Re: [Xen-devel] [PATCH v5 17/23] x86/mm: export base_disallow_mask and l1 mask in asm-x86/mm.h

[Tim Deegan <tim@xxxxxxx>]

At 07:52 -0600 on 22 Sep (1506066733), Jan Beulich wrote:
> >>> On 14.09.17 at 14:58, <wei.liu2@xxxxxxxxxx> wrote:
> > The l1 mask needs to stay in x86/mm.c while l{2,3,4} masks are only
> > needed by PV code. Both x86 common mm code and PV mm code use
> > base_disallow_mask and l1 maks.
> > 
> > Export base_disallow_mask and l1 mask in asm-x86/mm.h.
> 
> So that's because in patch 20 you need to keep
> get_page_from_l1e() in x86/mm.c, due to being used by shadow
> code. But is shadow using the same disallow mask for HVM guests
> actually correct? Perhaps it would be better for callers of
> get_page_from_l1e() to pass in their disallow masks, even if it
> would just so happen that PV and shadow use the same ones?
> Tim, do you have any thoughts or insights here?

IIRC the shadow code isn't relying on the disallow mask for anything
in HVM guests; it's built the shadows according to its own rules.

I don't think that anything's improved by making the disallow mask
explicit but I have no objection to it if it makes other refactoring
simpler.

Tim.

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