[RFC PATCH v5 6/6] KVM: selftests: Add tests for VM and vCPU cap KVM_CAP_X86_DISABLE_EXITS

Kechen Lu
2023-01-13T22:03:10Z

Add selftests for KVM cap KVM_CAP_X86_DISABLE_EXITS overriding flags
in VM and vCPU scope both works as expected.

Suggested-by: Chao Gao <chao.gao@intel.com>
Suggested-by: Shaoqin Huang <shaoqin.huang@intel.com>
Signed-off-by: Kechen Lu <kechenl@nvidia.com>
---
tools/testing/selftests/kvm/Makefile | 1 +
.../selftests/kvm/x86_64/disable_exits_test.c | 457 ++++++++++++++++++
2 files changed, 458 insertions(+)
create mode 100644 tools/testing/selftests/kvm/x86_64/disable_exits_test.c

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 1750f91dd936..eeeba35e2536 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -114,6 +114,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/sev_migrate_tests
TEST_GEN_PROGS_x86_64 += x86_64/amx_test
TEST_GEN_PROGS_x86_64 += x86_64/max_vcpuid_cap_test
TEST_GEN_PROGS_x86_64 += x86_64/triple_fault_event_test
+TEST_GEN_PROGS_x86_64 += x86_64/disable_exits_test
TEST_GEN_PROGS_x86_64 += access_tracking_perf_test
TEST_GEN_PROGS_x86_64 += demand_paging_test
TEST_GEN_PROGS_x86_64 += dirty_log_test
diff --git a/tools/testing/selftests/kvm/x86_64/disable_exits_test.c b/tools/testing/selftests/kvm/x86_64/disable_exits_test.c
new file mode 100644
index 000000000000..dceba3bcef5f
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/disable_exits_test.c
@@ -0,0 +1,457 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Test per-VM and per-vCPU disable exits cap
+ * 1) Per-VM scope
+ * 2) Per-vCPU scope
+ *
+ */
+
+#define _GNU_SOURCE /* for program_invocation_short_name */
+#include <pthread.h>
+#include <inttypes.h>
+#include <string.h>
+#include <time.h>
+#include <sys/ioctl.h>
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "svm_util.h"
+#include "vmx.h"
+#include "processor.h"
+#include "asm/kvm.h"
+#include "linux/kvm.h"
+
+/* Arbitary chosen IPI vector value from sender to halter vCPU */
+#define IPI_VECTOR 0xa5
+/* Number of HLTs halter vCPU thread executes */
+#define COUNT_HLT_EXITS 10
+
+struct guest_stats {
+ uint32_t halter_apic_id;
+ volatile uint64_t hlt_count;
+ volatile uint64_t wake_count;
+};
+
+static u64 read_vcpu_stats_halt_exits(struct kvm_vcpu *vcpu)
+{
+ int i;
+ struct kvm_stats_header header;
+ u64 *stats_data;
+ u64 ret = 0;
+ struct kvm_stats_desc *stats_desc;
+ struct kvm_stats_desc *pdesc;
+ int stats_fd = vcpu_get_stats_fd(vcpu);
+
+ read_stats_header(stats_fd, &header);
+ if (header.num_desc == 0) {
+ fprintf(stderr,
+ "Cannot read halt exits since no KVM stats defined\n");
+ return ret;
+ }
+
+ stats_desc = read_stats_descriptors(stats_fd, &header);
+ for (i = 0; i < header.num_desc; ++i) {
+ pdesc = get_stats_descriptor(stats_desc, i, &header);
+ if (!strncmp(pdesc->name, "halt_exits", 10)) {
+ stats_data = malloc(pdesc->size * sizeof(*stats_data));
+ read_stat_data(stats_fd, &header, pdesc, stats_data,
