Re: [PATCH v8 19/20] virt: geniezone: Add tracing support for hyp call and vcpu exit_reason

[Steven Rostedt]

On Thu, 28 Dec 2023 18:51:46 +0800
Yi-De Wu <yi-de.wu@xxxxxxxxxxxx> wrote:

> Add tracepoints for hypervisor calls and VCPU exit reasons in GenieZone
> driver. It aids performance debugging by providing more information
> about hypervisor operations and VCPU behavior.
> 
> Command Usage:
> echo geniezone:* >> /sys/kernel/tracing/set_event
> echo 1 > /sys/kernel/tracing/tracing_on
> echo 0 > /sys/kernel/tracing/tracing_on
> cat /sys/kernel/tracing/trace
> 
> For example:
> crosvm_vcpu0-4838 [004] ..... 76053.536034: mtk_hypcall_enter: id=0xbb001005
> crosvm_vcpu0-4838 [004] ..... 76053.540039: mtk_hypcall_leave: id=0xbb001005 invalid=0
> crosvm_vcpu0-4838 [004] ..... 76053.540040: mtk_vcpu_exit: vcpu exit_reason=0x92920003

Cleaning out patchwork, I noticed this patch.

You can make the above more informative by having it output:

 crosvm_vcpu0-4838 [004] ..... 76053.540040: mtk_vcpu_exit: vcpu exit_reason=IRQ


> 
> This example tracks a hypervisor function call by an ID (`0xbb001005`)
> from initiation to termination, which is supported (invalid=0). A vCPU
> exit is triggered by an Interrupt Request (IRQ) (exit reason: 0x92920003).
> 
> /* VM exit reason */
> enum {
> 	GZVM_EXIT_UNKNOWN = 0x92920000,
> 	GZVM_EXIT_MMIO = 0x92920001,
> 	GZVM_EXIT_HYPERCALL = 0x92920002,
> 	GZVM_EXIT_IRQ = 0x92920003,
> 	GZVM_EXIT_EXCEPTION = 0x92920004,
> 	GZVM_EXIT_DEBUG = 0x92920005,
> 	GZVM_EXIT_FAIL_ENTRY = 0x92920006,
> 	GZVM_EXIT_INTERNAL_ERROR = 0x92920007,
> 	GZVM_EXIT_SYSTEM_EVENT = 0x92920008,
> 	GZVM_EXIT_SHUTDOWN = 0x92920009,
> 	GZVM_EXIT_GZ = 0x9292000a,
> };
> 
> Signed-off-by: Liju-clr Chen <liju-clr.chen@xxxxxxxxxxxx>
> Signed-off-by: Yi-De Wu <yi-de.wu@xxxxxxxxxxxx>
> ---
>  arch/arm64/geniezone/vm.c          |  5 +++
>  drivers/virt/geniezone/gzvm_vcpu.c |  3 ++
>  include/trace/events/geniezone.h   | 54 ++++++++++++++++++++++++++++++
>  3 files changed, 62 insertions(+)
>  create mode 100644 include/trace/events/geniezone.h
> 
> diff --git a/arch/arm64/geniezone/vm.c b/arch/arm64/geniezone/vm.c
> index a9d264bbb3b1..5667643251b5 100644
> --- a/arch/arm64/geniezone/vm.c
> +++ b/arch/arm64/geniezone/vm.c
> @@ -7,6 +7,8 @@
>  #include <linux/err.h>
>  #include <linux/uaccess.h>
>  
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/geniezone.h>
>  #include <linux/gzvm.h>
>  #include <linux/gzvm_drv.h>
>  #include "gzvm_arch_common.h"
> @@ -33,7 +35,10 @@ int gzvm_hypcall_wrapper(unsigned long a0, unsigned long a1,
>  			 unsigned long a6, unsigned long a7,
>  			 struct arm_smccc_res *res)
>  {
> +	trace_mtk_hypcall_enter(a0);
>  	arm_smccc_hvc(a0, a1, a2, a3, a4, a5, a6, a7, res);
> +	trace_mtk_hypcall_leave(a0, (res->a0 != ERR_NOT_SUPPORTED) ? 0 : 1);
> +
>  	return gzvm_err_to_errno(res->a0);
>  }
>  
> diff --git a/drivers/virt/geniezone/gzvm_vcpu.c b/drivers/virt/geniezone/gzvm_vcpu.c
> index 86c690749277..138ec064596b 100644
> --- a/drivers/virt/geniezone/gzvm_vcpu.c
> +++ b/drivers/virt/geniezone/gzvm_vcpu.c
> @@ -10,6 +10,8 @@
>  #include <linux/mm.h>
>  #include <linux/platform_device.h>
>  #include <linux/slab.h>
> +
> +#include <trace/events/geniezone.h>
>  #include <linux/gzvm_drv.h>
>  
>  /* maximum size needed for holding an integer */
> @@ -103,6 +105,7 @@ static long gzvm_vcpu_run(struct gzvm_vcpu *vcpu, void __user *argp)
>  
>  	while (!need_userspace && !signal_pending(current)) {
>  		gzvm_arch_vcpu_run(vcpu, &exit_reason);
> +		trace_mtk_vcpu_exit(exit_reason);
>  
>  		switch (exit_reason) {
>  		case GZVM_EXIT_MMIO:
> diff --git a/include/trace/events/geniezone.h b/include/trace/events/geniezone.h
> new file mode 100644
> index 000000000000..1fa44f9c4b3c
> --- /dev/null
> +++ b/include/trace/events/geniezone.h
> @@ -0,0 +1,54 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (c) 2023 MediaTek Inc.
> + */
> +
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM geniezone
> +
> +#define _TRACE_GENIEZONE_H
> +
> +#include <linux/tracepoint.h>

