Re: [PATCH 1/2] RISCV: KVM: add tracepoints for entry and exit events

Anup Patel
2024-04-08T12:07:50Z

On Thu, Mar 28, 2024 at 8:49 AM Shenlin Liang
<liangshenlin@eswincomputing.com> wrote:
>
> Like other architectures, RISCV KVM also needs to add these event
> tracepoints to count the number of times kvm guest entry/exit.
>
> Signed-off-by: Shenlin Liang <liangshenlin@eswincomputing.com>
> ---
> arch/riscv/kvm/trace_riscv.h | 60 ++++++++++++++++++++++++++++++++++++
> arch/riscv/kvm/vcpu.c | 7 +++++
> 2 files changed, 67 insertions(+)
> create mode 100644 arch/riscv/kvm/trace_riscv.h
>
> diff --git a/arch/riscv/kvm/trace_riscv.h b/arch/riscv/kvm/trace_riscv.h
> new file mode 100644
> index 000000000000..5848083c7a5e
> --- /dev/null
> +++ b/arch/riscv/kvm/trace_riscv.h
> @@ -0,0 +1,60 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Tracepoints for RISC-V KVM
> + *
> + * Copyright 2024 Beijing ESWIN Computing Technology Co., Ltd.
> + *
> + */
> +#if !defined(_TRACE_RSICV_KVM_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_RSICV_KVM_H

s/_RSICV_/_RISCV_/

> +
> +#include <linux/tracepoint.h>
> +
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM kvm
> +
> +TRACE_EVENT(kvm_entry,
> + TP_PROTO(struct kvm_vcpu *vcpu),
> + TP_ARGS(vcpu),
> +
> + TP_STRUCT__entry(
> + __field(unsigned long, pc)
> + ),
> +
> + TP_fast_assign(
> + __entry->pc = vcpu->arch.guest_context.sepc;
> + ),
> +
> + TP_printk("PC: 0x%016lx", __entry->pc)
> +);
> +
> +TRACE_EVENT(kvm_exit,
> + TP_PROTO(struct kvm_vcpu *vcpu, unsigned long exit_reason,
> + unsigned long scause),
> + TP_ARGS(vcpu, exit_reason, scause),
> +
> + TP_STRUCT__entry(
> + __field(unsigned long, pc)
> + __field(unsigned long, exit_reason)
> + __field(unsigned long, scause)

This is not the right contents describing a KVM exit.

The fields over here should be aligned with "struct kvm_cpu_trap"
so we should have following fields:
__field(unsigned long, sepc)
__field(unsigned long, scause)
__field(unsigned long, stval)
__field(unsigned long, htval)
__field(unsigned long, htinst)

> + ),
> +
> + TP_fast_assign(
> + __entry->pc = vcpu->arch.guest_context.sepc;
> + __entry->exit_reason = exit_reason;
> + __entry->scause = scause;
> + ),
> +
> + TP_printk("EXIT_REASON:0x%lx,PC: 0x%016lx,SCAUSE:0x%lx",
> + __entry->exit_reason, __entry->pc, __entry->scause)
> +);
> +
> +#endif /* _TRACE_RSICV_KVM_H */
> +
> +#undef TRACE_INCLUDE_PATH
> +#define TRACE_INCLUDE_PATH .
> +#undef TRACE_INCLUDE_FILE
> +#define TRACE_INCLUDE_FILE trace_riscv
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index b5ca9f2e98ac..ed0932f0d514 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -21,6 +21,9 @@
> #include <asm/cacheflush.h>
> #include <asm/kvm_vcpu_vector.h>
>
> +#define CREATE_TRACE_POINTS
> +#include "trace_riscv.h"
> +
> const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
> KVM_GENERIC_VCPU_STATS(),
> STATS_DESC_COUNTER(VCPU, ecall_exit_stat),
> @@ -782,6 +785,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> */
> kvm_riscv_local_tlb_sanitize(vcpu);
>
> + trace_kvm_entry(vcpu);
> +
> guest_timing_enter_irqoff();
>
> kvm_riscv_vcpu_enter_exit(vcpu);
> @@ -820,6 +825,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
>
> local_irq_enable();
>
> + trace_kvm_exit(vcpu, run->exit_reason, trap.scause);
> +
> preempt_enable();
>
> kvm_vcpu_srcu_read_lock(vcpu);
> --
> 2.37.2
>

Regards,
Anup