virtual
> >> mapped linear p2m list instead the 3 level mfn tree add feature flags
> >> to the shared_info page.
> > But why in the shared info page? They'd belong to start info or should
> > be obtainable via XENVER_get_features.
> 
> Furthermore in this case, the virtual linear p2m is purely a
> guest->toolstack feature/ABI.
> 
> Xen deliberately has no knowledge of PV guest p2ms of either the 3level
> or linear variety.
> 
> Is there genuinely no better interface than the hypervisor feature flags
> to indicate a piece of toolstack support?

Per docs/misc/xenstore-paths.markdown there are platform-feature flags
in ~/control/ (multiproc suspend and xs_reset support) but that might be
available to the guest too late for this use case?

Ian.


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