[PATCH v5 5/9] KVM: selftests: Make kvm_create_max_vcpus tolerate ENOMEM

[Ritesh Harjani (IBM)]

Some hosts (like in case of nested guest the hypervisor L0 might have
quotas/limited resources for L1 guest) can run out of hypervisor
resources before hitting KVM_CAP_MAX_VCPUS.

This patch make use of the helper we introduced in the previous patch
(__vm_vcpu_try_add()) to tolerate such scenarios where an ENOMEM can
occur.

Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@xxxxxxxxx>
---
 .../testing/selftests/kvm/include/kvm_util.h  |  3 +++
 .../selftests/kvm/kvm_create_max_vcpus.c      | 21 +++++++++++++++----
 tools/testing/selftests/kvm/lib/kvm_util.c    |  5 +++++
 3 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index aa521b383abe..576bbebe0679 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -1064,6 +1064,9 @@ const char *exit_reason_str(unsigned int exit_reason);
 
 bool kvm_arch_needs_naturally_aligned_page_tables(void);
 
+/* True if KVM_CREATE_VM / KVM_CREATE_VCPU may return ENOMEM. */
+bool kvm_arch_vm_create_may_enomem(void);
+
 gpa_t ____vm_phy_pages_alloc(struct kvm_vm *vm, size_t nr_pages, gpa_t min_gpa,
 			     u32 memslot, bool protected, bool naturally_aligned);
 gpa_t __vm_phy_pages_alloc(struct kvm_vm *vm, size_t nr_pages,
diff --git a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
index 59ddc3757943..45a9d8b369b5 100644
--- a/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
+++ b/tools/testing/selftests/kvm/kvm_create_max_vcpus.c
@@ -20,16 +20,29 @@
 void test_vcpu_creation(int first_vcpu_id, int num_vcpus)
 {
 	struct kvm_vm *vm;
-	int i;
+	struct kvm_vcpu *vcpu;
+	int i, created = 0;
 
 	pr_info("Testing creating %d vCPUs, with IDs %d...%d.\n",
 		num_vcpus, first_vcpu_id, first_vcpu_id + num_vcpus - 1);
 
 	vm = vm_create_barebones();
 
-	for (i = first_vcpu_id; i < first_vcpu_id + num_vcpus; i++)
-		/* This asserts that the vCPU was created. */
-		__vm_vcpu_add(vm, i);
+	for (i = first_vcpu_id; i < first_vcpu_id + num_vcpus; i++) {
+		vcpu = __vm_vcpu_try_add(vm, i);
+		if (vcpu) {
+			created++;
+			continue;
+		}
+
+		TEST_ASSERT(errno == ENOMEM && kvm_arch_vm_create_may_enomem(),
+			    "KVM_CREATE_VCPU failed for id %d, errno: %d (%s)",
+			    i, errno, strerror(errno));
+		TEST_ASSERT(created > 0,
+			    "KVM_CREATE_VCPU failed with ENOMEM before creating any vCPUs");
+		pr_info("Created %d vCPUs before ENOMEM at id %d\n", created, i);
+		break;
+	}
 
 	kvm_vm_free(vm);
 }
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 7084ed90e4cc..b4d6b8167466 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -2112,6 +2112,11 @@ __weak bool kvm_arch_needs_naturally_aligned_page_tables(void)
 	return false;
 }
 
+__weak bool kvm_arch_vm_create_may_enomem(void)
+{
+	return false;
+}
+
 gpa_t __vm_phy_pages_alloc(struct kvm_vm *vm, size_t nr_pages,
 			   enum kvm_mem_region_type type, bool protected)
 {
-- 
2.39.5