| Message ID | 20210719184949.1385910-13-oupton@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: Add idempotent controls for migrating system counter state | expand |
On Mon, Jul 19, 2021 at 06:49:49PM +0000, Oliver Upton wrote: > 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 <ricarkol@google.com> > Signed-off-by: Oliver Upton <oupton@google.com> > --- > 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 alphabetic order please > /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 alphabetic order please > 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 <asm/kvm.h> > +#include <linux/kvm.h> > +#include <stdio.h> > +#include <stdint.h> > +#include <stdlib.h> > +#include <unistd.h> > + > +#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"); UCALL_DONE would assert, but we never do a UCALL_DONE because we're entering the guest nr_iterations times but [would] exit it 2 * nr_iterations times before GUEST_DONE() gets called. IOW, the logic of the run loop looks like it could use some cleanup. > + 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); > +} > -- > 2.32.0.402.g57bb445576-goog > > _______________________________________________ > kvmarm mailing list > kvmarm@lists.cs.columbia.edu > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm > Thanks, drew
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 <asm/kvm.h> +#include <linux/kvm.h> +#include <stdio.h> +#include <stdint.h> +#include <stdlib.h> +#include <unistd.h> + +#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); +}