+ pdesc->size);
+ ret = *stats_data;
+ free(stats_data);
+ break;
+ }
+ }
+ free(stats_desc);
+ return ret;
+}
+
+/* HLT multiple times in one vCPU */
+static void halter_guest_code(struct guest_stats *data)
+{
+ xapic_enable();
+ data->halter_apic_id = GET_APIC_ID_FIELD(xapic_read_reg(APIC_ID));
+
+ for (;;) {
+ data->hlt_count++;
+ asm volatile("sti; hlt; cli");
+ data->wake_count++;
+ }
+}
+
+static void halter_waiting_guest_code(struct guest_stats *data)
+{
+ uint64_t tsc_start = rdtsc();
+
+ xapic_enable();
+ data->halter_apic_id = GET_APIC_ID_FIELD(xapic_read_reg(APIC_ID));
+
+ for (;;) {
+ data->hlt_count++;
+ asm volatile("sti; hlt; cli");
+ data->wake_count++;
+ /* Wait for ~0.5sec for each HLT execution */
+ tsc_start = rdtsc();
+ while (rdtsc() - tsc_start < 2000000000);
+ }
+}
+
+/* Runs on halter vCPU when IPI arrives */
+static void guest_ipi_handler(struct ex_regs *regs)
+{
+ xapic_write_reg(APIC_EOI, 11);
+}
+
+/* Sender vCPU waits for ~1sec to assume HLT executed */
+static void sender_wait_loop(struct guest_stats *data, uint64_t old_hlt_count,
+ uint64_t old_wake_count)
+{
+ uint64_t tsc_start = rdtsc();
+ while (rdtsc() - tsc_start < 4000000000);
+ GUEST_ASSERT((data->wake_count != old_wake_count) &&
+ (data->hlt_count != old_hlt_count));
+}
+
+/* Sender vCPU loops sending IPI to halter vCPU every ~1sec */
+static void sender_guest_code(struct guest_stats *data)
+{
+ uint32_t icr_val;
+ uint32_t icr2_val;
+ uint64_t old_hlt_count = 0;
+ uint64_t old_wake_count = 0;
+
+ xapic_enable();
+ /* Init interrupt command register for sending IPIs */
+ icr_val = (APIC_DEST_PHYSICAL | APIC_DM_FIXED | IPI_VECTOR);
+ icr2_val = SET_APIC_DEST_FIELD(data->halter_apic_id);
+
+ for (;;) {
+ /*
+ * Send IPI to halted vCPU
+ * First IPI sends here as already waited before sender vCPU
+ * thread creation
+ */
+ xapic_write_reg(APIC_ICR2, icr2_val);
+ xapic_write_reg(APIC_ICR, icr_val);
+ sender_wait_loop(data, old_hlt_count, old_wake_count);
+ GUEST_ASSERT((data->wake_count != old_wake_count) &&
+ (data->hlt_count != old_hlt_count));
+ old_wake_count = data->wake_count;
+ old_hlt_count = data->hlt_count;
+ }
+}
+
+static void *vcpu_thread(void *arg)
+{
+ struct kvm_vcpu *vcpu = (struct kvm_vcpu *)arg;
+ int old;
+ int r;
+
+ r = pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, &old);
+ TEST_ASSERT(r == 0,
+ "pthread_setcanceltype failed on vcpu_id=%u with errno=%d",
+ vcpu->id, r);
+ fprintf(stderr, "vCPU thread running vCPU %u\n", vcpu->id);
+ vcpu_run(vcpu);
+ return NULL;
+}
+
+static void cancel_join_vcpu_thread(pthread_t thread, struct kvm_vcpu *vcpu)
+{
+ void *retval;
+ int r;
+
+ r = pthread_cancel(thread);
+ TEST_ASSERT(r == 0,
+ "pthread_cancel on vcpu_id=%d failed with errno=%d",
+ vcpu->id, r);
+
+ r = pthread_join(thread, &retval);
+ TEST_ASSERT(r == 0,
+ "pthread_join on vcpu_id=%d failed with errno=%d",
+ vcpu->id, r);
+}
+
+/*
+ * Test case 1:
