Re: [PATCH v2 10/10] KVM: arm64: selftests: Add arch_timer test

[Ricardo Koller <ricarkol@google.com>]

On Wed, Aug 18, 2021 at 06:43:11PM +0000, Raghavendra Rao Ananta wrote:
> Add a KVM selftest to validate the arch_timer functionality.
> Primarily, the test sets up periodic timer interrupts and
> validates the basic architectural expectations upon its receipt.
> 
> The test provides command-line options to configure the period
> of the timer, number of iterations, and number of vCPUs.
> 
> Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
> ---
>  tools/testing/selftests/kvm/.gitignore        |   1 +
>  tools/testing/selftests/kvm/Makefile          |   1 +
>  .../selftests/kvm/aarch64/arch_timer.c        | 382 ++++++++++++++++++
>  3 files changed, 384 insertions(+)
>  create mode 100644 tools/testing/selftests/kvm/aarch64/arch_timer.c
> 
> diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
> index 0709af0144c8..5f6cf0c76cf8 100644
> --- a/tools/testing/selftests/kvm/.gitignore
> +++ b/tools/testing/selftests/kvm/.gitignore
> @@ -1,4 +1,5 @@
>  # SPDX-License-Identifier: GPL-2.0-only
> +/aarch64/arch_timer
>  /aarch64/debug-exceptions
>  /aarch64/get-reg-list
>  /aarch64/vgic_init
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index a170166334a3..62a2c3e4b50c 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -84,6 +84,7 @@ TEST_GEN_PROGS_x86_64 += set_memory_region_test
>  TEST_GEN_PROGS_x86_64 += steal_time
>  TEST_GEN_PROGS_x86_64 += kvm_binary_stats_test
>  
> +TEST_GEN_PROGS_aarch64 += aarch64/arch_timer
>  TEST_GEN_PROGS_aarch64 += aarch64/debug-exceptions
>  TEST_GEN_PROGS_aarch64 += aarch64/get-reg-list
>  TEST_GEN_PROGS_aarch64 += aarch64/vgic_init
> diff --git a/tools/testing/selftests/kvm/aarch64/arch_timer.c b/tools/testing/selftests/kvm/aarch64/arch_timer.c
> new file mode 100644
> index 000000000000..88333fe1e567
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/aarch64/arch_timer.c
> @@ -0,0 +1,382 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * arch_timer.c - Tests the aarch64 timer IRQ functionality
> + *
> + * The test validates both the virtual and physical timer IRQs using
> + * CVAL and TVAL registers. This consitutes the four stages in the test.
> + * The guest's main thread configures the timer interrupt for a stage
> + * and waits for it to fire, with a timeout equal to the timer period.
> + * It asserts that the timeout doesn't exceed the timer period.
> + *
> + * On the other hand, upon receipt of an interrupt, the guest's interrupt
> + * handler validates the interrupt by checking if the architectural state
> + * is in compliance with the specifications.
> + *
> + * The test provides command-line options to configure the timer's
> + * period (-p), number of vCPUs (-n), and iterations per stage (-i).
> + *
> + * Copyright (c) 2021, Google LLC.
> + */
> +
> +#define _GNU_SOURCE
> +
> +#include <stdlib.h>
> +#include <pthread.h>
> +#include <linux/kvm.h>
> +#include <linux/sizes.h>
> +
> +#include "kvm_util.h"
> +#include "processor.h"
> +#include "delay.h"
> +#include "arch_timer.h"
> +#include "gic.h"
> +
> +#define NR_VCPUS_DEF			4
> +#define NR_TEST_ITERS_DEF		5
> +#define TIMER_TEST_PERIOD_MS_DEF	10
> +#define TIMER_TEST_ERR_MARGIN_US	100
