From:   Rakesh Babu Saladi <rsaladi2@marvell.com>
To:     Mark Rutland <mark.rutland@arm.com>
CC:     "lpieralisi@kernel.org" <lpieralisi@kernel.org>,
        "sudeep.holla@arm.com" <sudeep.holla@arm.com>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Sunil Kovvuri Goutham <sgoutham@marvell.com>,
        George Cherian <gcherian@marvell.com>,
        Naveen Mamindlapalli <naveenm@marvell.com>
Subject: RE: [EXT] Re: [PATCH] arm64: smccc: Add trace events to SMC calls.
Thread-Topic: [EXT] Re: [PATCH] arm64: smccc: Add trace events to SMC calls.
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Date:   Wed, 8 Mar 2023 12:25:15 +0000
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Hi Mark,=20

Please see comments in line.

Thanks,
Rakesh.

-----Original Message-----
From: Mark Rutland <mark.rutland@arm.com>=20
Sent: Monday, March 6, 2023 8:18 PM
To: Rakesh Babu Saladi <rsaladi2@marvell.com>
Cc: lpieralisi@kernel.org; sudeep.holla@arm.com; linux-arm-kernel@lists.inf=
radead.org; linux-kernel@vger.kernel.org; Sunil Kovvuri Goutham <sgoutham@m=
arvell.com>; George Cherian <gcherian@marvell.com>; Naveen Mamindlapalli <n=
aveenm@marvell.com>
Subject: [EXT] Re: [PATCH] arm64: smccc: Add trace events to SMC calls.

External Email

----------------------------------------------------------------------
On Sat, Mar 04, 2023 at 06:28:50PM +0530, Rakesh Babu Saladi wrote:
> This patch adds start and end trace events to an SMC call sent from=20
> kernel to ATF. The start trace event prints the smc_id and the end=20
> trace event prints the smc_id and the time taken to process the SMC=20
> call.
>=20
> Signed-off-by: Rakesh Babu Saladi <rsaladi2@marvell.com>

We've said no to this in the past:

  https://urldefense.proofpoint.com/v2/url?u=3Dhttps-3A__lore.kernel.org_lk=
ml_20210923112058.GA14893-40C02TD0UTHF1T.local_&d=3DDwIBAg&c=3DnKjWec2b6R0m=
OyPaz7xtfQ&r=3DOrNjoyjPmqlDfiSr6RMDtAJU4gxiGfgzEtgbqDmoQPA&m=3Dfj6aQCqc0xOY=
gRMw7BGCVRrOEabi2taRuKl63gCdHras-JfpWCGhjp6HqaLZYj9I&s=3D1_EJt65j5EoyHhcroJ=
xJFMIkTqQY6jKtWypPIzmgYK8&e=3D=20

I don't think anything has changed, and this has all the same problems as b=
efore, so I do not think we should do this.
Rakesh >> Can you please be more specific why the changes are not getting a=
ccepted?

Which SMC calls do you want to trace, and why?
Rakesh >> These traces we would like to have for debugging purposes while c=
alling any SMC call.

Thanks,
Mark.

