Re: [patch 2/5] KVM: MMU: allow pinning spte translations (TDP-only)

[Gleb Natapov <gleb@minantech.com>]

On Thu, Jun 19, 2014 at 04:22:57PM -0300, Marcelo Tosatti wrote:
> On Thu, Jun 19, 2014 at 10:21:16AM +0300, Gleb Natapov wrote:
> > On Wed, Jun 18, 2014 at 08:12:05PM -0300, mtosatti@redhat.com wrote:
> > > Allow vcpus to pin spte translations by:
> > > 
> > > 1) Creating a per-vcpu list of pinned ranges.
> > What if memory slot containing pinned range is going away?
> 
> ->page_fault() should fail and guest abort. Will double check.
> 
> > > 2) On mmu reload request:
> > > 	- Fault ranges.
> > > 	- Mark sptes with a pinned bit.
> > Should also be marked "dirty" as per SDM:
> >  The three DS save area sections should be allocated from a non-paged pool, and marked accessed and dirty
> 
> This (SDM text) is about guest pagetable AFAICS.
> 
Its hard to say. SDM does not mention virtualization or two dimensional
paging in that section at all. My reading is that this section talks about
all translations that CPU should perform to get to the physical address,
otherwise why are we trying hard to make sure that EPT translations are
always present? Because the same paragraph say in the next sentence:

 It is the responsibility of the operating system to keep the pages that
 contain the buffer present and to mark them accessed and dirty

So it we take from it that translation should be present the same goes for
accessed and dirty. If Andi can clarify this within Intel it would be great.

--
			Gleb.