> +
> +struct test_args {
> +	int nr_vcpus;
> +	int nr_iter;
> +	int timer_period_ms;
> +};
> +
> +static struct test_args test_args = {
> +	.nr_vcpus = NR_VCPUS_DEF,
> +	.nr_iter = NR_TEST_ITERS_DEF,
> +	.timer_period_ms = TIMER_TEST_PERIOD_MS_DEF,
> +};
> +
> +#define msecs_to_usecs(msec)		((msec) * 1000LL)
> +
> +#define VTIMER_IRQ			27
> +#define PTIMER_IRQ			30
> +
> +#define REDIST_REGION_ATTR_ADDR(count, base, flags, index) \
> +	(((uint64_t)(count) << 52) | \
> +	((uint64_t)((base) >> 16) << 16) | \
> +	((uint64_t)(flags) << 12) | \
> +	index)
> +
> +#define GICD_BASE_GPA			0x8000000ULL
> +#define GICR_BASE_GPA			0x80A0000ULL
> +
> +enum guest_stage {
> +	GUEST_STAGE_VTIMER_CVAL = 1,
> +	GUEST_STAGE_VTIMER_TVAL,
> +	GUEST_STAGE_PTIMER_CVAL,
> +	GUEST_STAGE_PTIMER_TVAL,
> +	GUEST_STAGE_MAX,
> +};
> +
> +/* Sahred variables between host and guest */
> +struct test_vcpu_shared_data {
> +	int nr_iter;
> +	enum guest_stage guest_stage;
> +	uint64_t xcnt;
> +};
> +
> +struct test_vcpu {
> +	uint32_t vcpuid;
> +	pthread_t pt_vcpu_run;
> +	struct kvm_vm *vm;
> +};
> +
> +static struct test_vcpu test_vcpu[KVM_MAX_VCPUS];
> +static struct test_vcpu_shared_data vcpu_shared_data[KVM_MAX_VCPUS];
> +
> +static void
> +guest_configure_timer_action(struct test_vcpu_shared_data *shared_data)
> +{
> +	switch (shared_data->guest_stage) {
> +	case GUEST_STAGE_VTIMER_CVAL:
> +		timer_set_next_cval_ms(VIRTUAL, test_args.timer_period_ms);
> +		shared_data->xcnt = timer_get_cntct(VIRTUAL);
> +		timer_set_ctl(VIRTUAL, CTL_ENABLE);
> +		break;
> +	case GUEST_STAGE_VTIMER_TVAL:
> +		timer_set_next_tval_ms(VIRTUAL, test_args.timer_period_ms);
> +		shared_data->xcnt = timer_get_cntct(VIRTUAL);
> +		timer_set_ctl(VIRTUAL, CTL_ENABLE);
> +		break;
> +	case GUEST_STAGE_PTIMER_CVAL:
> +		timer_set_next_cval_ms(PHYSICAL, test_args.timer_period_ms);
> +		shared_data->xcnt = timer_get_cntct(PHYSICAL);
> +		timer_set_ctl(PHYSICAL, CTL_ENABLE);
> +		break;
> +	case GUEST_STAGE_PTIMER_TVAL:
> +		timer_set_next_tval_ms(PHYSICAL, test_args.timer_period_ms);
> +		shared_data->xcnt = timer_get_cntct(PHYSICAL);
> +		timer_set_ctl(PHYSICAL, CTL_ENABLE);
> +		break;
> +	default:
> +		GUEST_ASSERT(0);
> +	}
> +}
> +
> +static void guest_validate_irq(unsigned int intid,
> +				struct test_vcpu_shared_data *shared_data)
> +{
> +	enum guest_stage stage = shared_data->guest_stage;
> +	uint64_t xcnt = 0, xcnt_diff_us, cval = 0;
> +	unsigned long xctl = 0;
> +	unsigned int timer_irq = 0;
> +
> +	if (stage == GUEST_STAGE_VTIMER_CVAL ||
> +		stage == GUEST_STAGE_VTIMER_TVAL) {
> +		xctl = timer_get_ctl(VIRTUAL);
> +		timer_set_ctl(VIRTUAL, CTL_IMASK);
> +		xcnt = timer_get_cntct(VIRTUAL);
> +		cval = timer_get_cval(VIRTUAL);
> +		timer_irq = VTIMER_IRQ;
> +	} else if (stage == GUEST_STAGE_PTIMER_CVAL ||
> +		stage == GUEST_STAGE_PTIMER_TVAL) {
> +		xctl = timer_get_ctl(PHYSICAL);
> +		timer_set_ctl(PHYSICAL, CTL_IMASK);
> +		xcnt = timer_get_cntct(PHYSICAL);
> +		cval = timer_get_cval(PHYSICAL);
> +		timer_irq = PTIMER_IRQ;
> +	} else {
> +		GUEST_ASSERT(0);
> +	}
> +
> +	xcnt_diff_us = cycles_to_usec(xcnt - shared_data->xcnt);
> +
> +	/* Make sure we are dealing with the correct timer IRQ */
