On Wed, 2008-03-12 at 15:04 -0500, Anthony Liguori wrote:

Jeremy Fitzhardinge wrote:

quoted

quoted

With stable_if_clean you are refering to stable_if_present?

No.  I misunderstood and thought that stable_if_present sets the Px 
state.  I'd overlooked the writable flag on page_set_volatile().

quoted

 If yes the
answer is that this operation is used to get a page from Vx/Px back to
Sx but only if the page has not been discarded.

So you mean it will change Vr/Pr to Sr but everything else will fail?  

In the extended version Vp/Pp to Sr as well but the current z/VM code
will discard a page if the host picks a Vr/Pr page to swap it.

Well presumably Vp/Pr => Sp?  Is is true that from the guest's 
perspective, all of the 'p' states are identical to the 'r' states?

Basically yes. The guest doesn't care about the host state.

Do the host states even really need visibility to the guest at all?  It 
may be useful for the guest to be able to distinguish between Ur and Uz 
but it doesn't seem necessary.

It is very useful for debugging to have the host state in the guest as
well. There is one possible optimization: if the guests finds a Uz page
in the free list, it can make it Sz and doesn't have to clear it because
the host will provide an already empty page (not yet implemented
though).

BTW Jeremy, the .dot was very useful!

I've search on my disk and found the state diagrams we've used for the
OLS paper. You may find these useful as well.

-- 
blue skies,
  Martin.

"Reality continues to ruin my life." - Calvin.