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[31.30.174.132]) by smtp.gmail.com with ESMTPSA id n2sm2842024edi.32.2021.09.03.04.05.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Sep 2021 04:05:16 -0700 (PDT) Date: Fri, 3 Sep 2021 13:05:14 +0200 From: Andrew Jones To: Raghavendra Rao Ananta Cc: Paolo Bonzini , Marc Zyngier , James Morse , Alexandru Elisei , Suzuki K Poulose , kvm@vger.kernel.org, Catalin Marinas , Peter Shier , linux-kernel@vger.kernel.org, Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v3 12/12] KVM: arm64: selftests: arch_timer: Support vCPU migration Message-ID: <20210903110514.22x3txynin5hg46z@gator.home> References: <20210901211412.4171835-1-rananta@google.com> <20210901211412.4171835-13-rananta@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210901211412.4171835-13-rananta@google.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Sep 01, 2021 at 09:14:12PM +0000, Raghavendra Rao Ananta wrote: > Since the timer stack (hardware and KVM) is per-CPU, there > are potential chances for races to occur when the scheduler > decides to migrate a vCPU thread to a different physical CPU. > Hence, include an option to stress-test this part as well by > forcing the vCPUs to migrate across physical CPUs in the > system at a particular rate. > > Originally, the bug for the fix with commit 3134cc8beb69d0d > ("KVM: arm64: vgic: Resample HW pending state on deactivation") > was discovered using arch_timer test with vCPU migrations and > can be easily reproduced. > > Signed-off-by: Raghavendra Rao Ananta > --- > .../selftests/kvm/aarch64/arch_timer.c | 108 +++++++++++++++++- > 1 file changed, 107 insertions(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/kvm/aarch64/arch_timer.c b/tools/testing/selftests/kvm/aarch64/arch_timer.c > index 1383f33850e9..de246c7afab2 100644 > --- a/tools/testing/selftests/kvm/aarch64/arch_timer.c > +++ b/tools/testing/selftests/kvm/aarch64/arch_timer.c > @@ -14,6 +14,8 @@ > * > * The test provides command-line options to configure the timer's > * period (-p), number of vCPUs (-n), and iterations per stage (-i). > + * To stress-test the timer stack even more, an option to migrate the > + * vCPUs across pCPUs (-m), at a particular rate, is also provided. > * > * Copyright (c) 2021, Google LLC. > */ > @@ -24,6 +26,8 @@ > #include > #include > #include > +#include > +#include > > #include "kvm_util.h" > #include "processor.h" > @@ -41,12 +45,14 @@ struct test_args { > int nr_vcpus; > int nr_iter; > int timer_period_ms; > + int migration_freq_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, > + .migration_freq_ms = 0, /* Turn off migrations by default */ I'd rather we enable good tests like these by default. > }; > > #define msecs_to_usecs(msec) ((msec) * 1000LL) > @@ -81,6 +87,9 @@ struct test_vcpu { > static struct test_vcpu test_vcpu[KVM_MAX_VCPUS]; > static struct test_vcpu_shared_data vcpu_shared_data[KVM_MAX_VCPUS]; > > +static unsigned long *vcpu_done_map; > +static pthread_mutex_t vcpu_done_map_lock; > + > static void > guest_configure_timer_action(struct test_vcpu_shared_data *shared_data) > { > @@ -216,6 +225,11 @@ static void *test_vcpu_run(void *arg) > > vcpu_run(vm, vcpuid); > > + /* Currently, any exit from guest is an indication of completion */ > + pthread_mutex_lock(&vcpu_done_map_lock); > + set_bit(vcpuid, vcpu_done_map); > + pthread_mutex_unlock(&vcpu_done_map_lock); > + > switch (get_ucall(vm, vcpuid, &uc)) { > case UCALL_SYNC: > case UCALL_DONE: > @@ -235,9 +249,73 @@ static void *test_vcpu_run(void *arg) > return NULL; > } > > +static uint32_t test_get_pcpu(void) > +{ > + uint32_t pcpu; > + unsigned int nproc_conf; > + cpu_set_t online_cpuset; > + > + nproc_conf = get_nprocs_conf(); > + sched_getaffinity(0, sizeof(cpu_set_t), &online_cpuset); > + > + /* Randomly