+ * Normal VM running with one vCPU keeps executing HLTs,
+ * another vCPU sending IPIs to wake it up, should expect
+ * all HLTs exiting to host
+ */
+static void test_vm_without_disable_exits_cap(void)
+{
+ int r;
+ int wait_secs;
+ const int first_halter_wait = 10;
+ uint64_t kvm_halt_exits;
+ struct kvm_vm *vm;
+ struct kvm_vcpu *halter_vcpu;
+ struct kvm_vcpu *sender_vcpu;
+ struct guest_stats *data;
+ vm_vaddr_t guest_stats_page_vaddr;
+ pthread_t threads[2];
+
+ /* Create VM */
+ vm = vm_create(2);
+
+ /* Add vCPU with loops halting */
+ halter_vcpu = vm_vcpu_add(vm, 0, halter_guest_code);
+
+ vm_init_descriptor_tables(vm);
+ vcpu_init_descriptor_tables(halter_vcpu);
+ vm_install_exception_handler(vm, IPI_VECTOR, guest_ipi_handler);
+ virt_pg_map(vm, APIC_DEFAULT_GPA, APIC_DEFAULT_GPA);
+
+ /* Add vCPU with IPIs waking up halter vCPU */
+ sender_vcpu = vm_vcpu_add(vm, 1, sender_guest_code);
+
+ guest_stats_page_vaddr = vm_vaddr_alloc_page(vm);
+ data = addr_gva2hva(vm, guest_stats_page_vaddr);
+ memset(data, 0, sizeof(*data));
+
+ vcpu_args_set(halter_vcpu, 1, guest_stats_page_vaddr);
+ vcpu_args_set(sender_vcpu, 1, guest_stats_page_vaddr);
+
+ /* Start halter vCPU thread and wait for it to execute first HLT. */
+ r = pthread_create(&threads[0], NULL, vcpu_thread, halter_vcpu);
+ TEST_ASSERT(r == 0,
+ "pthread_create halter failed errno=%d", errno);
+ fprintf(stderr, "Halter vCPU thread started\n");
+
+ wait_secs = 0;
+ while ((wait_secs < first_halter_wait) && !data->hlt_count) {
+ sleep(1);
+ wait_secs++;
+ }
+ TEST_ASSERT(data->hlt_count,
+ "Halter vCPU did not execute first HLT within %d seconds",
+ first_halter_wait);
+ fprintf(stderr,
+ "Halter vCPU thread reported its first HLT executed "
+ "after %d seconds.\n",
+ wait_secs);
+
+ /*
+ * After guest halter vCPU executed first HLT, start the sender
+ * vCPU thread to wakeup halter vCPU
+ */
+ r = pthread_create(&threads[1], NULL, vcpu_thread, sender_vcpu);
+ TEST_ASSERT(r == 0, "pthread_create sender failed errno=%d", errno);
+
+ while (data->hlt_count < COUNT_HLT_EXITS);
+
+ cancel_join_vcpu_thread(threads[0], halter_vcpu);
+ cancel_join_vcpu_thread(threads[1], sender_vcpu);
+
+ kvm_halt_exits = read_vcpu_stats_halt_exits(halter_vcpu);
+ TEST_ASSERT(kvm_halt_exits == data->hlt_count,
+ "Halter vCPU had unmatched %lu halt exits - %lu HLTs "
+ "executed, when not disabling VM halt exits\n",
+ kvm_halt_exits, data->hlt_count);
+ fprintf(stderr, "Halter vCPU had %lu halt exits\n",
+ kvm_halt_exits);
+ fprintf(stderr, "Guest records %lu HLTs executed, "
+ "waked %lu times\n",
+ data->hlt_count, data->wake_count);
+
+ kvm_vm_free(vm);
+}
+
+/*
+ * Test case 2:
+ * VM scoped exits disabling, HLT instructions
+ * stay inside guest without exits
+ */
+static void test_vm_disable_exits_cap(void)
+{
+ int r;
+ uint64_t kvm_halt_exits;
+ struct kvm_vm *vm;
+ struct kvm_vcpu *halter_vcpu;
+ struct guest_stats *data;
+ vm_vaddr_t guest_stats_page_vaddr;
