KVM: selftests: Add option to run dirty_log_perf_test vCPUs in L2

Add an option to dirty_log_perf_test that configures the vCPUs to run in
L2 instead of L1. This makes it possible to benchmark the dirty logging
performance of nested virtualization, which is particularly interesting
because KVM must shadow L1's EPT/NPT tables.

For now this support only works on x86_64 CPUs with VMX. Otherwise
passing -n results in the test being skipped.

Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20220520233249.3776001-11-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 30 insertions, 5 deletions

diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
index 722df3a28791..b2ff2cee2e51 100644
--- a/tools/testing/selftests/kvm/lib/perf_test_util.c
+++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
@@ -40,7 +40,7 @@ static bool all_vcpu_threads_running;
  * Continuously write to the first 8 bytes of each page in the
  * specified region.
  */
-static void guest_code(uint32_t vcpu_id)
+void perf_test_guest_code(uint32_t vcpu_id)
 {
 	struct perf_test_args *pta = &perf_test_args;
 	struct perf_test_vcpu_args *vcpu_args = &pta->vcpu_args[vcpu_id];
@@ -108,7 +108,7 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int vcpus,
 {
 	struct perf_test_args *pta = &perf_test_args;
 	struct kvm_vm *vm;
-	uint64_t guest_num_pages;
+	uint64_t guest_num_pages, slot0_pages = DEFAULT_GUEST_PHY_PAGES;
 	uint64_t backing_src_pagesz = get_backing_src_pagesz(backing_src);
 	int i;
 
@@ -135,12 +135,19 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int vcpus,
 		    slots);
 
 	/*
+	 * If using nested, allocate extra pages for the nested page tables and
+	 * in-memory data structures.
+	 */
+	if (pta->nested)
+		slot0_pages += perf_test_nested_pages(vcpus);
+
+	/*
 	 * Pass guest_num_pages to populate the page tables for test memory.
 	 * The memory is also added to memslot 0, but that's a benign side
 	 * effect as KVM allows aliasing HVAs in meslots.
 	 */
-	vm = vm_create_with_vcpus(mode, vcpus, DEFAULT_GUEST_PHY_PAGES,
-				  guest_num_pages, 0, guest_code, NULL);
+	vm = vm_create_with_vcpus(mode, vcpus, slot0_pages, guest_num_pages, 0,
+				  perf_test_guest_code, NULL);
 
 	pta->vm = vm;
 
@@ -161,7 +168,9 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int vcpus,
 	/* Align to 1M (segment size) */
 	pta->gpa = align_down(pta->gpa, 1 << 20);
 #endif
-	pr_info("guest physical test memory offset: 0x%lx\n", pta->gpa);
+	pta->size = guest_num_pages * pta->guest_page_size;
+	pr_info("guest physical test memory: [0x%lx, 0x%lx)\n",
+		pta->gpa, pta->gpa + pta->size);
 
 	/* Add extra memory slots for testing */
 	for (i = 0; i < slots; i++) {
@@ -178,6 +187,11 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int vcpus,
 
 	perf_test_setup_vcpus(vm, vcpus, vcpu_memory_bytes, partition_vcpu_memory_access);
 
+	if (pta->nested) {
+		pr_info("Configuring vCPUs to run in L2 (nested).\n");
+		perf_test_setup_nested(vm, vcpus);
+	}
+
 	ucall_init(vm, NULL);
 
 	/* Export the shared variables to the guest. */
@@ -198,6 +212,17 @@ void perf_test_set_wr_fract(struct kvm_vm *vm, int wr_fract)
 	sync_global_to_guest(vm, perf_test_args);
 }
 
+uint64_t __weak perf_test_nested_pages(int nr_vcpus)
+{
+	return 0;
+}
+
+void __weak perf_test_setup_nested(struct kvm_vm *vm, int nr_vcpus)
+{
+	pr_info("%s() not support on this architecture, skipping.\n", __func__);
+	exit(KSFT_SKIP);
+}
+
 static void *vcpu_thread_main(void *data)
 {
 	struct vcpu_thread *vcpu = data;