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Date: Thu, 25 Aug 2022 11:46:32 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: <ira.weiny@...el.com>
CC: Dan Williams <dan.j.williams@...el.com>,
Alison Schofield <alison.schofield@...el.com>,
Vishal Verma <vishal.l.verma@...el.com>,
"Ben Widawsky" <bwidawsk@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>,
Davidlohr Bueso <dave@...olabs.net>,
<linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>
Subject: Re: [RFC PATCH 5/9] cxl/mem: Trace DRAM Event Record
On Fri, 12 Aug 2022 22:32:39 -0700
ira.weiny@...el.com wrote:
> From: Ira Weiny <ira.weiny@...el.com>
>
> CXL v3.0 section 8.2.9.2.1.2 defines the DRAM Event Record.
>
> Determine if the event read is a DRAM event record and if so trace the
> record.
>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
>
> ---
> This record has a very odd byte layout with 2 - 16 bit fields
> (validity_flags and column) aligned on an odd byte boundary. In
> addition nibble_mask and row are oddly aligned.
>
> I've made my best guess as to how the endianess of these fields should
> be resolved. But I'm happy to hear from other folks if what I have is
> wrong.
My assumption is same as you. We should sanity check of course by
poking relevant people.
Similar comments in here to previous. Use the get_unaligned_le24()
accessors + consider not printing invalid fields.
>
> struct cxl_evt_dram_rec {
> struct cxl_event_record_hdr hdr;
> __le64 phys_addr;
> u8 descriptor;
> u8 type;
> u8 transaction_type;
> u16 validity_flags;
> u8 channel;
> u8 rank;
> u8 nibble_mask[CXL_EVT_DER_NIBBLE_MASK_SIZE];
> u8 bank_group;
> u8 bank;
> u8 row[CXL_EVT_DER_ROW_SIZE];
> u16 column;
> u8 correction_mask[CXL_EVT_DER_CORRECTION_MASK_SIZE];
> } __packed;
> ---
> drivers/cxl/core/mbox.c | 16 +++++
> drivers/cxl/cxlmem.h | 24 +++++++
> include/trace/events/cxl-events.h | 114 ++++++++++++++++++++++++++++++
> 3 files changed, 154 insertions(+)
>
> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> index 0e433f072163..6414588a3c7b 100644
> --- a/drivers/cxl/core/mbox.c
> +++ b/drivers/cxl/core/mbox.c
> @@ -717,6 +717,14 @@ static const uuid_t gen_media_event_uuid =
> UUID_INIT(0xfbcd0a77, 0xc260, 0x417f,
> 0x85, 0xa9, 0x08, 0x8b, 0x16, 0x21, 0xeb, 0xa6);
>
> +/*
> + * DRAM Event Record
> + * CXL v3.0 section 8.2.9.2.1.2; Table 8-44
rev3.0, r3.0 or just 3.0
> + */
> +static const uuid_t dram_event_uuid =
> + UUID_INIT(0x601dcbb3, 0x9c06, 0x4eab,
> + 0xb8, 0xaf, 0x4e, 0x9b, 0xfb, 0x5c, 0x96, 0x24);
> +
> static void cxl_trace_event_record(const char *dev_name,
> enum cxl_event_log_type type,
> struct cxl_get_event_payload *payload)
> @@ -731,6 +739,14 @@ static void cxl_trace_event_record(const char *dev_name,
> return;
> }
>
> + if (uuid_equal(id, &dram_event_uuid)) {
Why not else if? Should be obvious to compiler that multiple uuid_equal
conditions can't match, but even better to not make it try hard perhaps?
