Re: [Xen-devel] [PATCH v2] x86/mm: Add mem access rights to NPT

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Fri, Jun 29, 2018 at 3:38 AM Jan Beulich <JBeulich@xxxxxxxx> wrote:
>
> >>> On 29.06.18 at 10:42, <aisaila@xxxxxxxxxxxxxxx> wrote:
> > I've started a win 7 machine with no introspection or xen-access. After
> > 30 min of uptime there were 0 inserts into the tree. I guess the
> > overhead is down to a minimum with no user modified access rights.
>
> Thanks, this is helpful to know. In that case though, as said before, I'd
> like to ask to defer setting up of the radix tree to the point where it
> actually is going to be needed.

Are you worried about the radix tree being present (ie radix_tree_init
have been called) before it is used for mem_access? As I said earlier,
a lookup on an empty radix tree is equivalent of a NULL check. I don't
get how not having the tree initialized will be any faster then doing
a lookup on an empty one.

Tamas

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