On Wed, Jan 18, 2023 at 1:53 PM Ira Weiny <ira.weiny@xxxxxxxxx> wrote:
>
> CXL devices have multiple event logs which can be queried for CXL event
> records. Devices are required to support the storage of at least one
> event record in each event log type.
>
> Devices track event log overflow by incrementing a counter and tracking
> the time of the first and last overflow event seen.
>
> Software queries events via the Get Event Record mailbox command; CXL
> rev 3.0 section 8.2.9.2.2 and clears events via CXL rev 3.0 section
> 8.2.9.2.3 Clear Event Records mailbox command.
>
> If the result of negotiating CXL Error Reporting Control is OS control,
> read and clear all event logs on driver load.
>
> Ensure a clean slate of events by reading and clearing the events on
> driver load.
>
> The status register is not used because a device may continue to trigger
> events and the only requirement is to empty the log at least once. This
> allows for the required transition from empty to non-empty for interrupt
> generation. Handling of interrupts is in a follow on patch.
>
> The device can return up to 1MB worth of event records per query.
> Allocate a shared large buffer to handle the max number of records based
> on the mailbox payload size.
>
> This patch traces a raw event record and leaves specific event record
> type tracing to subsequent patches. Macros are created to aid in
> tracing the common CXL Event header fields.
>
> Each record is cleared explicitly. A clear all bit is specified but is
> only valid when the log overflows.
>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
>
> ---
> Changes in v7:
> Jonathan
> Picked up Jonathans review
> Shorten dev error line lengths
> Return error from devm_add_action_or_reset
> Jonathan/Dan
> Make struct cxl_mbox_clear_event_payload a dynamic struct
> Clarify meaning of CXL_CLEAR_EVENT_MAX_HANDLES
> Jonathan
> Only allocate buffer if native cxl error is true
> ---
> drivers/cxl/core/mbox.c | 148 +++++++++++++++++++++++++++++++++++++++++++++++
> drivers/cxl/core/trace.h | 120 ++++++++++++++++++++++++++++++++++++++
> drivers/cxl/cxl.h | 12 ++++
> drivers/cxl/cxlmem.h | 79 +++++++++++++++++++++++++
> drivers/cxl/pci.c | 42 ++++++++++++++
> 5 files changed, 401 insertions(+)
>
> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> index b03fba212799..c329c1e67a2c 100644
> --- a/drivers/cxl/core/mbox.c
> +++ b/drivers/cxl/core/mbox.c
> @@ -8,6 +8,7 @@
> #include <cxl.h>
>
> #include "core.h"
> +#include "trace.h"
>
> static bool cxl_raw_allow_all;
>
> @@ -717,6 +718,152 @@ int cxl_enumerate_cmds(struct cxl_dev_state *cxlds)
> }
> EXPORT_SYMBOL_NS_GPL(cxl_enumerate_cmds, CXL);
>
> +static int cxl_clear_event_record(struct cxl_dev_state *cxlds,
> + enum cxl_event_log_type log,
> + struct cxl_get_event_payload *get_pl)
> +{
> + struct cxl_mbox_clear_event_payload *payload;
> + u16 total = le16_to_cpu(get_pl->record_count);
> + u8 max_handles = CXL_CLEAR_EVENT_MAX_HANDLES;
> + size_t pl_size = struct_size(payload, handles, max_handles);
> + struct cxl_mbox_cmd mbox_cmd;
> + u16 cnt;
> + int rc = 0;
> + int i;
> +
> + /* Payload size may limit the max handles */
> + if (pl_size > cxlds->payload_size) {
> + max_handles = (cxlds->payload_size - sizeof(*payload)) /
> + sizeof(__le16);
> + pl_size = struct_size(payload, handles, max_handles);
> + }
> +
> + payload = kvzalloc(pl_size, GFP_KERNEL);
> + if (!payload)
> + return -ENOMEM;
> +
> + *payload = (struct cxl_mbox_clear_event_payload) {
> + .event_log = log,
> + };
> +
> + mbox_cmd = (struct cxl_mbox_cmd) {
> + .opcode = CXL_MBOX_OP_CLEAR_EVENT_RECORD,
> + .payload_in = payload,
> + .size_in = pl_size,
> + };
> +
> + /*
> + * Clear Event Records uses u8 for the handle cnt while Get Event
> + * Record can return up to 0xffff records.
