Re: [Xen-devel] struct paging_mode's {write, cmpxchg}_guest_entry and guest_{map, get_eff}_l1e

[Tim Deegan <tim@xxxxxxx>]

At 09:10 -0600 on 27 Oct (1445937057), Jan Beulich wrote:
> >>> On 15.10.15 at 11:39, <tim@xxxxxxx> wrote:
> > At 02:56 -0600 on 15 Oct (1444877774), Jan Beulich wrote:
> >> what's the reason that these aren't in struct shadow_paging_mode
> >> instead? They're only being used by shadow code, and I can't see
> >> an abstract reason why HAP would ever want to use them.
> > 
> > That seems fair.  In fact AFAICT they're only called for
> > _translated-mode_ PV guests!
> > 
> > So we should just refuse to enter a translated-but-not-external paging
> > mode, since that's not maintained and almost certainly doesn't work,
> > and then these hooks can go away entirely.
> 
> Looking more closely, I think this is true for the latter two (in the
> subject), but not the former two (and indeed migration triggers
> them).

Oh, yes, I hadn't looked at those.  Yes, we need to keep
write/cmpxchg.  I would be inclined to keep them as paging-level
operations, at least as far as non-mm code is concerned.  I have no
objection to moving the function pointers into a shadow-specific
struct and having the wrapper assert that the caller is in shadow
mode.

Cheers,

Tim.

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