[lkml]   [2009]   [Mar]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [patch 0/6] Guest page hinting version 7.
On Fri, 27 Mar 2009 20:06:03 -0400
Rik van Riel <> wrote:

> Dave Hansen wrote:
> > On Fri, 2009-03-27 at 16:09 +0100, Martin Schwidefsky wrote:
> >> If the host picks one of the
> >> pages the guest can recreate, the host can throw it away instead of writing
> >> it to the paging device. Simple and elegant.
> >
> > Heh, simple and elegant for the hypervisor. But I'm not sure I'm going
> > to call *anything* that requires a new CPU instruction elegant. ;)
> I am convinced that it could be done with a guest-writable
> "bitmap", with 2 bits per page. That would make this scheme
> useful for KVM, too.

This was our initial approach before we came up with the milli-code
instruction. The reason we did not use a bitmap was to prevent the
guest to change the host state (4 guest states U/S/V/P and 3 host
states r/p/z). With the full set of states you'd need 4 bits. And the
hosts need to have a "master" copy of the host bits, one the guest
cannot change, otherwise you get into trouble.

blue skies,

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

 \ /
  Last update: 2009-03-29 16:23    [W:0.164 / U:0.336 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site