Re: [Xen-devel] [PATCH v2 09/30] xen/x86: Store antifeatures inverted in a featureset

2016-02-12 Thread Jan Beulich
>>> On 12.02.16 at 17:50, wrote: > On 12/02/16 16:47, Jan Beulich wrote: > On 05.02.16 at 14:42, wrote: >>> Awkwardly, some new feature bits mean "Feature $X no longer works". >>> Store these inverted in a featureset. >>> >>> This permits safe zero-extending of a smaller featureset as part of

Re: [Xen-devel] [PATCH v2 09/30] xen/x86: Store antifeatures inverted in a featureset

2016-02-12 Thread Andrew Cooper
On 12/02/16 16:47, Jan Beulich wrote: On 05.02.16 at 14:42, wrote: >> Awkwardly, some new feature bits mean "Feature $X no longer works". >> Store these inverted in a featureset. >> >> This permits safe zero-extending of a smaller featureset as part of a >> comparison, and safe reasoning (sub

Re: [Xen-devel] [PATCH v2 09/30] xen/x86: Store antifeatures inverted in a featureset

2016-02-12 Thread Jan Beulich
>>> On 05.02.16 at 14:42, wrote: > Awkwardly, some new feature bits mean "Feature $X no longer works". > Store these inverted in a featureset. > > This permits safe zero-extending of a smaller featureset as part of a > comparison, and safe reasoning (subset?, superset?, compatible? etc.) > withou

[Xen-devel] [PATCH v2 09/30] xen/x86: Store antifeatures inverted in a featureset

2016-02-05 Thread Andrew Cooper
Awkwardly, some new feature bits mean "Feature $X no longer works". Store these inverted in a featureset. This permits safe zero-extending of a smaller featureset as part of a comparison, and safe reasoning (subset?, superset?, compatible? etc.) without specific knowldge of meaning of each bit. S