KVM: PPC: Book3S HV: Fix bug causing loss of page dirty state

This fixes a bug where adding a new guest HPT entry via the H_ENTER hcall would lose the "changed" bit in the reverse map information for the guest physical page being mapped. The result was that the KVM_GET_DIRTY_LOG could return a zero bit for the page even though the page had been modified by the guest. This fixes it by only modifying the index and present bits in the reverse map entry, thus preserving the reference and change bits. We were also unnecessarily setting the reference bit, and this fixes that too. Signed-off-by: Paul Mackerras <[email protected]> Signed-off-by: Alexander Graf <[email protected]>
progmanos · Dec 6, 2012 · 4879f24 · 4879f24
1 parent 7ed661b
commit 4879f24
Showing 1 changed file with 3 additions and 3 deletions.
diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -59,10 +59,10 @@ void kvmppc_add_revmap_chain(struct kvm *kvm, struct revmap_entry *rev,
 		head->back = pte_index;
 	} else {
 		rev->forw = rev->back = pte_index;
-		i = pte_index;
+		*rmap = (*rmap & ~KVMPPC_RMAP_INDEX) |
+			pte_index | KVMPPC_RMAP_PRESENT;
 	}
-	smp_wmb();
-	*rmap = i | KVMPPC_RMAP_REFERENCED | KVMPPC_RMAP_PRESENT; /* unlock */
+	unlock_rmap(rmap);
 }
 EXPORT_SYMBOL_GPL(kvmppc_add_revmap_chain);