Re: [PATCH 0/3] xen: remove some checks for always present Xen features

[Juergen Gross]

On 22.04.21 17:23, Jan Beulich wrote:
> On 22.04.2021 17:17, Juergen Gross wrote:
> > On 22.04.21 17:16, Jan Beulich wrote:
> > > On 22.04.2021 17:10, Juergen Gross wrote:
> > > > Some features of Xen can be assumed to be always present, so add a
> > > > central check to verify this being true and remove the other checks.
> > > >
> > > > Juergen Gross (3):
> > > >     xen: check required Xen features
> > > >     xen: assume XENFEAT_mmu_pt_update_preserve_ad being set for pv guests
> > > >     xen: assume XENFEAT_gnttab_map_avail_bits being set for pv guests
> > >
> > > I wonder whether it's a good idea to infer feature presence from
> > > version numbers. If (at some point in the past) you had inferred
> > > gnttab v2 being available by version, this would have been broken
> > > by its availability becoming controllable by a command line option
> > > in Xen.
> >
> > I'm testing the feature to be really present when booting and issue a
> > message if it is not there.
>
> And how does this help if the feature really isn't there yet other code
> assumes it is?

Did you look at the features I'm testing? Those are really just low
level additions I can't imagine will ever be removed again.


Juergen

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