Merge branch 'topic/ppc-kvm' into next

Merge one more commit from the topic branch we shared with the kvm-ppc
tree.

This brings in a fix to the code that scans for dirty pages during
migration of a VM, which was incorrectly triggering a warning.

1 files changed, 29 insertions, 6 deletions

diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
index 271f1c3d8443..954fd7a12149 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
@@ -1040,7 +1040,7 @@ static int kvm_radix_test_clear_dirty(struct kvm *kvm,
 {
 	unsigned long gfn = memslot->base_gfn + pagenum;
 	unsigned long gpa = gfn << PAGE_SHIFT;
-	pte_t *ptep;
+	pte_t *ptep, pte;
 	unsigned int shift;
 	int ret = 0;
 	unsigned long old, *rmapp;
@@ -1048,12 +1048,35 @@ static int kvm_radix_test_clear_dirty(struct kvm *kvm,
 	if (kvm->arch.secure_guest & KVMPPC_SECURE_INIT_DONE)
 		return ret;
 
-	ptep = find_kvm_secondary_pte(kvm, gpa, &shift);
-	if (ptep && pte_present(*ptep) && pte_dirty(*ptep)) {
-		ret = 1;
-		if (shift)
-			ret = 1 << (shift - PAGE_SHIFT);
+	/*
+	 * For performance reasons we don't hold kvm->mmu_lock while walking the
+	 * partition scoped table.
+	 */
+	ptep = find_kvm_secondary_pte_unlocked(kvm, gpa, &shift);
+	if (!ptep)
+		return 0;
+
+	pte = READ_ONCE(*ptep);
+	if (pte_present(pte) && pte_dirty(pte)) {
 		spin_lock(&kvm->mmu_lock);
+		/*
+		 * Recheck the pte again
+		 */
+		if (pte_val(pte) != pte_val(*ptep)) {
+			/*
+			 * We have KVM_MEM_LOG_DIRTY_PAGES enabled. Hence we can
+			 * only find PAGE_SIZE pte entries here. We can continue
+			 * to use the pte addr returned by above page table
+			 * walk.
+			 */
+			if (!pte_present(*ptep) || !pte_dirty(*ptep)) {
+				spin_unlock(&kvm->mmu_lock);
+				return 0;
+			}
+		}
+
+		ret = 1;
+		VM_BUG_ON(shift);
 		old = kvmppc_radix_update_pte(kvm, ptep, _PAGE_DIRTY, 0,
 					      gpa, shift);
 		kvmppc_radix_tlbie_page(kvm, gpa, shift, kvm->arch.lpid);