> +	GUEST_ASSERT_2(intid == timer_irq, intid, timer_irq);
> +
> +	/* Basic 'timer codition met' check */
> +	GUEST_ASSERT_3(xcnt >= cval, xcnt, cval, xcnt_diff_us);
> +	GUEST_ASSERT_1(xctl & CTL_ISTATUS, xctl);
> +}
> +
> +static void guest_irq_handler(struct ex_regs *regs)
> +{
> +	unsigned int intid = gic_get_and_ack_irq();
> +	uint32_t cpu = get_vcpuid();
> +	struct test_vcpu_shared_data *shared_data = &vcpu_shared_data[cpu];
> +
> +	guest_validate_irq(intid, shared_data);
> +
> +	WRITE_ONCE(shared_data->nr_iter, shared_data->nr_iter + 1);
> +
> +	gic_set_eoi(intid);
> +}
> +
> +static void guest_run_stage(struct test_vcpu_shared_data *shared_data,
> +				enum guest_stage stage)
> +{
> +	uint32_t irq_iter, config_iter;
> +
> +	shared_data->guest_stage = stage;
> +	shared_data->nr_iter = 0;
> +
> +	for (config_iter = 0; config_iter < test_args.nr_iter; config_iter++) {
> +		/* Setup the next interrupt */
> +		guest_configure_timer_action(shared_data);
> +
> +		/* Setup a timeout for the interrupt to arrive */
> +		udelay(msecs_to_usecs(test_args.timer_period_ms) +
> +			TIMER_TEST_ERR_MARGIN_US);
> +
> +		irq_iter = READ_ONCE(shared_data->nr_iter);
> +		GUEST_ASSERT_2(config_iter + 1 == irq_iter,
> +				config_iter + 1, irq_iter);
> +	};
> +}
> +
> +static void guest_code(void)
> +{
> +	uint32_t cpu = get_vcpuid();
> +	struct test_vcpu_shared_data *shared_data = &vcpu_shared_data[cpu];
> +
> +	local_irq_disable();
> +
> +	gic_init(GIC_V3, test_args.nr_vcpus,
> +		(void *)GICD_BASE_GPA, (void *)GICR_BASE_GPA);
> +
> +	timer_set_ctl(VIRTUAL, CTL_IMASK);
> +	timer_set_ctl(PHYSICAL, CTL_IMASK);
> +
> +	gic_irq_enable(VTIMER_IRQ);
> +	gic_irq_enable(PTIMER_IRQ);
> +	local_irq_enable();
> +
> +	guest_run_stage(shared_data, GUEST_STAGE_VTIMER_CVAL);
> +	guest_run_stage(shared_data, GUEST_STAGE_VTIMER_TVAL);
> +	guest_run_stage(shared_data, GUEST_STAGE_PTIMER_CVAL);
> +	guest_run_stage(shared_data, GUEST_STAGE_PTIMER_TVAL);
> +
> +	GUEST_DONE();
> +}
> +
> +static void *test_vcpu_run(void *arg)
> +{
> +	struct ucall uc;
> +	struct test_vcpu *vcpu = arg;
> +	struct kvm_vm *vm = vcpu->vm;
> +	uint32_t vcpuid = vcpu->vcpuid;
> +	struct test_vcpu_shared_data *shared_data = &vcpu_shared_data[vcpuid];
> +
> +	vcpu_run(vm, vcpuid);
> +
> +	switch (get_ucall(vm, vcpuid, &uc)) {
> +	case UCALL_SYNC:
> +	case UCALL_DONE:
> +		break;
> +	case UCALL_ABORT:
> +		sync_global_from_guest(vm, *shared_data);
> +		TEST_ASSERT(false,
> +			"%s at %s:%ld\n\tvalues: %lu, %lu; %lu, vcpu: %u; stage: %u; iter: %u",
> +			(const char *)uc.args[0], __FILE__, uc.args[1],
> +			uc.args[2], uc.args[3], uc.args[4], vcpuid,
> +			shared_data->guest_stage, shared_data->nr_iter);
> +		break;
> +	default:
> +		TEST_FAIL("Unexpected guest exit\n");
> +	}
> +
> +	return NULL;
> +}
> +
> +static void test_run(struct kvm_vm *vm)
> +{
> +	int i, ret;
> +
> +	for (i = 0; i < test_args.nr_vcpus; i++) {
> +		ret = pthread_create(&test_vcpu[i].pt_vcpu_run, NULL,
> +				test_vcpu_run, &test_vcpu[i]);
> +		TEST_ASSERT(!ret, "Failed to create vCPU-%d pthread\n", i);
> +	}
> +
> +	for (i = 0; i < test_args.nr_vcpus; i++)
> +		pthread_join(test_vcpu[i].pt_vcpu_run, NULL);
> +}
> +
> +static void test_vm_setup_gic(struct kvm_vm *vm, unsigned int n_gicr_pages)

