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    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:0.037 / U:7.076 seconds]
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