> + struct cxl_evt_dram_rec *rec =
> + (struct cxl_evt_dram_rec *)&payload->record;
> +
> + trace_cxl_dram_event(dev_name, type, rec);
> + return;
> + }
> +
> /* For unknown record types print just the header */
> trace_cxl_event(dev_name, type, &payload->record);
> }
> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> index 33669459ae4b..50536c0a7850 100644
> --- a/drivers/cxl/cxlmem.h
> +++ b/drivers/cxl/cxlmem.h
> @@ -421,6 +421,30 @@ struct cxl_evt_gen_media {
> u8 component_id[CXL_EVT_GEN_MED_COMP_ID_SIZE];
> } __packed;
>
> +/*
> + * DRAM Event Record - DER
> + * CXL v3.0 section 8.2.9.2.1.2; Table 3-44
> + */
> +#define CXL_EVT_DER_NIBBLE_MASK_SIZE 3
> +#define CXL_EVT_DER_ROW_SIZE 3
> +#define CXL_EVT_DER_CORRECTION_MASK_SIZE 0x20
> +struct cxl_evt_dram_rec {
> + struct cxl_event_record_hdr hdr;
> + __le64 phys_addr;
> + u8 descriptor;
> + u8 type;
> + u8 transaction_type;
> + u16 validity_flags;
I've not tried it, but can we just mark these as __le16 and use
the unaligned accessors? get_unaligned_le16 etc
Also there is get_unaligned_le24() for the 3 byte ones.
> + u8 channel;
> + u8 rank;
> + u8 nibble_mask[CXL_EVT_DER_NIBBLE_MASK_SIZE];
> + u8 bank_group;
> + u8 bank;
> + u8 row[CXL_EVT_DER_ROW_SIZE];
> + u16 column;
> + u8 correction_mask[CXL_EVT_DER_CORRECTION_MASK_SIZE];
> +} __packed;
> +
> struct cxl_mbox_get_partition_info {
> __le64 active_volatile_cap;
> __le64 active_persistent_cap;
> diff --git a/include/trace/events/cxl-events.h b/include/trace/events/cxl-events.h
> index b51c51fd4e62..db9b34ddd240 100644
> --- a/include/trace/events/cxl-events.h
> +++ b/include/trace/events/cxl-events.h
> @@ -244,6 +244,120 @@ TRACE_EVENT(cxl_gen_media_event,
> )
> );
>
> +/*
> + * DRAM Event Record - DER
> + *
> + * CXL v2.0 section 8.2.9.1.1.2; Table 155
> + */
> +/*
> + * DRAM Event Record defines many fields the same as the General Media Event
> + * Record. Reuse those definitions as appropriate.
> + */
> +#define CXL_DER_VALID_CHANNEL BIT(0)
> +#define CXL_DER_VALID_RANK BIT(1)
> +#define CXL_DER_VALID_NIBBLE BIT(2)
> +#define CXL_DER_VALID_BANK_GROUP BIT(3)
> +#define CXL_DER_VALID_BANK BIT(4)
> +#define CXL_DER_VALID_ROW BIT(5)
> +#define CXL_DER_VALID_COLUMN BIT(6)
> +#define CXL_DER_VALID_CORRECTION_MASK BIT(7)
> +#define show_dram_valid_flags(flags) __print_flags(flags, "|", \
> + { CXL_DER_VALID_CHANNEL, "CHANNEL" }, \
> + { CXL_DER_VALID_RANK, "RANK" }, \
> + { CXL_DER_VALID_NIBBLE, "NIBBLE" }, \
> + { CXL_DER_VALID_BANK_GROUP, "BANK GROUP" }, \
> + { CXL_DER_VALID_BANK, "BANK" }, \
> + { CXL_DER_VALID_ROW, "ROW" }, \
> + { CXL_DER_VALID_COLUMN, "COLUMN" }, \
> + { CXL_DER_VALID_CORRECTION_MASK, "CORRECTION MASK" } \
> +)
> +
> +TRACE_EVENT(cxl_dram_event,
> +
> + TP_PROTO(const char *dev_name, enum cxl_event_log_type log,
> + struct cxl_evt_dram_rec *rec),
> +
> + TP_ARGS(dev_name, log, rec),
> +
> + TP_STRUCT__entry(
> + /* Common */
> + __string(dev_name, dev_name)
> + __field(int, log)
> + __array(u8, id, UUID_SIZE)
> + __field(u32, flags)
> + __field(u16, handle)
> + __field(u16, related_handle)
> + __field(u64, timestamp)
> +
> + /* DRAM */
> + __field(u64, phys_addr)
> + __field(u8, descriptor)
> + __field(u8, type)
> + __field(u8, transaction_type)
> + __field(u8, channel)
> + __field(u16, validity_flags)
> + __field(u16, column) /* Out of order to pack trace record */