+ pthread_t halter_thread;
+
+ /* Create VM */
+ vm = vm_create(1);
+
+ /*
+ * Before adding any vCPUs, enable the KVM_X86_DISABLE_EXITS cap
+ * with flag KVM_X86_DISABLE_EXITS_HLT
+ */
+ vm_enable_cap(vm, KVM_CAP_X86_DISABLE_EXITS,
+ KVM_X86_DISABLE_EXITS_HLT);
+
+ /* Add vCPU with loops halting */
+ halter_vcpu = vm_vcpu_add(vm, 0, halter_waiting_guest_code);
+
+ vm_init_descriptor_tables(vm);
+ vcpu_init_descriptor_tables(halter_vcpu);
+ vm_install_exception_handler(vm, IPI_VECTOR, guest_ipi_handler);
+ virt_pg_map(vm, APIC_DEFAULT_GPA, APIC_DEFAULT_GPA);
+
+ guest_stats_page_vaddr = vm_vaddr_alloc_page(vm);
+ data = addr_gva2hva(vm, guest_stats_page_vaddr);
+ memset(data, 0, sizeof(*data));
+ vcpu_args_set(halter_vcpu, 1, guest_stats_page_vaddr);
+
+ /* Start halter vCPU thread and execute HLTs immediately */
+ r = pthread_create(&halter_thread, NULL, vcpu_thread, halter_vcpu);
+ TEST_ASSERT(r == 0,
+ "pthread_create halter failed errno=%d", errno);
+ fprintf(stderr, "Halter vCPU thread started\n");
+
+ while (data->hlt_count < COUNT_HLT_EXITS);
+
+ cancel_join_vcpu_thread(halter_thread, halter_vcpu);
+
+ kvm_halt_exits = read_vcpu_stats_halt_exits(halter_vcpu);
+ TEST_ASSERT(kvm_halt_exits == 0,
+ "Halter vCPU had unexpected halt exits occuring after "
+ "disabling VM-scoped halt exits cap\n");
+ fprintf(stderr, "Halter vCPU had %lu HLT exits\n",
+ kvm_halt_exits);
+ fprintf(stderr, "Guest records %lu HLTs executed\n",
+ data->hlt_count);
+
+ kvm_vm_free(vm);
+}
+
+/*
+ * Test case 3:
+ * VM overrides exits disable flags after vCPU created,
+ * which is not allowed
+ */
+static void test_vm_disable_exits_cap_with_vcpu_created(void)
+{
+ int r;
+ struct kvm_vm *vm;
+ struct kvm_enable_cap cap = {
+ .cap = KVM_CAP_X86_DISABLE_EXITS,
+ .args[0] = KVM_X86_DISABLE_EXITS_HLT | KVM_X86_DISABLE_EXITS_OVERRIDE,
+ };
+
+ /* Create VM */
+ vm = vm_create(1);
+ /* Add vCPU with loops halting */
+ vm_vcpu_add(vm, 0, halter_waiting_guest_code);
+
+ /*
+ * After creating vCPU, the current VM-scoped ABI should
+ * discard the cap enable of KVM_CAP_X86_DISABLE_EXITS
+ * and return non-zero. Since vm_enabled_cap() not able
+ * to assert the return value, so use the __vm_ioctl()
+ */
+ r = __vm_ioctl(vm, KVM_ENABLE_CAP, &cap);
+
+ TEST_ASSERT(r != 0,
+ "Setting VM-scoped KVM_CAP_X86_DISABLE_EXITS after "
+ "vCPUs created is not allowed, but it succeeds here\n");
+}
+
+/*
+ * Test case 4:
+ * vCPU scoped halt exits disabling and enabling tests,
+ * verify overides are working after vCPU created
+ */
+static void test_vcpu_toggling_disable_exits_cap(void)
+{
+ int r;
+ uint64_t kvm_halt_exits;
+ struct kvm_vm *vm;
+ struct kvm_vcpu *halter_vcpu;
+ struct kvm_vcpu *sender_vcpu;
+ struct guest_stats *data;
+ vm_vaddr_t guest_stats_page_vaddr;
+ pthread_t threads[2];
+
+ /* Create VM */
+ vm = vm_create(2);
+
+ /* Add vCPU with loops halting */
+ halter_vcpu = vm_vcpu_add(vm, 0, halter_waiting_guest_code);
