Re: [Xen-devel] feature flags use

[Gerd Hoffmann <kraxel@xxxxxxx>]

  Hi,

> Following the need to allocate a new feature flag I soon realized that
> currently there is not even a place to store them - this to me is
> particularly puzzling for XENFEAT_pae_pgdir_above_4gb, as I would
> have expected that the CR3 handling in PAE mode gets adjusted
> according to whether the guest has that flag set. Any reason for that
> (other than *assuming* that guests without that flag will always pass
> the low 12 bits of CR3 clear)? Namely, what's the purpose of having
> the guest specify that flag if it doesn't really change anything?

Works the other way around:  The flags are xen-specfic, not guest
specific.  The guest has to check whenever xen supports pgd's above 4GB
before placing them there.

cheers,
  Gerd

-- 
Gerd Hoffmann <kraxel@xxxxxxx>
http://www.suse.de/~kraxel/julika-dora.jpeg

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