Re: [Xen-devel] [PATCH] xen: arm: implement domain_page_map_to_mfn

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-01-28 at 13:27 +0000, Jan Beulich wrote:
> >>> On 28.01.13 at 14:09, Ian Campbell <ian.campbell@xxxxxxxxxx> wrote:
> > This was recently (re?)introduced on x86 in 26447:f831d8dcf18f and is
> > now used in generic code (specifically tmem in 26454:38847c15d8cd).
> 
> So does ARM really use tmem? If not, why is it being built there?

Early on in the ARM effort I sent a patch to disable it and was shot
down.

In theory it might work. In practice I expect it will not and some
function it uses will return ENOSYS (steal_page springs to mind) so it
won't actually work.

> If so, is it really expected to work (considering that it expects all
> memory to be visible through the 1:1 mapping)?

I wasn't aware of that limitation. In that case it is very unlikely to
work!

I haven't done the 1-1 stuff for 64-bit ARM yet -- obviously when I do
tmem might at least become plausible there.

Ian.


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