[PATCH 3/3] KVM: arm64: selftests: Add a test case for KVM_GUESTDBG_SINGLESTEP

Reiji Watanabe
2022-09-09T04:47:19Z

Add a test case for KVM_GUESTDBG_SINGLESTEP to the debug-exceptions test.
The test enables single-step execution from userspace, and check if the
exit to userspace occurs for each instruction that is stepped.
Set the default number of the test iterations to a number of iterations
sufficient to always reproduce the problem that the previous patch fixes
on an Ampere Altra machine.

Signed-off-by: Reiji Watanabe <reijiw@google.com>
---
.../selftests/kvm/aarch64/debug-exceptions.c | 131 ++++++++++++++++++
1 file changed, 131 insertions(+)

diff --git a/tools/testing/selftests/kvm/aarch64/debug-exceptions.c b/tools/testing/selftests/kvm/aarch64/debug-exceptions.c
index e6e83b895fd5..947bd201435c 100644
--- a/tools/testing/selftests/kvm/aarch64/debug-exceptions.c
+++ b/tools/testing/selftests/kvm/aarch64/debug-exceptions.c
@@ -22,6 +22,7 @@
#define SPSR_SS (1 << 21)

extern unsigned char sw_bp, sw_bp2, hw_bp, hw_bp2, bp_svc, bp_brk, hw_wp, ss_start;
+extern unsigned char iter_ss_begin, iter_ss_end;
static volatile uint64_t sw_bp_addr, hw_bp_addr;
static volatile uint64_t wp_addr, wp_data_addr;
static volatile uint64_t svc_addr;
@@ -238,6 +239,46 @@ static void guest_svc_handler(struct ex_regs *regs)
svc_addr = regs->pc;
}

+enum single_step_op {
+ SINGLE_STEP_ENABLE = 0,
+ SINGLE_STEP_DISABLE = 1,
+};
+
+static void guest_code_ss(int test_cnt)
+{
+ uint64_t i;
+ uint64_t bvr, wvr, w_bvr, w_wvr;
+
+ for (i = 0; i < test_cnt; i++) {
+ /* Bits [1:0] of dbg{b,w}vr are RES0 */
+ w_bvr = i << 2;
+ w_wvr = i << 2;
+
+ /* Enable Single Step execution */
+ GUEST_SYNC(SINGLE_STEP_ENABLE);
+
+ /*
+ * The userspace will veriry that the pc is as expected during
+ * single step execution between iter_ss_begin and iter_ss_end.
+ */
+ asm volatile("iter_ss_begin:nop\n");
+
+ write_sysreg(w_bvr, dbgbvr0_el1);
+ write_sysreg(w_wvr, dbgwvr0_el1);
+ bvr = read_sysreg(dbgbvr0_el1);
+ wvr = read_sysreg(dbgwvr0_el1);
+
+ asm volatile("iter_ss_end:\n");
+
+ /* Disable Single Step execution */
+ GUEST_SYNC(SINGLE_STEP_DISABLE);
+
+ GUEST_ASSERT(bvr == w_bvr);
+ GUEST_ASSERT(wvr == w_wvr);
+ }
+ GUEST_DONE();
+}
+
static int debug_version(struct kvm_vcpu *vcpu)
{
uint64_t id_aa64dfr0;
@@ -293,16 +334,106 @@ static void test_guest_debug_exceptions(void)
kvm_vm_free(vm);
}

+void test_single_step_from_userspace(int test_cnt)
+{
+ struct kvm_vcpu *vcpu;
+ struct kvm_vm *vm;
+ struct ucall uc;
+ struct kvm_run *run;
+ uint64_t pc, cmd;
+ uint64_t test_pc = 0;
+ bool ss_enable = false;
+ struct kvm_guest_debug debug = {};
+
+ vm = vm_create_with_one_vcpu(&vcpu, guest_code_ss);
+ ucall_init(vm, NULL);
+ run = vcpu->run;
+ vcpu_args_set(vcpu, 1, test_cnt);
+
+ while (1) {
+ vcpu_run(vcpu);
+ if (run->exit_reason != KVM_EXIT_DEBUG) {
+ cmd = get_ucall(vcpu, &uc);
+ if (cmd == UCALL_ABORT) {
+ REPORT_GUEST_ASSERT(uc);
+ /* NOT REACHED */
+ } else if (cmd == UCALL_DONE) {
+ break;
+ }
+
+ TEST_ASSERT(cmd == UCALL_SYNC,
+ "Unexpected ucall cmd 0x%lx", cmd);
+
+ if (uc.args[1] == SINGLE_STEP_ENABLE) {
+ debug.control = KVM_GUESTDBG_ENABLE |
+ KVM_GUESTDBG_SINGLESTEP;
+ ss_enable = true;
+ } else {
+ debug.control = SINGLE_STEP_DISABLE;
+ ss_enable = false;
+ }
+
+ vcpu_guest_debug_set(vcpu, &debug);
+ continue;
+ }
+
+ TEST_ASSERT(ss_enable, "Unexpected KVM_EXIT_DEBUG");
+
+ /* Check if the current pc is expected. */
+ vcpu_get_reg(vcpu, ARM64_CORE_REG(regs.pc), &pc);
+ TEST_ASSERT(!test_pc || pc == test_pc,
+ "Unexpected pc 0x%lx (expected 0x%lx)",
+ pc, test_pc);
+
+ /*
+ * If the current pc is between iter_ss_bgin and
+ * iter_ss_end, the pc for the next KVM_EXIT_DEBUG should
+ * be the current pc + 4.
+ */
+ if ((pc >= (uint64_t)&iter_ss_begin) &&
+ (pc < (uint64_t)&iter_ss_end))
+ test_pc = pc + 4;
+ else
+ test_pc = 0;
+ }
+
+ kvm_vm_free(vm);
+}
+
+static void help(char *name)
+{
+ puts("");
+ printf("Usage: %s [-h] [-i iterations of the single step test]\n", name);
+ puts("");
+ exit(0);
+}
+
int main(int argc, char *argv[])
{
struct kvm_vcpu *vcpu;
struct kvm_vm *vm;
+ int opt;
+ int ss_iteration = 10000;

vm = vm_create_with_one_vcpu(&vcpu, guest_code);
__TEST_REQUIRE(debug_version(vcpu) >= 6,
"Armv8 debug architecture not supported.");
kvm_vm_free(vm);
+
+ while ((opt = getopt(argc, argv, "i:")) != -1) {
+ switch (opt) {
+ case 'i':
+ ss_iteration = atoi(optarg);
+ break;
+ case 'h':
+ default:
+ help(argv[0]);
+ break;
+ }
+ }
+
test_guest_debug_exceptions();
+ test_single_step_from_userspace(ss_iteration);

return 0;
}
--
2.37.2.789.g6183377224-goog