+ /* Set KVM_CAP_X86_DISABLE_EXITS_HLT for halter vCPU */
+ vcpu_enable_cap(halter_vcpu, KVM_CAP_X86_DISABLE_EXITS,
+ KVM_X86_DISABLE_EXITS_HLT | KVM_X86_DISABLE_EXITS_OVERRIDE);
+
+ vm_init_descriptor_tables(vm);
+ vcpu_init_descriptor_tables(halter_vcpu);
+ vm_install_exception_handler(vm, IPI_VECTOR, guest_ipi_handler);
+
+ virt_pg_map(vm, APIC_DEFAULT_GPA, APIC_DEFAULT_GPA);
+
+ /* Add vCPU with IPIs waking up halter vCPU */
+ sender_vcpu = vm_vcpu_add(vm, 1, sender_guest_code);
+
+ guest_stats_page_vaddr = vm_vaddr_alloc_page(vm);
+ data = addr_gva2hva(vm, guest_stats_page_vaddr);
+ memset(data, 0, sizeof(*data));
+
+ vcpu_args_set(halter_vcpu, 1, guest_stats_page_vaddr);
+ vcpu_args_set(sender_vcpu, 1, guest_stats_page_vaddr);
+
+ r = pthread_create(&threads[0], NULL, vcpu_thread, halter_vcpu);
+ TEST_ASSERT(r == 0,
+ "pthread_create halter failed errno=%d", errno);
+ fprintf(stderr, "Halter vCPU thread started with halt exits"
+ "disabled\n");
+
+ /*
+ * For the first phase of the running, halt exits
+ * are disabled, halter vCPU executes HLT instruction
+ * but never exits to host
+ */
+ while (data->hlt_count < (COUNT_HLT_EXITS / 2));
+
+ cancel_join_vcpu_thread(threads[0], halter_vcpu);
+ /*
+ * Override and clean KVM_CAP_X86_DISABLE_EXITS flags
+ * for halter vCPU. Expect to see halt exits occurs then.
+ */
+ vcpu_enable_cap(halter_vcpu, KVM_CAP_X86_DISABLE_EXITS,
+ KVM_X86_DISABLE_EXITS_OVERRIDE);
+
+ r = pthread_create(&threads[0], NULL, vcpu_thread, halter_vcpu);
+ TEST_ASSERT(r == 0,
+ "pthread_create halter failed errno=%d", errno);
+ fprintf(stderr, "Halter vCPU thread restarted and cleared "
+ "halt exits flag\n");
+
+ sleep(1);
+ /*
+ * Second phase of the test, after guest halter vCPU
+ * reenabled halt exits, start the sender
+ * vCPU thread to wakeup halter vCPU
+ */
+ r = pthread_create(&threads[1], NULL, vcpu_thread, sender_vcpu);
+ TEST_ASSERT(r == 0, "pthread_create sender failed errno=%d", errno);
+
+ while (data->hlt_count < COUNT_HLT_EXITS);
+
+ cancel_join_vcpu_thread(threads[0], halter_vcpu);
+ cancel_join_vcpu_thread(threads[1], sender_vcpu);
+
+ kvm_halt_exits = read_vcpu_stats_halt_exits(halter_vcpu);
+ TEST_ASSERT(kvm_halt_exits == (COUNT_HLT_EXITS / 2),
+ "Halter vCPU had unexpected %lu halt exits, "
+ "there should be %d halt exits while "
+ "not disabling VM halt exits\n",
+ kvm_halt_exits, COUNT_HLT_EXITS / 2);
+ fprintf(stderr, "Halter vCPU had %lu halt exits\n",
+ kvm_halt_exits);
+ fprintf(stderr, "Guest records %lu HLTs executed, "
+ "waked %lu times\n",
+ data->hlt_count, data->wake_count);
+
+ kvm_vm_free(vm);
+}
+
+int main(int argc, char *argv[])
+{
+ fprintf(stderr, "VM-scoped tests start\n");
+ test_vm_without_disable_exits_cap();
+ test_vm_disable_exits_cap();
+ test_vm_disable_exits_cap_with_vcpu_created();
+ fprintf(stderr, "vCPU-scoped test starts\n");
+ test_vcpu_toggling_disable_exits_cap();
+ return 0;
+}
--
2.34.1