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    SubjectRe: [PATCH v2 3/10] KVM: MMU: fix direct sp's access corruptted

    Avi Kivity wrote:
    > On 06/29/2010 10:45 AM, Xiao Guangrong wrote:
    >>> - there was once talk that instead of folding pt_access and pte_access
    >>> together into the leaf sp->role.access, each sp level would have its own
    >>> access permissions. In this case we don't even have to get a new direct
    >>> sp, only change the PT_DIRECTORY_LEVEL spte to add write permissions
    >>> (all direct sp's would be writeable and permissions would be controlled
    >>> at their parent_pte level). Of course that's a much bigger change than
    >>> this bug fix.
    >> Yeah, i have considered this way, but it will change the shadow page's
    >> mapping
    >> way: it control the access at the upper level, but in the current
    >> code, we allow
    >> the upper level have the ALL_ACCESS and control the access right at
    >> the last level.
    >> It will break many things, such as write-protected...
    > spte's access bits have dual purpose, both to map guest protection and
    > for host protection (like for shadowed pages, or ksm pages). So the
    > last level sptes still need to consider host write protection.

    Yeah, i see your mean, thanks, :-)

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      Last update: 2010-06-29 11:15    [W:0.043 / U:0.064 seconds]
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