> ---
>  drivers/firmware/smccc/Makefile      |  3 +-
>  drivers/firmware/smccc/smccc.c       | 14 ++++++++++
>  drivers/firmware/smccc/smccc_trace.c |  7 +++++ =20
> drivers/firmware/smccc/smccc_trace.h | 41 ++++++++++++++++++++++++++++
>  include/linux/arm-smccc.h            |  4 ++-
>  kernel/time/timekeeping.c            |  7 +++++
>  6 files changed, 74 insertions(+), 2 deletions(-)  create mode 100644=20
> drivers/firmware/smccc/smccc_trace.c
>  create mode 100644 drivers/firmware/smccc/smccc_trace.h
>=20
> diff --git a/drivers/firmware/smccc/Makefile=20
> b/drivers/firmware/smccc/Makefile index 40d19144a860..e74c35191b49=20
> 100644
> --- a/drivers/firmware/smccc/Makefile
> +++ b/drivers/firmware/smccc/Makefile
> @@ -1,4 +1,5 @@
>  # SPDX-License-Identifier: GPL-2.0
>  #
> -obj-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY)	+=3D smccc.o kvm_guest.o
> +ccflags-y +=3D -I$(src)
> +obj-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY)	+=3D smccc_trace.o smccc.o kvm_gu=
est.o
>  obj-$(CONFIG_ARM_SMCCC_SOC_ID)	+=3D soc_id.o
> diff --git a/drivers/firmware/smccc/smccc.c=20
> b/drivers/firmware/smccc/smccc.c index 60ccf3e90d7d..7631a16479e9=20
> 100644
> --- a/drivers/firmware/smccc/smccc.c
> +++ b/drivers/firmware/smccc/smccc.c
> @@ -11,6 +11,7 @@
>  #include <linux/kernel.h>
>  #include <linux/platform_device.h>
>  #include <asm/archrandom.h>
> +#include "smccc_trace.h"
> =20
>  static u32 smccc_version =3D ARM_SMCCC_VERSION_1_0;  static enum=20
> arm_smccc_conduit smccc_conduit =3D SMCCC_CONDUIT_NONE; @@ -59,3 +60,16=20
> @@ static int __init smccc_devices_init(void)
>  	return 0;
>  }
>  device_initcall(smccc_devices_init);
> +
> +void arm_smccc_smc(unsigned long a0, unsigned long a1, unsigned long a2,=
 unsigned long a3,
> +		   unsigned long a4, unsigned long a5, unsigned long a6, unsigned long=
 a7,
> +		   struct arm_smccc_res *res)
> +{
> +	u64 start, elapsed;
> +
> +	trace_arm_smccc_smc_start(a0);
> +	start =3D ktime_get_ns();
> +	__arm_smccc_smc(a0, a1, a2, a3, a4, a5, a6, a7, res, NULL);
> +	elapsed =3D ktime_get_ns() - start;
> +	trace_arm_smccc_smc_end(a0, elapsed); }
> diff --git a/drivers/firmware/smccc/smccc_trace.c=20
> b/drivers/firmware/smccc/smccc_trace.c
> new file mode 100644
> index 000000000000..6b94d5d9c0f4
> --- /dev/null
> +++ b/drivers/firmware/smccc/smccc_trace.c
> @@ -0,0 +1,7 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#define CREATE_TRACE_POINTS
> +#include "smccc_trace.h"
> +
> +EXPORT_TRACEPOINT_SYMBOL(arm_smccc_smc_start);
> +EXPORT_TRACEPOINT_SYMBOL(arm_smccc_smc_end);
> diff --git a/drivers/firmware/smccc/smccc_trace.h=20
> b/drivers/firmware/smccc/smccc_trace.h
> new file mode 100644
> index 000000000000..c0ef836bc093
> --- /dev/null
> +++ b/drivers/firmware/smccc/smccc_trace.h
> @@ -0,0 +1,41 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM smccc
> +
> +#if !defined(__SMCCC_TRACE_H) || defined(TRACE_HEADER_MULTI_READ)=20
> +#define __SMCCC_TRACE_H
> +
> +#include <linux/types.h>
> +#include <linux/tracepoint.h>
> +
> +TRACE_EVENT(arm_smccc_smc_start,
> +	    TP_PROTO(unsigned long smc_id),
> +	    TP_ARGS(smc_id),
> +	    TP_STRUCT__entry(__field(unsigned long, smc_id)),
> +	    TP_fast_assign(__entry->smc_id =3D smc_id;),
> +	    TP_printk("SMC ID: 0x%lx", __entry->smc_id) );
> +
> +TRACE_EVENT(arm_smccc_smc_end,
> +	    TP_PROTO(unsigned long smc_id, u64 elapsed_time),
> +	    TP_ARGS(smc_id, elapsed_time),
> +	    TP_STRUCT__entry(__field(unsigned long, smc_id)
> +			     __field(u64, elapsed_time)
> +	    ),
> +	    TP_fast_assign(__entry->smc_id =3D smc_id;
> +			   __entry->elapsed_time =3D elapsed_time;
> +	    ),
> +	    TP_printk("SMC ID: 0x%lx time taken to process : %llu ns",
> +		      __entry->smc_id, __entry->elapsed_time) );
> +
> +#endif /* __SMCCC_TRACE_H */
> +
> +#undef TRACE_INCLUDE_PATH
> +#define TRACE_INCLUDE_PATH .
> +
> +#undef TRACE_INCLUDE_FILE
> +#define TRACE_INCLUDE_FILE smccc_trace
> +
> +#include <trace/define_trace.h>
> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h=20
> index 220c8c60e021..39588c3db486 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.h
> @@ -358,7 +358,9 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, uns=
igned long a1,
>  			unsigned long a5, unsigned long a6, unsigned long a7,
>  			struct arm_smccc_res *res, struct arm_smccc_quirk *quirk);
> =20
> -#define arm_smccc_smc(...) __arm_smccc_smc(__VA_ARGS__, NULL)
> +void arm_smccc_smc(unsigned long a0, unsigned long a1, unsigned long a2,
> +		   unsigned long a3, unsigned long a4, unsigned long a5,
> +		   unsigned long a6, unsigned long a7, struct arm_smccc_res *res);
> =20
>  #define arm_smccc_smc_quirk(...) __arm_smccc_smc(__VA_ARGS__)
> =20
> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c=20
> index 5579ead449f2..3a3bf2d674a3 100644
> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -192,6 +192,13 @@ static inline u64 tk_clock_read(const struct=20
> tk_read_base *tkr)  {
>  	struct clocksource *clock =3D READ_ONCE(tkr->clock);
> =20
> +	/* At the time of kernel booting some SMC calls are called before the
> +	 * clock is initialized, in such cases it would lead to kernel crash.
> +	 * To prevent kernel crash in such cases this check is included.
> +	 */
> +	if (unlikely(!clock))
> +		return 0;
> +
>  	return clock->read(clock);
>  }
> =20
> --
> 2.17.1
>=20