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    Subject[PATCH 40/52] KVM: MMU: Implement guest page fault bypass for nonpae
    Date
    I spent an hour worrying why I see so many guest page faults on FC6 i386.
    Turns out bypass wasn't implemented for nonpae. Implement it so it doesn't
    happen again.

    Signed-off-by: Avi Kivity <avi@qumranet.com>
    ---
    drivers/kvm/paging_tmpl.h | 9 ++++++---
    1 files changed, 6 insertions(+), 3 deletions(-)

    diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h
    index bf15d12..92b9313 100644
    --- a/drivers/kvm/paging_tmpl.h
    +++ b/drivers/kvm/paging_tmpl.h
    @@ -486,19 +486,22 @@ static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr)
    static void FNAME(prefetch_page)(struct kvm_vcpu *vcpu,
    struct kvm_mmu_page *sp)
    {
    - int i;
    + int i, offset = 0;
    pt_element_t *gpt;
    struct page *page;

    - if (sp->role.metaphysical || PTTYPE == 32) {
    + if (sp->role.metaphysical
    + || (PTTYPE == 32 && sp->role.level > PT_PAGE_TABLE_LEVEL)) {
    nonpaging_prefetch_page(vcpu, sp);
    return;
    }

    + if (PTTYPE == 32)
    + offset = sp->role.quadrant << PT64_LEVEL_BITS;
    page = gfn_to_page(vcpu->kvm, sp->gfn);
    gpt = kmap_atomic(page, KM_USER0);
    for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
    - if (is_present_pte(gpt[i]))
    + if (is_present_pte(gpt[offset + i]))
    sp->spt[i] = shadow_trap_nonpresent_pte;
    else
    sp->spt[i] = shadow_notrap_nonpresent_pte;
    --
    1.5.3.7


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