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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=Pe/S/uzS2wg1+TTNiX12UiCpgPQMvxwQXCZew3HD/LI=; b=k2cz+gJYh73bWoca/MHVWDibImzYE8kZZcdtG9IzSJSLw2pOJvlr6FCa+UAmtD4wxR Bbasfocipn5I6u9RwaL9C+zTcdKuzfmcU1snt/RHz9WGFbINbScxy6NVPBScFYmxbiwd knzmecwuQ32blsVJ91cChXavS8qRG+E8IHBPmgx9HjWBs5sQt5v2HRGhmksGAqS8ihik pi68jUL+gjD0h422L9uVBRYDKitsNF1QZx9775To6ycw37mrlzfgDOZ6ZbovDKdv8BEK 7YvsGTTMA1EZRRYlFRa6I2KPUmt4G6csF/uqB0h7ZnRZqCtA21O+2R3pYtRuRH9iSWAC r5LQ== X-Gm-Message-State: AOAM533W1U51jOK7jjSTERsJMC9O3m932VXsLwNycRXllOxXwBaD6ZCq vlbaQdkjPjosRUhp0F0jS4/uNOQIBA0= X-Google-Smtp-Source: ABdhPJyQcHkAB6MPdhvQdWJtxf9obMBiVoOlTPVWctV8cgSO62KQrItWlsn03gEnh4XWHeOfr1ATWxnMN2I= X-Received: from oupton.c.googlers.com ([fda3:e722:ac3:cc00:2b:ff92:c0a8:404]) (user=oupton job=sendgmr) by 2002:a25:9887:: with SMTP id l7mr14704635ybo.191.1626470811681; Fri, 16 Jul 2021 14:26:51 -0700 (PDT) Date: Fri, 16 Jul 2021 21:26:29 +0000 In-Reply-To: <20210716212629.2232756-1-oupton@google.com> Message-Id: <20210716212629.2232756-13-oupton@google.com> Mime-Version: 1.0 References: <20210716212629.2232756-1-oupton@google.com> X-Mailer: git-send-email 2.32.0.402.g57bb445576-goog Subject: [PATCH v2 12/12] selftests: KVM: Add counter emulation benchmark From: Oliver Upton To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu Cc: Paolo Bonzini , Sean Christopherson , Marc Zyngier , Peter Shier , Jim Mattson , David Matlack , Ricardo Koller , Jing Zhang , Raghavendra Rao Anata , James Morse , Alexandru Elisei , Suzuki K Poulose , linux-arm-kernel@lists.infradead.org, Oliver Upton X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210716_142653_426146_09448BBD X-CRM114-Status: GOOD ( 20.97 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Add a test case for counter emulation on arm64. A side effect of how KVM handles physical counter offsetting on non-ECV systems is that the virtual counter will always hit hardware and the physical could be emulated. Force emulation by writing a nonzero offset to the physical counter and compare the elapsed cycles to a direct read of the hardware register. Reviewed-by: Ricardo Koller Signed-off-by: Oliver Upton --- tools/testing/selftests/kvm/.gitignore | 1 + tools/testing/selftests/kvm/Makefile | 1 + .../kvm/aarch64/counter_emulation_benchmark.c | 215 ++++++++++++++++++ 3 files changed, 217 insertions(+) create mode 100644 tools/testing/selftests/kvm/aarch64/counter_emulation_benchmark.c diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore index 2752813d5090..1d811c6a769b 100644 --- a/tools/testing/selftests/kvm/.gitignore +++ b/tools/testing/selftests/kvm/.gitignore @@ -1,5 +1,6 @@ # SPDX-License-Identifier: GPL-2.0-only /aarch64/debug-exceptions +/aarch64/counter_emulation_benchmark /aarch64/get-reg-list /aarch64/vgic_init /s390x/memop diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile index d89908108c97..e560a3e74bc2 100644 --- a/tools/testing/selftests/kvm/Makefile +++ b/tools/testing/selftests/kvm/Makefile @@ -86,6 +86,7 @@ TEST_GEN_PROGS_x86_64 += kvm_binary_stats_test TEST_GEN_PROGS_x86_64 += system_counter_offset_test TEST_GEN_PROGS_aarch64 += aarch64/debug-exceptions +TEST_GEN_PROGS_aarch64 += aarch64/counter_emulation_benchmark TEST_GEN_PROGS_aarch64 += aarch64/get-reg-list TEST_GEN_PROGS_aarch64 += aarch64/vgic_init TEST_GEN_PROGS_aarch64 += demand_paging_test diff --git a/tools/testing/selftests/kvm/aarch64/counter_emulation_benchmark.c b/tools/testing/selftests/kvm/aarch64/counter_emulation_benchmark.c new file mode 100644 index 000000000000..73aeb6cdebfe --- /dev/null +++ b/tools/testing/selftests/kvm/aarch64/counter_emulation_benchmark.c @@ -0,0 +1,215 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * counter_emulation_benchmark.c -- test to measure the effects of counter + * emulation on guest reads of the physical counter. + * + * Copyright (c) 2021, Google LLC. + */ + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include + +#include "kvm_util.h" +#include "processor.h" +#include "test_util.h" + +#define VCPU_ID 0 + +static struct counter_values { + uint64_t cntvct_start; + uint64_t