Re: [PATCH] xen/arm: p2m: Populate pages for GICv2 mapping in arch_domain_create()

[Xenia Ragiadakou <burzalodowa@xxxxxxxxx>]

On 10/13/22 15:39, Julien Grall wrote:
> Hi,
>
> On 13/10/2022 13:29, Henry Wang wrote:
> > > -----Original Message-----
> > > From: Jan Beulich <jbeulich@xxxxxxxx>
> > > > > Assuming you have 4 (N) page table levels, isn't it 7 (1 + 2 * (N - 
> > > > > 1))?
> > > > > Or is the root table not taken from the p2m pool?
> > > > Correct, on arm the root is not taken from the pool.
> > > Isn't that a (perhaps just minor) mistake?
> > Not really, in the code review phase, the question of whether we include
> > the root in the p2m pool was discussed and the conclusion at that time
> > was not including this page for now, as this is supposed to require a lot
> > of extra work/refactor. Probably there will be a series from my side to
> > add the root to the pool, but at least not now.
> The root page tables can be one of multiple concatenated pages (up to 8 
> pages). The P2M pool is allocating page by page and therefore wouldn't 
> allow us to allocate contiguous pages.
Sorry that I 'm asking this so late (I was just going through the 
thread) but why 8?
> Therefore, we need to handle the root differently. At which point it 
> doesn't seem to be worth it to allocate it from the P2M pool.
> Cheers,
--
Xenia