Add a new arm64-specific trace clock using the cntvct register, similar to x64-tsc. This gives us: - A clock that is relatively fast (1GHz on armv8.6, 1-50MHz otherwise), monotonic, and resilient to low power modes. - It can be used to correlate events across cpus as well as across hypervisor and guests.
By using arch_timer_read_counter() we make sure that armv8.6 cpus use the less expensive CNTVCTSS_EL0, which cannot be accessed speculatively. Signed-off-by: Nicolas Saenz Julienne <[email protected]> --- arch/arm64/include/asm/trace_clock.h | 12 ++++++++++++ arch/arm64/kernel/Makefile | 2 +- arch/arm64/kernel/trace_clock.c | 12 ++++++++++++ 3 files changed, 25 insertions(+), 1 deletion(-) create mode 100644 arch/arm64/include/asm/trace_clock.h create mode 100644 arch/arm64/kernel/trace_clock.c diff --git a/arch/arm64/include/asm/trace_clock.h b/arch/arm64/include/asm/trace_clock.h new file mode 100644 index 000000000000..ce4a66d63108 --- /dev/null +++ b/arch/arm64/include/asm/trace_clock.h @@ -0,0 +1,12 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_ARM64_TRACE_CLOCK_H +#define _ASM_ARM64_TRACE_CLOCK_H + +#include <linux/types.h> + +extern u64 notrace trace_clock_arm64_cntvct(void); + +# define ARCH_TRACE_CLOCKS \ + { trace_clock_arm64_cntvct, "cntvct", .in_ns = 0 }, + +#endif /* _ASM_ARM64_TRACE_CLOCK_H */ diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index 88b3e2a21408..ec9180f0ac90 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -29,7 +29,7 @@ obj-y := debug-monitors.o entry.o irq.o fpsimd.o \ cpufeature.o alternative.o cacheinfo.o \ smp.o smp_spin_table.o topology.o smccc-call.o \ syscall.o proton-pack.o idreg-override.o idle.o \ - patching.o + patching.o trace_clock.o targets += efi-entry.o diff --git a/arch/arm64/kernel/trace_clock.c b/arch/arm64/kernel/trace_clock.c new file mode 100644 index 000000000000..fe1315f368cb --- /dev/null +++ b/arch/arm64/kernel/trace_clock.c @@ -0,0 +1,12 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * arm64 trace clocks + */ +#include <asm/trace_clock.h> + +#include <clocksource/arm_arch_timer.h> + +u64 notrace trace_clock_arm64_cntvct(void) +{ + return arch_timer_read_counter(); +} -- 2.33.1 _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
