• Jeremy Fitzhardinge's avatar
    xen: deal with stale cr3 values when unpinning pagetables · 9f79991d
    Jeremy Fitzhardinge authored
    When a pagetable is no longer in use, it must be unpinned so that its
    pages can be freed.  However, this is only possible if there are no
    stray uses of the pagetable.  The code currently deals with all the
    usual cases, but there's a rare case where a vcpu is changing cr3, but
    is doing so lazily, and the change hasn't actually happened by the time
    the pagetable is unpinned, even though it appears to have been completed.
    
    This change adds a second per-cpu cr3 variable - xen_current_cr3 -
    which tracks the actual state of the vcpu cr3.  It is only updated once
    the actual hypercall to set cr3 has been completed.  Other processors
    wishing to unpin a pagetable can check other vcpu's xen_current_cr3
    values to see if any cross-cpu IPIs are needed to clean things up.
    
    [ Stable folks: 2.6.23 bugfix ]
    Signed-off-by: default avatarJeremy Fitzhardinge <jeremy@xensource.com>
    Cc: Stable Kernel <stable@kernel.org>
    9f79991d
enlighten.c 28.6 KB