I think it's nicer if this takes nr_vcpus instead of gicr_pages.

And, it possible, it would be doubly nice if it could be be made a
library function (e.g., inside lib/aarch64/vgic.c?).

> +{
> +	uint64_t addr;
> +	int gic_fd;
> +
> +	gic_fd = kvm_create_device(vm, KVM_DEV_TYPE_ARM_VGIC_V3, false);
> +
> +	addr = GICD_BASE_GPA;
> +	kvm_device_access(gic_fd, KVM_DEV_ARM_VGIC_GRP_ADDR,
> +				KVM_VGIC_V3_ADDR_TYPE_DIST, &addr, true);
> +	virt_pg_map(vm, GICD_BASE_GPA, GICD_BASE_GPA);

Not really a big deal at the moment, but if KVM implemented ESPIs, then
a 4k page wouldn't be enough. Why not map 64Ks as there's space for it?

> +
> +	addr = REDIST_REGION_ATTR_ADDR(test_args.nr_vcpus, GICR_BASE_GPA, 0, 0);
> +	kvm_device_access(gic_fd, KVM_DEV_ARM_VGIC_GRP_ADDR,
> +			KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION, &addr, true);
> +	virt_map(vm, GICR_BASE_GPA, GICR_BASE_GPA, n_gicr_pages);
> +
> +	kvm_device_access(gic_fd, KVM_DEV_ARM_VGIC_GRP_CTRL,
> +				KVM_DEV_ARM_VGIC_CTRL_INIT, NULL, true);
> +}
> +
> +static struct kvm_vm *test_vm_create(void)
> +{
> +	struct kvm_vm *vm;
> +	unsigned int i, n_gicr_pages;
> +	int nr_vcpus = test_args.nr_vcpus;
> +
> +	/* Reserve additional pages for GICR MMIO based on nr_vcpus */
> +	n_gicr_pages = vm_calc_num_guest_pages(VM_MODE_DEFAULT,
> +						2 * SZ_64K * nr_vcpus);

Might be better to use vm_get_page_size instead as it doesn't need the
mode arg. Note that you would have to call it after creating the vm
(vm_create..), but the nice thing is that that call uses the actual mode
that the vm was created with. I propose moving this pages calculation to
inside test_vm_setup_gic, which could take the number of vcpus as an arg
(instead of nr_pages).