find an available pCPU to place a vCPU on */ > + do { > + pcpu = rand() % nproc_conf; > + } while (!CPU_ISSET(pcpu, &online_cpuset)); > + > + return pcpu; > +} > +static int test_migrate_vcpu(struct test_vcpu *vcpu) > +{ > + int ret; > + cpu_set_t cpuset; > + uint32_t new_pcpu = test_get_pcpu(); > + > + CPU_ZERO(&cpuset); > + CPU_SET(new_pcpu, &cpuset); > + ret = pthread_setaffinity_np(vcpu->pt_vcpu_run, > + sizeof(cpuset), &cpuset); > + > + /* Allow the error where the vCPU thread is already finished */ > + TEST_ASSERT(ret == 0 || ret == ESRCH, > + "Failed to migrate the vCPU:%u to pCPU: %u; ret: %d\n", > + vcpu->vcpuid, new_pcpu, ret); It'd be good to collect stats for the two cases so we know how many vcpus we actually migrated with a successful setaffinity and how many just completed too early. If our stats don't look good, then we can adjust our timeouts and frequencies. > + > + return ret; > +} > +static void *test_vcpu_migration(void *arg) > +{ > + unsigned int i, n_done; > + bool vcpu_done; > + > + do { > + usleep(msecs_to_usecs(test_args.migration_freq_ms)); > + > + for (n_done = 0, i = 0; i < test_args.nr_vcpus; i++) { > + pthread_mutex_lock(&vcpu_done_map_lock); > + vcpu_done = test_bit(i, vcpu_done_map); > + pthread_mutex_unlock(&vcpu_done_map_lock); > + > + if (vcpu_done) { > + n_done++; > + continue; > + } > + > + test_migrate_vcpu(&test_vcpu[i]); > + } > + } while (test_args.nr_vcpus != n_done); > + > + return NULL; > +} > + > static void test_run(struct kvm_vm *vm) > { > int i, ret; > + pthread_t pt_vcpu_migration; > + > + pthread_mutex_init(&vcpu_done_map_lock, NULL); > + vcpu_done_map = bitmap_alloc(test_args.nr_vcpus); > + TEST_ASSERT(vcpu_done_map, "Failed to allocate vcpu done bitmap\n"); > > for (i = 0; i < test_args.nr_vcpus; i++) { > ret = pthread_create(&test_vcpu[i].pt_vcpu_run, NULL, > @@ -245,8 +323,23 @@ static void test_run(struct kvm_vm *vm) > TEST_ASSERT(!ret, "Failed to create vCPU-%d pthread\n", i); > } > > + /* Spawn a thread to control the vCPU migrations */ > + if (test_args.migration_freq_ms) { > + srand(time(NULL)); > + > + ret = pthread_create(&pt_vcpu_migration, NULL, > + test_vcpu_migration, NULL); > + TEST_ASSERT(!ret, "Failed to create the migration pthread\n"); > + } > + > + > for (i = 0; i < test_args.nr_vcpus; i++) > pthread_join(test_vcpu[i].pt_vcpu_run, NULL); > + > + if (test_args.migration_freq_ms) > + pthread_join(pt_vcpu_migration, NULL); > + > + bitmap_free(vcpu_done_map); > } > > static struct kvm_vm *test_vm_create(void) > @@ -286,6 +379,7 @@ static void test_print_help(char *name) > 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-m: Frequency (in ms) of vCPUs to migrate to different pCPU. 0 to turn off (default: 0)\n"); > pr_info("\t-h: print this help screen\n"); > } > > @@ -293,7 +387,7 @@ static bool parse_args(int argc, char *argv[]) > { > int opt; > > - while ((opt = getopt(argc, argv, "hn:i:p:")) != -1) { > + while ((opt = getopt(argc, argv, "hn:i:p:m:")) != -1) { > switch (opt) { > case 'n': > test_args.nr_vcpus = atoi(optarg); > @@ -320,6 +414,13 @@ static bool parse_args(int argc, char *argv[]) > goto err; > } > break; > + case 'm': > + test_args.migration_freq_ms = atoi(optarg); > + if (test_args.migration_freq_ms < 0) { > + pr_info("0 or positive value needed for -m\n"); > + goto err; > + } > + break; > case 'h': > default: > goto err; > @@ -343,6 +444,11 @@ int main(int argc, char *argv[]) > if (!parse_args(argc, argv)) > exit(KSFT_SKIP); > > + if (get_nprocs() < 2) { if (test_args.migration_freq_ms && get_nprocs() < 2) > + print_skip("At least two physical CPUs needed for vCPU migration"); > + exit(KSFT_SKIP); > + } > + > vm = test_vm_create(); > test_run(vm); > kvm_vm_free(vm); > -- > 2.33.0.153.gba50c8fa24-goog > Thanks, drew