Re: [Xen-devel] [PATCH 01/10] VMX: Enable EPT A/D bit support

[Tim Deegan <tim@xxxxxxx>]

At 14:40 +0800 on 10 Apr (1428676858), Kai Huang wrote:
> > In fact, thinking about that, we should probably be setting _all_ the
> > A bits to 1, even in leaf entries, to avoid the overhead of the MMU
> > having to write them later.
> I suppose you mean A bits of leaf entries of new shattered 4K pages? Yes 
> we can, but looks it's more reasonable to inherit according to original 
> A bit of super page.

Yes, inheriting is best, but we should have already set the A bit of the
superpage to 1 as well, for the same reasons.  IOW we should set every A
bit in the whole system to 1 all the time.

BTW, this is what we do with A/D bits in normal pagetables in Xen too
-- the default is to set them all the time, so the MMU doesn't have to
fix them up later.

Cheers,

Tim.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel