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    Subject[PATCH 33/50] KVM: MMU: Disable write access on clean large pages
    Date
    By forcing clean huge pages to be read-only, we have separate roles
    for the shadow of a clean large page and the shadow of a dirty large
    page. This is necessary because different ptes will be instantiated
    for the two cases, even for read faults.

    Signed-off-by: Avi Kivity <avi@qumranet.com>
    ---
    drivers/kvm/paging_tmpl.h | 2 ++
    1 files changed, 2 insertions(+), 0 deletions(-)

    diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h
    index e07cb2e..4538b15 100644
    --- a/drivers/kvm/paging_tmpl.h
    +++ b/drivers/kvm/paging_tmpl.h
    @@ -382,6 +382,8 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
    metaphysical = 1;
    hugepage_access = walker->pte;
    hugepage_access &= PT_USER_MASK | PT_WRITABLE_MASK;
    + if (!is_dirty_pte(walker->pte))
    + hugepage_access &= ~PT_WRITABLE_MASK;
    hugepage_access >>= PT_WRITABLE_SHIFT;
    if (walker->pte & PT64_NX_MASK)
    hugepage_access |= (1 << 2);
    --
    1.5.3.7


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