KVM: MMU: Introduce drop_spte()
When we call rmap_remove(), we (almost) always immediately follow it by
an __set_spte() to a nonpresent pte. Since we need to perform the two
operations atomically, to avoid losing the dirty and accessed bits, introduce
a helper drop_spte() and convert all call sites.
The operation is still nonatomic at this point.
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 59e750c..796a325 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -353,8 +353,7 @@
}
if (is_large_pte(*sptep)) {
- rmap_remove(vcpu->kvm, sptep);
- __set_spte(sptep, shadow_trap_nonpresent_pte);
+ drop_spte(vcpu->kvm, sptep, shadow_trap_nonpresent_pte);
kvm_flush_remote_tlbs(vcpu->kvm);
}
@@ -516,12 +515,13 @@
pte_gpa += (sptep - sp->spt) * sizeof(pt_element_t);
if (is_shadow_present_pte(*sptep)) {
- rmap_remove(vcpu->kvm, sptep);
if (is_large_pte(*sptep))
--vcpu->kvm->stat.lpages;
+ drop_spte(vcpu->kvm, sptep,
+ shadow_trap_nonpresent_pte);
need_flush = 1;
- }
- __set_spte(sptep, shadow_trap_nonpresent_pte);
+ } else
+ __set_spte(sptep, shadow_trap_nonpresent_pte);
break;
}
@@ -637,12 +637,11 @@
!is_present_gpte(gpte) || !(gpte & PT_ACCESSED_MASK)) {
u64 nonpresent;
- rmap_remove(vcpu->kvm, &sp->spt[i]);
if (is_present_gpte(gpte) || !clear_unsync)
nonpresent = shadow_trap_nonpresent_pte;
else
nonpresent = shadow_notrap_nonpresent_pte;
- __set_spte(&sp->spt[i], nonpresent);
+ drop_spte(vcpu->kvm, &sp->spt[i], nonpresent);
continue;
}