> + __field(u32, nibble_mask)
> + __field(u32, row)
> + __array(u8, cor_mask, CXL_EVT_DER_CORRECTION_MASK_SIZE)
> + __field(u8, rank) /* Out of order to pack trace record */
> + __field(u8, bank_group) /* Out of order to pack trace record */
> + __field(u8, bank) /* Out of order to pack trace record */
> + ),
> +
> + TP_fast_assign(
> + /* Common */
> + __assign_str(dev_name, dev_name);
> + memcpy(__entry->id, &rec->hdr.id, UUID_SIZE);
> + __entry->log = log;
> + __entry->flags = le32_to_cpu(rec->hdr.flags_length) >> 8;
> + __entry->handle = le16_to_cpu(rec->hdr.handle);
> + __entry->related_handle = le16_to_cpu(rec->hdr.related_handle);
> + __entry->timestamp = le64_to_cpu(rec->hdr.timestamp);
> +
> + /* DRAM */
> + __entry->phys_addr = le64_to_cpu(rec->phys_addr);
> + __entry->descriptor = rec->descriptor;
> + __entry->type = rec->type;
> + __entry->transaction_type = rec->transaction_type;
> + __entry->validity_flags = le16_to_cpu(rec->validity_flags);
> + __entry->channel = rec->channel;
> + __entry->rank = rec->rank;
> + __entry->nibble_mask = rec->nibble_mask[0] << 24 |
> + rec->nibble_mask[1] << 16 |
> + rec->nibble_mask[2] << 8; /* 3 byte LE ? */
Use get_unalinged_le24() ? I'd definitely expect these to be le24.
> + __entry->nibble_mask = le32_to_cpu(__entry->nibble_mask);
That doesn't look right. You will have unwound the endianness using
the shifts above. Don't convert it again (noop on le systems, so you
probably won't see a problem when testing).
> + __entry->bank_group = rec->bank_group;
> + __entry->bank = rec->bank;
> + __entry->row = rec->row[0] << 24 |
> + rec->row[1] << 16 |
> + rec->row[2] << 8; /* 3 byte LE ? */
get_unaligned_le24()
> + __entry->row = le32_to_cpu(__entry->row);
> + __entry->column = le16_to_cpu(rec->column);
> + memcpy(__entry->cor_mask, &rec->correction_mask,
> + CXL_EVT_DER_CORRECTION_MASK_SIZE);
> + ),
> +
> + TP_printk("%s: %s time=%llu id=%pUl handle=%x related_handle=%x hdr_flags='%s': " \
> + "phys_addr=%llx volatile=%s desc='%s' type='%s' trans_type='%s' channel=%u " \
> + "rank=%u nibble_mask=%x bank_group=%u bank=%u row=%u column=%u " \
> + "cor_mask=%s valid_flags='%s'",
> + __get_str(dev_name), show_log_type(__entry->log),
> + __entry->timestamp, __entry->id, __entry->handle,
> + __entry->related_handle, show_hdr_flags(__entry->flags),
> + __entry->phys_addr & ~CXL_GMER_PHYS_ADDR_MASK,
> + (__entry->phys_addr & CXL_GMER_PHYS_ADDR_VOLATILE) ? "TRUE" : "FALSE",
> + show_event_desc_flags(__entry->descriptor),
As before can we not print the invalid ones based on the validity flags?
Few years ago now, but I did something along those lines for the CCIX equivalent of
this stuff. (honestly can't remember much about it now though!)
Was a bit fiddly but lead to nicer prints in my opinion.
https://lore.kernel.org/all/20191114133919.32290-2-Jonathan.Cameron@huawei.com/
> + show_mem_event_type(__entry->type),
> + show_trans_type(__entry->transaction_type),
> + __entry->channel, __entry->rank, __entry->nibble_mask,
> + __entry->bank_group, __entry->bank,
> + __entry->row, __entry->column,
> + __print_hex(__entry->cor_mask, CXL_EVT_DER_CORRECTION_MASK_SIZE),
> + show_dram_valid_flags(__entry->validity_flags)
> + )
> +);
> +
> #endif /* _CXL_TRACE_EVENTS_H */
>
> /* This part must be outside protection */
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