On Thu, Mar 16, 2023 at 3:29 PM Colton Lewis <coltonlewis@xxxxxxxxxx> wrote:
>
> Provide a generic function to read the system counter from the guest
> for timing purposes. A common and important way to measure guest
> performance is to measure the amount of time different actions take in
> the guest. Provide also a mathematical conversion from cycles to
> nanoseconds and a macro for timing individual statements.
>
> Substitute the previous custom implementation of a similar function in
May be specify specific name: guest_read_system_counter()
> system_counter_offset_test with this new implementation.
>
> Signed-off-by: Colton Lewis <coltonlewis@xxxxxxxxxx>
> ---
> .../testing/selftests/kvm/include/kvm_util.h | 15 ++++++++++
> tools/testing/selftests/kvm/lib/kvm_util.c | 30 +++++++++++++++++++
> .../kvm/system_counter_offset_test.c | 10 ++-----
> 3 files changed, 47 insertions(+), 8 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> index c9286811a4cb..8b478eabee4c 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util.h
> @@ -10,4 +10,19 @@
> #include "kvm_util_base.h"
> #include "ucall_common.h"
>
> +#if defined(__aarch64__) || defined(__x86_64__)
> +
> +uint64_t cycles_read(void);
> +double cycles_to_ns(struct kvm_vcpu *vcpu, double cycles);
> +
> +#define MEASURE_CYCLES(x) \
> + ({ \
> + uint64_t start; \
> + start = cycles_read(); \
> + x; \
> + cycles_read() - start; \
> + })
> +
MEASURE_CYCLES should be moved to the next patch where it is getting
used. Does it have to be macro or can it be replaced with a function?
> +#endif
> +
> #endif /* SELFTEST_KVM_UTIL_H */
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index 3ea24a5f4c43..780481a92efe 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -2135,3 +2135,34 @@ void __attribute((constructor)) kvm_selftest_init(void)
>
> kvm_selftest_arch_init();
> }
> +
> +#if defined(__aarch64__)
> +
> +#include "arch_timer.h"
> +
> +uint64_t cycles_read(void)
> +{
> + return timer_get_cntct(VIRTUAL);
> +}
> +
> +double cycles_to_ns(struct kvm_vcpu *vcpu, double cycles)
> +{
> + return cycles * (1e9 / timer_get_cntfrq());
> +}
> +
> +#elif defined(__x86_64__)
> +
> +#include "processor.h"
> +
> +uint64_t cycles_read(void)
> +{
> + return rdtsc();
> +}
> +
> +double cycles_to_ns(struct kvm_vcpu *vcpu, double cycles)
> +{
> + uint64_t tsc_khz = __vcpu_ioctl(vcpu, KVM_GET_TSC_KHZ, NULL);
> +
> + return cycles * (1e9 / (tsc_khz * 1000));
> +}
> +#endif
As Andrew noted, these should be in the respective processor files.
