KVM: MMU: Implement guest page fault bypass for nonpae

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>

1 files changed, 6 insertions, 3 deletions

diff --git a/drivers/kvm/paging_tmpl.h b/drivers/kvm/paging_tmpl.h
index bf15d127a48f..92b93134a2a6 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;