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bh=XqHjuGgRhd53kfR40OyBo5y76L66nYApGqlRgV8dib0=; b=ESvK/uX+YIwCVneADJKST1jb+0+hITzywv/Hui1+vpMiRqK0d0kljPMxxe74mU74Ey P1v7gYshIUSh3KCyEZx9FVWMyw2Xd0awHOyC+SQIyTg0OHiiPjUkhc7MYszpKTi4e8vx YwdeOmRGQc2P4US4Y5zWv2tZiu6Xmbr6Rj9EH2BXEMWx5m9LRBeNqbIRUMLSR6XZBjnb 8Fun6QbFaT4WZjrqBWqvagi4zT7bzVYE9T6I3pOX7zhqpVnLbIZxtDRwuSfhOEL36rWb 5B47DLBHuV6wVgmWrF87UVNjDAbQOdEWHAd63vsUAO1OmUODIuGLIaj1kYx68fNS8EMa Crpg== X-Gm-Message-State: AOAM531tWROLzpVxU6Tb68EnDZrwUT8/GSM453ciZAPkiWO3CKuUFGdn /QcdUJCe4yZBlL/FxJ/pcAbg8MCwuQl01fIBp8BahA== X-Google-Smtp-Source: ABdhPJzDM0my2zsTOKwfUsRrFm3fZu5v6rZyyixD1c3rSO5zAxCR1j0GXOzF7oglZEKoEkqrXgG18A6yuTg+n0twgoU= X-Received: by 2002:a25:21c5:: with SMTP id h188mr4984145ybh.23.1631208839114; Thu, 09 Sep 2021 10:33:59 -0700 (PDT) MIME-Version: 1.0 References: <20210909013818.1191270-1-rananta@google.com> <20210909013818.1191270-17-rananta@google.com> <20210909134520.yxrjestdwsishce2@gator> In-Reply-To: <20210909134520.yxrjestdwsishce2@gator> From: Raghavendra Rao Ananta Date: Thu, 9 Sep 2021 10:33:47 -0700 Message-ID: Subject: Re: [PATCH v4 16/18] KVM: arm64: selftests: arch_timer: Support vCPU migration To: Andrew Jones Cc: Paolo Bonzini , Marc Zyngier , James Morse , Alexandru Elisei , Suzuki K Poulose , Catalin Marinas , Will Deacon , Peter Shier , Ricardo Koller , Oliver Upton , Reiji Watanabe , Jing Zhang , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 9, 2021 at 6:45 AM Andrew Jones wrote: > > On Thu, Sep 09, 2021 at 01:38:16AM +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 | 113 +++++++++++++++++- > > 1 file changed, 112 insertions(+), 1 deletion(-) > > > > diff --git a/tools/testing/selftests/kvm/aarch64/arch_timer.c b/tools/testing/selftests/kvm/aarch64/arch_timer.c > > index 6141c387e6dc..aac7bcea4352 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" > > @@ -36,17 +40,20 @@ > > #define NR_TEST_ITERS_DEF 5 > > #define TIMER_TEST_PERIOD_MS_DEF 10 > > #define TIMER_TEST_ERR_MARGIN_US 100 > > +#define TIMER_TEST_MIGRATION_FREQ_MS 2 > > > > 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 = TIMER_TEST_MIGRATION_FREQ_MS, > > }; > > > > #define msecs_to_usecs(msec) ((msec) * 1000LL) > > @@ -81,6 +88,9 @@ 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 +226,11 @@ 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: > > @@ -234,9 +249,76 @@ 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; > > +} > > Missing blank line here. > > > +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); > > + > > + pr_debug("Migrating vCPU: %u to pCPU: %u\n", vcpu->vcpuid, new_pcpu); > > + > > + 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); > > + > > + return ret; > > +} > > Missing blank line here. > > > +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, > > @@ -244,8 +326,23 @@ 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 +383,8 @@ 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: %u)\n", > > + TIMER_TEST_MIGRATION_FREQ_MS); > > pr_info("\t-h: print this help screen\n"); > > } > > > > @@ -293,7 +392,7 @@ 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 +419,13 @@ 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 +449,11 @@ int main(int argc, char *argv[]) > > if (!parse_args(argc, argv)) > > exit(KSFT_SKIP); > > > > + if (get_nprocs() < 2) { > > Even though the chance of being on a uniprocessor is low and the migration > test is now on by default, we could still do > > if (test_args.migration_freq_ms && get_nprocs() < 2) > huh, I had the check earlier; must have dropped it somewhere. Will place it back. And I'll fix all the blank line comments. Regards, Raghavendra > since that's why the skip message says it needs two cpus. > > > + 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 > > > > Reviewed-by: Andrew Jones > > Thanks, > drew >