{
struct kvm_mmu_page *sp = sptep_to_sp(pt);
int level = sp->role.level;
- gfn_t gfn = sp->gfn;
+ gfn_t base_gfn = sp->gfn;
u64 old_child_spte;
u64 *sptep;
+ gfn_t gfn;
int i;
trace_kvm_mmu_prepare_zap_page(sp);
for (i = 0; i < PT64_ENT_PER_PAGE; i++) {
sptep = pt + i;
+ gfn = base_gfn + (i * KVM_PAGES_PER_HPAGE(level - 1));
if (shared) {
- old_child_spte = xchg(sptep, 0);
+ /*
+ * Set the SPTE to a nonpresent value that other
+ * threads will not overwrite. If the SPTE was
+ * already marked as removed then another thread
+ * handling a page fault could overwrite it, so
+ * set the SPTE until it is set from some other
+ * value to the removed SPTE value.
+ */
+ for (;;) {
+ old_child_spte = xchg(sptep, REMOVED_SPTE);
+ if (!is_removed_spte(old_child_spte))
+ break;
+ cpu_relax();
+ }
} else {
old_child_spte = READ_ONCE(*sptep);
- WRITE_ONCE(*sptep, 0);
+
+ /*
+ * Marking the SPTE as a removed SPTE is not
+ * strictly necessary here as the MMU lock will
+ * stop other threads from concurrently modifying
+ * this SPTE. Using the removed SPTE value keeps
+ * the two branches consistent and simplifies
+ * the function.
+ */
+ WRITE_ONCE(*sptep, REMOVED_SPTE);
}
- handle_changed_spte(kvm, kvm_mmu_page_as_id(sp),
- gfn + (i * KVM_PAGES_PER_HPAGE(level - 1)),
- old_child_spte, 0, level - 1, shared);
+ handle_changed_spte(kvm, kvm_mmu_page_as_id(sp), gfn,
+ old_child_spte, REMOVED_SPTE, level - 1,
+ shared);
}
kvm_flush_remote_tlbs_with_address(kvm, gfn,