#define GZVM_EXIT_REASONS	\
	EM(UNKNOWN)		\
	EM(MMIO)		\
	EM(HYPERCALL)		\
	EM(IRQ)			\
	EM(EXCEPTION)		\
	EM(DEBUG)		\
	EM(FAIL_ENTRY)		\
	EM(INTERNAL_ERROR)	\
	EM(SYSTEM_EVENT)	\
	EM(SHUTDOWN)		\
	EMe(GZ)

#undef EM
#undef EMe
#define EM(a) TRACE_DEFINE_ENUM(GZVM_EXIT_##a);
#define EMe(a) TRACE_DEFINE_ENUM(GZVM_EXIT_##a);

GZVM_EXIT_REASONS

#undef EM
#undef EMe

#define EM(a)       { GZVM_EXIT_##a, #a },
#define EMe(a)      { GZVM_EXIT_##a, #a }

> +
> +TRACE_EVENT(mtk_hypcall_enter,
> +	    TP_PROTO(unsigned long id),
> +
> +	    TP_ARGS(id),
> +
> +	    TP_STRUCT__entry(__field(unsigned long, id)),
> +
> +	    TP_fast_assign(__entry->id = id;),
> +
> +	    TP_printk("id=0x%lx", __entry->id)
> +);
> +
> +TRACE_EVENT(mtk_hypcall_leave,
> +	    TP_PROTO(unsigned long id, unsigned long invalid),
> +
> +	    TP_ARGS(id, invalid),
> +
> +	    TP_STRUCT__entry(__field(unsigned long, id)
> +			     __field(unsigned long, invalid)
> +	    ),
> +
> +	    TP_fast_assign(__entry->id = id;
> +			   __entry->invalid = invalid;
> +	    ),
> +
> +	    TP_printk("id=0x%lx invalid=%lu", __entry->id, __entry->invalid)
> +);
> +
> +TRACE_EVENT(mtk_vcpu_exit,
> +	    TP_PROTO(unsigned long exit_reason),
> +
> +	    TP_ARGS(exit_reason),
> +
> +	    TP_STRUCT__entry(__field(unsigned long, exit_reason)),
> +
> +	    TP_fast_assign(__entry->exit_reason = exit_reason;),
> +
> +	    TP_printk("vcpu exit_reason=0x%lx", __entry->exit_reason)

	    TP_printk("vcpu exit_reason=0x%lx",
		__print_symbolic(__entry->exit_reason, GZVM_EXIT_REASONS))


And instead of having the cryptic enum values printed, you will have human
readable reasons.

-- Steve


> +);
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>