KVM: riscv: selftests: Add sstc timer test

Add a KVM selftests to validate the Sstc timer functionality.
The test was ported from arm64 arch timer test.

Signed-off-by: Haibo Xu <[e-mail]>
Reviewed-by: Andrew Jones <[e-mail]>
Signed-off-by: Anup Patel <[e-mail]>

tools/testing/selftests/kvm/Makefile

···
 TEST_GEN_PROGS_s390x += set_memory_region_test
 TEST_GEN_PROGS_s390x += kvm_binary_stats_test
 
+TEST_GEN_PROGS_riscv += arch_timer
 TEST_GEN_PROGS_riscv += demand_paging_test
 TEST_GEN_PROGS_riscv += dirty_log_test
 TEST_GEN_PROGS_riscv += get-reg-list

tools/testing/selftests/kvm/aarch64/arch_timer.c

···
 	vm_init_descriptor_tables(vm);
 	vm_install_exception_handler(vm, VECTOR_IRQ_CURRENT, guest_irq_handler);
 
-	if (!test_args.offset.reserved) {
-		if (kvm_has_cap(KVM_CAP_COUNTER_OFFSET))
-			vm_ioctl(vm, KVM_ARM_SET_COUNTER_OFFSET, &test_args.offset);
-		else
+	if (!test_args.reserved) {
+		if (kvm_has_cap(KVM_CAP_COUNTER_OFFSET)) {
+			struct kvm_arm_counter_offset offset = {
+				.counter_offset = test_args.counter_offset,
+				.reserved = 0,
+			};
+			vm_ioctl(vm, KVM_ARM_SET_COUNTER_OFFSET, &offset);
+		} else
 			TEST_FAIL("no support for global offset");
 	}
 

tools/testing/selftests/kvm/arch_timer.c

···
 	.timer_period_ms = TIMER_TEST_PERIOD_MS_DEF,
 	.migration_freq_ms = TIMER_TEST_MIGRATION_FREQ_MS,
 	.timer_err_margin_us = TIMER_TEST_ERR_MARGIN_US,
-	.offset = { .reserved = 1 },
+	.reserved = 1,
 };
 
 struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
···
 	default:
 		TEST_FAIL("Unexpected guest exit");
 	}
+
+	pr_info("PASS(vCPU-%d).\n", vcpu_idx);
 
 	return NULL;
 }
···
 		TIMER_TEST_PERIOD_MS_DEF);
 	pr_info("\t-m: Frequency (in ms) of vCPUs to migrate to different pCPU. 0 to turn off (default: %u)\n",
 		TIMER_TEST_MIGRATION_FREQ_MS);
-	pr_info("\t-o: Counter offset (in counter cycles, default: 0)\n");
+	pr_info("\t-o: Counter offset (in counter cycles, default: 0) [aarch64-only]\n");
 	pr_info("\t-e: Interrupt arrival error margin (in us) of the guest timer (default: %u)\n",
 		TIMER_TEST_ERR_MARGIN_US);
 	pr_info("\t-h: print this help screen\n");
···
 			test_args.timer_err_margin_us = atoi_non_negative("Error Margin", optarg);
 			break;
 		case 'o':
-			test_args.offset.counter_offset = strtol(optarg, NULL, 0);
-			test_args.offset.reserved = 0;
+			test_args.counter_offset = strtol(optarg, NULL, 0);
+			test_args.reserved = 0;
 			break;
 		case 'h':
 		default:

tools/testing/selftests/kvm/include/riscv/arch_timer.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * RISC-V Arch Timer(sstc) specific interface
+ *
+ * Copyright (c) 2024 Intel Corporation
+ */
+
+#ifndef SELFTEST_KVM_ARCH_TIMER_H
+#define SELFTEST_KVM_ARCH_TIMER_H
+
+#include <asm/csr.h>
+#include <asm/vdso/processor.h>
+
+static unsigned long timer_freq;
+
+#define msec_to_cycles(msec)	\
+	((timer_freq) * (uint64_t)(msec) / 1000)
+
+#define usec_to_cycles(usec)	\
+	((timer_freq) * (uint64_t)(usec) / 1000000)
+
+#define cycles_to_usec(cycles) \
+	((uint64_t)(cycles) * 1000000 / (timer_freq))
+
+static inline uint64_t timer_get_cycles(void)
+{
+	return csr_read(CSR_TIME);
+}
+
+static inline void timer_set_cmp(uint64_t cval)
+{
+	csr_write(CSR_STIMECMP, cval);
+}
+
+static inline uint64_t timer_get_cmp(void)
+{
+	return csr_read(CSR_STIMECMP);
+}
+
+static inline void timer_irq_enable(void)
+{
+	csr_set(CSR_SIE, IE_TIE);
+}
+
+static inline void timer_irq_disable(void)
+{
+	csr_clear(CSR_SIE, IE_TIE);
+}
+
+static inline void timer_set_next_cmp_ms(uint32_t msec)
+{
+	uint64_t now_ct = timer_get_cycles();
+	uint64_t next_ct = now_ct + msec_to_cycles(msec);
+
+	timer_set_cmp(next_ct);
+}
+
+static inline void __delay(uint64_t cycles)
+{
+	uint64_t start = timer_get_cycles();
+
+	while ((timer_get_cycles() - start) < cycles)
+		cpu_relax();
+}
+
+static inline void udelay(unsigned long usec)
+{
+	__delay(usec_to_cycles(usec));
+}
+
+#endif /* SELFTEST_KVM_ARCH_TIMER_H */

tools/testing/selftests/kvm/include/riscv/processor.h

···
 
 bool guest_sbi_probe_extension(int extid, long *out_val);
 
