linux-kernel - Re: [PATCH RFC v3 1/6] cxl/trace: Remove uuid from event trace known events

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Message-ID: <20231103142756.00000e20@Huawei.com>
Date:   Fri, 3 Nov 2023 14:27:56 +0000
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Ira Weiny <ira.weiny@...el.com>
CC:     Dan Williams <dan.j.williams@...el.com>,
        Smita Koralahalli <Smita.KoralahalliChannabasappa@....com>,
        Yazen Ghannam <yazen.ghannam@....com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Dave Jiang <dave.jiang@...el.com>,
        Alison Schofield <alison.schofield@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Ard Biesheuvel <ardb@...nel.org>, <linux-efi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
        <shiju.jose@...wei.com>
Subject: Re: [PATCH RFC v3 1/6] cxl/trace: Remove uuid from event trace
 known events

On Wed, 01 Nov 2023 14:11:18 -0700
Ira Weiny <ira.weiny@...el.com> wrote:

> The uuid printed in the well known events is redundant.  The uuid
> defines what the event was.
> 
> Remove the uuid from the known events and only report it in the generic
> event as it remains informative there.
> 
> Reviewed-by: Davidlohr Bueso <dave@...olabs.net>
> Reviewed-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>

Removing the print is fine, but look like this also removes the actual trace point
field.  That's userspace ABI.  Expanding it is fine, but taking fields away
is more problematic.

Are we sure we don't break anyone?  Shiju, will rasdaemon be fine with this
change?

Thanks,

Jonathan



> ---
>  drivers/cxl/core/trace.h | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/cxl/core/trace.h b/drivers/cxl/core/trace.h
> index a0b5819bc70b..79ed03637604 100644
> --- a/drivers/cxl/core/trace.h
> +++ b/drivers/cxl/core/trace.h
> @@ -189,7 +189,6 @@ TRACE_EVENT(cxl_overflow,
>  	__string(memdev, dev_name(&cxlmd->dev))			\
>  	__string(host, dev_name(cxlmd->dev.parent))		\
>  	__field(int, log)					\
> -	__field_struct(uuid_t, hdr_uuid)			\
>  	__field(u64, serial)					\
>  	__field(u32, hdr_flags)					\
>  	__field(u16, hdr_handle)				\
> @@ -203,7 +202,6 @@ TRACE_EVENT(cxl_overflow,
>  	__assign_str(host, dev_name((cxlmd)->dev.parent));			\
>  	__entry->log = (l);							\
>  	__entry->serial = (cxlmd)->cxlds->serial;				\
> -	memcpy(&__entry->hdr_uuid, &(hdr).id, sizeof(uuid_t));			\
>  	__entry->hdr_length = (hdr).length;					\
>  	__entry->hdr_flags = get_unaligned_le24((hdr).flags);			\
>  	__entry->hdr_handle = le16_to_cpu((hdr).handle);			\
> @@ -212,12 +210,12 @@ TRACE_EVENT(cxl_overflow,
>  	__entry->hdr_maint_op_class = (hdr).maint_op_class
>  
>  #define CXL_EVT_TP_printk(fmt, ...) \
> -	TP_printk("memdev=%s host=%s serial=%lld log=%s : time=%llu uuid=%pUb "	\
> +	TP_printk("memdev=%s host=%s serial=%lld log=%s : time=%llu "		\
>  		"len=%d flags='%s' handle=%x related_handle=%x "		\
>  		"maint_op_class=%u : " fmt,					\
>  		__get_str(memdev), __get_str(host), __entry->serial,		\
>  		cxl_event_log_type_str(__entry->log),				\
> -		__entry->hdr_timestamp, &__entry->hdr_uuid, __entry->hdr_length,\
> +		__entry->hdr_timestamp, __entry->hdr_length,			\
>  		show_hdr_flags(__entry->hdr_flags), __entry->hdr_handle,	\
>  		__entry->hdr_related_handle, __entry->hdr_maint_op_class,	\
>  		##__VA_ARGS__)
> @@ -231,15 +229,17 @@ TRACE_EVENT(cxl_generic_event,
>  
>  	TP_STRUCT__entry(
>  		CXL_EVT_TP_entry
> +		__field_struct(uuid_t, hdr_uuid)
>  		__array(u8, data, CXL_EVENT_RECORD_DATA_LENGTH)
>  	),
>  
>  	TP_fast_assign(
>  		CXL_EVT_TP_fast_assign(cxlmd, log, rec->hdr);
> +		memcpy(&__entry->hdr_uuid, &rec->hdr.id, sizeof(uuid_t));
>  		memcpy(__entry->data, &rec->data, CXL_EVENT_RECORD_DATA_LENGTH);
>  	),
>  
> -	CXL_EVT_TP_printk("%s",
> +	CXL_EVT_TP_printk("uuid=%pUb %s", &__entry->hdr_uuid,
>  		__print_hex(__entry->data, CXL_EVENT_RECORD_DATA_LENGTH))
>  );
>  
>