Pinning L1 page table with wrpt

Pinning L1 page table with wrpt

[Jacob Gorm Hansen]

hi,

it seems I no longer need to pin l1 pages when running with writable
page tables in xen-unstable -- e.g. I can now pin a l2 table without
having pinned its l1 descendants first, without Xen complaining. Do I
understand things correctly?

thanks,
Jacob

Re: Pinning L1 page table with wrpt

[Keir Fraser]

On 15 Aug 2005, at 09:29, Jacob Gorm Hansen wrote:

> it seems I no longer need to pin l1 pages when running with writable
> page tables in xen-unstable -- e.g. I can now pin a l2 table without
> having pinned its l1 descendants first, without Xen complaining. Do I
> understand things correctly?

Yes you do.

  -- Keir

Re: Pinning L1 page table with wrpt

[Jacob Gorm Hansen]

Keir Fraser wrote:
> 
> On 15 Aug 2005, at 09:29, Jacob Gorm Hansen wrote:
> 
>> it seems I no longer need to pin l1 pages when running with writable
>> page tables in xen-unstable -- e.g. I can now pin a l2 table without
>> having pinned its l1 descendants first, without Xen complaining. Do I
>> understand things correctly?
>
>
> Yes you do.

And then Xen will pin them for me recursively, or they will not be
pinned at all but just checked against having writable references? I
seem to have a problem when combining writable pagetables and the
traditional pinned ones in the same domain. The pagetables I inherit
from the domain builder need to be unpinned before I can use the pages
they reference for my own page tables, or I get complaints about trying
to create a writable linear p.t.

thanks,
Jacob

Re: Pinning L1 page table with wrpt

[Keir Fraser]

On 15 Aug 2005, at 09:55, Jacob Gorm Hansen wrote:

> And then Xen will pin them for me recursively, or they will not be
> pinned at all but just checked against having writable references? I
> seem to have a problem when combining writable pagetables and the
> traditional pinned ones in the same domain. The pagetables I inherit
> from the domain builder need to be unpinned before I can use the pages
> they reference for my own page tables, or I get complaints about trying
> to create a writable linear p.t.

Xen will infer their type when you pin the L2. At that point, they 
behave exactly the same as a pinned L1, until they are detached from 
the pinned L2 or the L2 itself is unpinned.

We play games with the initial p.t. in linux 2.6 as well. The code in 
arch/xen/i386/mm/init.c might be worth looking at, although it's pretty 
twisted stuff!

  -- Keir