+static inline void local_irq_enable(void)
+{
+	csr_set(CSR_SSTATUS, SR_SIE);
+}
+
+static inline void local_irq_disable(void)
+{
+	csr_clear(CSR_SSTATUS, SR_SIE);
+}
+
 #endif /* SELFTEST_KVM_PROCESSOR_H */

tools/testing/selftests/kvm/include/timer_test.h

···
 	uint32_t timer_period_ms;
 	uint32_t migration_freq_ms;
 	uint32_t timer_err_margin_us;
-	/* TODO: Change arm specific type to a common one */
-	struct kvm_arm_counter_offset offset;
+	/* Members of struct kvm_arm_counter_offset */
+	uint64_t counter_offset;
+	uint64_t reserved;
 };
 
 /* Shared variables between host and guest */

tools/testing/selftests/kvm/riscv/arch_timer.c

···
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * arch_timer.c - Tests the riscv64 sstc timer IRQ functionality
+ *
+ * The test validates the sstc timer IRQs using vstimecmp registers.
+ * It's ported from the aarch64 arch_timer test.
+ *
+ * Copyright (c) 2024, Intel Corporation.
+ */
+
+#define _GNU_SOURCE
+
+#include "arch_timer.h"
+#include "kvm_util.h"
+#include "processor.h"
+#include "timer_test.h"
+
+static int timer_irq = IRQ_S_TIMER;
+
+static void guest_irq_handler(struct ex_regs *regs)
+{
+	uint64_t xcnt, xcnt_diff_us, cmp;
+	unsigned int intid = regs->cause & ~CAUSE_IRQ_FLAG;
+	uint32_t cpu = guest_get_vcpuid();
+	struct test_vcpu_shared_data *shared_data = &vcpu_shared_data[cpu];
+
+	timer_irq_disable();
+
+	xcnt = timer_get_cycles();
+	cmp = timer_get_cmp();
+	xcnt_diff_us = cycles_to_usec(xcnt - shared_data->xcnt);
+
+	/* Make sure we are dealing with the correct timer IRQ */
+	GUEST_ASSERT_EQ(intid, timer_irq);
+
+	__GUEST_ASSERT(xcnt >= cmp,
+			"xcnt = 0x%"PRIx64", cmp = 0x%"PRIx64", xcnt_diff_us = 0x%" PRIx64,
+			xcnt, cmp, xcnt_diff_us);
+
+	WRITE_ONCE(shared_data->nr_iter, shared_data->nr_iter + 1);
+}
+
+static void guest_run(struct test_vcpu_shared_data *shared_data)
+{
+	uint32_t irq_iter, config_iter;
+
+	shared_data->nr_iter = 0;
+	shared_data->guest_stage = 0;
+
+	for (config_iter = 0; config_iter < test_args.nr_iter; config_iter++) {
+		/* Setup the next interrupt */
+		timer_set_next_cmp_ms(test_args.timer_period_ms);
+		shared_data->xcnt = timer_get_cycles();
+		timer_irq_enable();
+
+		/* Setup a timeout for the interrupt to arrive */
+		udelay(msecs_to_usecs(test_args.timer_period_ms) +
+			test_args.timer_err_margin_us);
+
+		irq_iter = READ_ONCE(shared_data->nr_iter);
+		__GUEST_ASSERT(config_iter + 1 == irq_iter,
+				"config_iter + 1 = 0x%x, irq_iter = 0x%x.\n"
+				"  Guest timer interrupt was not trigged within the specified\n"
+				"  interval, try to increase the error margin by [-e] option.\n",
+				config_iter + 1, irq_iter);
+	}
+}
+
+static void guest_code(void)
+{
+	uint32_t cpu = guest_get_vcpuid();
+	struct test_vcpu_shared_data *shared_data = &vcpu_shared_data[cpu];
+
+	timer_irq_disable();
+	local_irq_enable();
+
+	guest_run(shared_data);
+
+	GUEST_DONE();
+}
+
+struct kvm_vm *test_vm_create(void)
+{
+	struct kvm_vm *vm;
+	int nr_vcpus = test_args.nr_vcpus;
+
+	vm = vm_create_with_vcpus(nr_vcpus, guest_code, vcpus);
+	__TEST_REQUIRE(__vcpu_has_ext(vcpus[0], RISCV_ISA_EXT_REG(KVM_RISCV_ISA_EXT_SSTC)),
+				   "SSTC not available, skipping test\n");
+
+	vm_init_vector_tables(vm);
+	vm_install_interrupt_handler(vm, guest_irq_handler);
+
+	for (int i = 0; i < nr_vcpus; i++)
+		vcpu_init_vector_tables(vcpus[i]);
+
+	/* Initialize guest timer frequency. */
+	vcpu_get_reg(vcpus[0], RISCV_TIMER_REG(frequency), &timer_freq);
+	sync_global_to_guest(vm, timer_freq);
+	pr_debug("timer_freq: %lu\n", timer_freq);
+
+	/* Make all the test's cmdline args visible to the guest */
+	sync_global_to_guest(vm, test_args);
+
+	return vm;
+}
+
+void test_vm_cleanup(struct kvm_vm *vm)
+{
+	kvm_vm_free(vm);
+}