> +
> +	vm = vm_create_default_with_vcpus(nr_vcpus, n_gicr_pages, 0,
> +						guest_code, NULL);
> +
> +	vm_init_descriptor_tables(vm);
> +	vm_install_exception_handler(vm, VECTOR_IRQ_CURRENT, guest_irq_handler);
> +
> +	for (i = 0; i < nr_vcpus; i++) {
> +		vcpu_init_descriptor_tables(vm, i);
> +
> +		test_vcpu[i].vcpuid = i;
> +		test_vcpu[i].vm = vm;
> +	}
> +
> +	ucall_init(vm, NULL);
> +	test_vm_setup_gic(vm, n_gicr_pages);
> +
> +	/* Make all the test's cmdline args visible to the guest */
> +	sync_global_to_guest(vm, test_args);
> +
> +	return vm;
> +}
> +
> +static void test_print_help(char *name)
> +{
> +	pr_info("Usage: %s [-h] [-n nr_vcpus] [-i iterations] [-p timer_period_ms]\n",
> +		name);
> +	pr_info("\t-n: Number of vCPUs to configure (default: %u; max: %u)\n",
> +		NR_VCPUS_DEF, KVM_MAX_VCPUS);
> +	pr_info("\t-i: Number of iterations per stage (default: %u)\n",
> +		NR_TEST_ITERS_DEF);
> +	pr_info("\t-p: Periodicity (in ms) of the guest timer (default: %u)\n",
> +		TIMER_TEST_PERIOD_MS_DEF);
> +	pr_info("\t-h: print this help screen\n");
> +}
> +
> +static bool parse_args(int argc, char *argv[])
> +{
> +	int opt;
> +
> +	while ((opt = getopt(argc, argv, "hn:i:p:")) != -1) {
> +		switch (opt) {
> +		case 'n':
> +			test_args.nr_vcpus = atoi(optarg);
> +			if (test_args.nr_vcpus <= 0) {
> +				pr_info("Positive value needed for -n\n");
> +				goto err;
> +			} else if (test_args.nr_vcpus > KVM_MAX_VCPUS) {
> +				pr_info("Max allowed vCPUs: %u\n",
> +					KVM_MAX_VCPUS);
> +				goto err;
> +			}
> +			break;
> +		case 'i':
> +			test_args.nr_iter = atoi(optarg);
> +			if (test_args.nr_iter <= 0) {
> +				pr_info("Positive value needed for -i\n");
> +				goto err;
> +			}
> +			break;
> +		case 'p':
> +			test_args.timer_period_ms = atoi(optarg);
> +			if (test_args.timer_period_ms <= 0) {
> +				pr_info("Positive value needed for -p\n");
> +				goto err;
> +			}
> +			break;
> +		case 'h':
> +		default:
> +			goto err;
> +		}
> +	}
> +
> +	return true;
> +
> +err:
> +	test_print_help(argv[0]);
> +	return false;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> +	struct kvm_vm *vm;
> +
> +	/* Tell stdout not to buffer its content */
> +	setbuf(stdout, NULL);
> +
> +	if (!parse_args(argc, argv))
> +		exit(KSFT_SKIP);
> +
> +	vm = test_vm_create();
> +	test_run(vm);
> +	kvm_vm_free(vm);
> +
> +	return 0;
> +}
> -- 
> 2.33.0.rc1.237.g0d66db33f3-goog
> 

Thanks,
Ricardo
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