cntpct; + uint64_t cntvct_end; +} counter_values; + +static uint64_t nr_iterations = 1000; + +static void do_test(void) +{ + /* + * Open-coded approach instead of using helper methods to keep a tight + * interval around the physical counter read. + */ + asm volatile("isb\n\t" + "mrs %[cntvct_start], cntvct_el0\n\t" + "isb\n\t" + "mrs %[cntpct], cntpct_el0\n\t" + "isb\n\t" + "mrs %[cntvct_end], cntvct_el0\n\t" + "isb\n\t" + : [cntvct_start] "=r"(counter_values.cntvct_start), + [cntpct] "=r"(counter_values.cntpct), + [cntvct_end] "=r"(counter_values.cntvct_end)); +} + +static void guest_main(void) +{ + int i; + + for (i = 0; i < nr_iterations; i++) { + do_test(); + GUEST_SYNC(i); + } + + for (i = 0; i < nr_iterations; i++) { + do_test(); + GUEST_SYNC(i); + } + + GUEST_DONE(); +} + +static bool enter_guest(struct kvm_vm *vm) +{ + struct ucall uc; + + vcpu_ioctl(vm, VCPU_ID, KVM_RUN, NULL); + + switch (get_ucall(vm, VCPU_ID, &uc)) { + case UCALL_DONE: + return true; + case UCALL_SYNC: + break; + case UCALL_ABORT: + TEST_ASSERT(false, "%s at %s:%ld", (const char *)uc.args[0], + __FILE__, uc.args[1]); + break; + default: + TEST_ASSERT(false, "unexpected exit: %s", + exit_reason_str(vcpu_state(vm, VCPU_ID)->exit_reason)); + break; + } + + /* more work to do in the guest */ + return false; +} + +static double counter_frequency(void) +{ + uint32_t freq; + + asm volatile("mrs %0, cntfrq_el0" + : "=r" (freq)); + + return freq / 1000000.0; +} + +static void log_csv(FILE *csv, bool trapped) +{ + double freq = counter_frequency(); + + fprintf(csv, "%s,%.02f,%lu,%lu,%lu\n", + trapped ? "true" : "false", freq, + counter_values.cntvct_start, + counter_values.cntpct, + counter_values.cntvct_end); +} + +static double run_loop(struct kvm_vm *vm, FILE *csv, bool trapped) +{ + double avg = 0; + int i; + + for (i = 0; i < nr_iterations; i++) { + uint64_t delta; + + TEST_ASSERT(!enter_guest(vm), "guest exited unexpectedly"); + sync_global_from_guest(vm, counter_values); + + if (csv) + log_csv(csv, trapped); + + delta = counter_values.cntvct_end - counter_values.cntvct_start; + avg = ((avg * i) + delta) / (i + 1); + } + + return avg; +} + +static void setup_counter(struct kvm_vm *vm, uint64_t offset) +{ + vcpu_access_device_attr(vm, VCPU_ID, KVM_ARM_VCPU_TIMER_CTRL, + KVM_ARM_VCPU_TIMER_OFFSET_PTIMER, &offset, + true); +} + +static void run_tests(struct kvm_vm *vm, FILE *csv) +{ + double avg_trapped, avg_native, freq; + + freq = counter_frequency(); + + if (csv) + fputs("trapped,freq_mhz,cntvct_start,cntpct,cntvct_end\n", csv); + + /* no physical offsetting; kvm allows reads of cntpct_el0 */ + setup_counter(vm, 0); + avg_native = run_loop(vm, csv, false); + + /* force emulation of the physical counter */ + setup_counter(vm, 1); + avg_trapped = run_loop(vm, csv, true); + + TEST_ASSERT(enter_guest(vm), "guest didn't run to completion"); + pr_info("%lu iterations: average cycles (@%.02fMHz) native: %.02f, trapped: %.02f\n", + nr_iterations, freq, avg_native, avg_trapped); +} + +static void usage(const char *program_name) +{ + fprintf(stderr, + "Usage: %s [-h] [-o csv_file] [-n iterations]\n" + " -h prints this message\n" + " -n number of test iterations (default: %lu)\n" + " -o csv file to write data\n", + program_name, nr_iterations); +} + +int main(int argc, char **argv) +{ + struct kvm_vm *vm; + FILE *csv = NULL; + int opt; + + while ((opt = getopt(argc, argv, "hn:o:")) != -1) { + switch (opt) { + case 'o': + csv = fopen(optarg, "w"); + if (!csv) { + fprintf(stderr, "failed to open file '%s': %d\n", + optarg, errno); + exit(1); + } + break; + case 'n': + nr_iterations = strtoul(optarg, NULL, 0); + break; + default: + fprintf(stderr, "unrecognized option: '-%c'\n", opt); + /* fallthrough */ + case 'h': + usage(argv[0]); + exit(1); + } + } + + vm = vm_create_default(VCPU_ID, 0, guest_main); + sync_global_to_guest(vm, nr_iterations); + ucall_init(vm, NULL); + + if (_vcpu_has_device_attr(vm, VCPU_ID, KVM_ARM_VCPU_TIMER_CTRL, + KVM_ARM_VCPU_TIMER_OFFSET_PTIMER)) { + print_skip("KVM_ARM_VCPU_TIMER_OFFSET_PTIMER not supported."); + exit(KSFT_SKIP); + } + + run_tests(vm, csv); + kvm_vm_free(vm); + + if (csv) + fclose(csv); +}