> + */
> + i = 0;
> + for (cnt = 0; cnt < total; cnt++) {
> + payload->handles[i++] = get_pl->records[cnt].hdr.handle;
> + dev_dbg(cxlds->dev, "Event log '%d': Clearing %u\n",
> + log, le16_to_cpu(payload->handles[i]));
> +
> + if (i == max_handles) {
> + payload->nr_recs = i;
> + rc = cxl_internal_send_cmd(cxlds, &mbox_cmd);
> + if (rc)
> + goto free_pl;
> + i = 0;
> + }
> + }
> +
> + /* Clear what is left if any */
> + if (i) {
> + payload->nr_recs = i;
> + mbox_cmd.size_in = struct_size(payload, handles, i);
> + rc = cxl_internal_send_cmd(cxlds, &mbox_cmd);
> + if (rc)
> + goto free_pl;
> + }
> +
> +free_pl:
> + kvfree(payload);
> + return rc;
> +}
> +
> +static void cxl_mem_get_records_log(struct cxl_dev_state *cxlds,
> + enum cxl_event_log_type type)
> +{
> + struct cxl_get_event_payload *payload;
> + struct cxl_mbox_cmd mbox_cmd;
> + u8 log_type = type;
> + u16 nr_rec;
> +
> + mutex_lock(&cxlds->event.log_lock);
> + payload = cxlds->event.buf;
> +
> + mbox_cmd = (struct cxl_mbox_cmd) {
> + .opcode = CXL_MBOX_OP_GET_EVENT_RECORD,
> + .payload_in = &log_type,
> + .size_in = sizeof(log_type),
> + .payload_out = payload,
> + .size_out = cxlds->payload_size,
> + .min_out = struct_size(payload, records, 0),
> + };
> +
> + do {
> + int rc, i;
> +
> + rc = cxl_internal_send_cmd(cxlds, &mbox_cmd);
> + if (rc) {
> + dev_err_ratelimited(cxlds->dev,
> + "Event log '%d': Failed to query event records : %d",
> + type, rc);
> + break;
> + }
> +
> + nr_rec = le16_to_cpu(payload->record_count);
> + if (!nr_rec)
> + break;
> +
> + for (i = 0; i < nr_rec; i++)
> + trace_cxl_generic_event(cxlds->dev, type,
> + &payload->records[i]);
> +
> + if (payload->flags & CXL_GET_EVENT_FLAG_OVERFLOW)
> + trace_cxl_overflow(cxlds->dev, type, payload);
> +
> + rc = cxl_clear_event_record(cxlds, type, payload);
> + if (rc) {
> + dev_err_ratelimited(cxlds->dev,
> + "Event log '%d': Failed to clear events : %d",
> + type, rc);
> + break;
> + }
> + } while (nr_rec);
Should the (payload->flags & CXL_GET_EVENT_FLAG_MORE_RECORDS) be used
instead of (nr_rec) in this while condition? According to the spec,
this bit is used to see if there
are more event records.
> +
> + mutex_unlock(&cxlds->event.log_lock);
> +}
> +
> +/**
> + * cxl_mem_get_event_records - Get Event Records from the device
> + * @cxlds: The device data for the operation
> + *
> + * Retrieve all event records available on the device, report them as trace
> + * events, and clear them.
> + *
> + * See CXL rev 3.0 @8.2.9.2.2 Get Event Records
> + * See CXL rev 3.0 @8.2.9.2.3 Clear Event Records
> + */
> +void cxl_mem_get_event_records(struct cxl_dev_state *cxlds, u32 status)
> +{
> + dev_dbg(cxlds->dev, "Reading event logs: %x\n", status);
> +
> + if (status & CXLDEV_EVENT_STATUS_FATAL)
> + cxl_mem_get_records_log(cxlds, CXL_EVENT_TYPE_FATAL);
> + if (status & CXLDEV_EVENT_STATUS_FAIL)
> + cxl_mem_get_records_log(cxlds, CXL_EVENT_TYPE_FAIL);
> + if (status & CXLDEV_EVENT_STATUS_WARN)
> + cxl_mem_get_records_log(cxlds, CXL_EVENT_TYPE_WARN);
> + if (status & CXLDEV_EVENT_STATUS_INFO)
> + cxl_mem_get_records_log(cxlds, CXL_EVENT_TYPE_INFO);
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_mem_get_event_records, CXL);
> +
> /**
> * cxl_mem_get_partition_info - Get partition info
> * @cxlds: The device data for the operation
> @@ -868,6 +1015,7 @@ struct cxl_dev_state *cxl_dev_state_create(struct device *dev)
> }
>
> mutex_init(&cxlds->mbox_mutex);
> + mutex_init(&cxlds->event.log_lock);
> cxlds->dev = dev;
>
> return cxlds;
> diff --git a/drivers/cxl/core/trace.h b/drivers/cxl/core/trace.h
> index 20ca2fe2ca8e..6898212fcb47 100644
> --- a/drivers/cxl/core/trace.h
> +++ b/drivers/cxl/core/trace.h
> @@ -6,7 +6,9 @@
> #if !defined(_CXL_EVENTS_H) || defined(TRACE_HEADER_MULTI_READ)
> #define _CXL_EVENTS_H
>
> +#include <asm-generic/unaligned.h>
> #include <cxl.h>
> +#include <cxlmem.h>
> #include <linux/tracepoint.h>
>
> #define CXL_RAS_UC_CACHE_DATA_PARITY BIT(0)
> @@ -103,6 +105,124 @@ TRACE_EVENT(cxl_aer_correctable_error,
> )
> );
>
> +#include <linux/tracepoint.h>
> +
> +#define cxl_event_log_type_str(type) \
> + __print_symbolic(type, \
> + { CXL_EVENT_TYPE_INFO, "Informational" }, \
> + { CXL_EVENT_TYPE_WARN, "Warning" }, \
> + { CXL_EVENT_TYPE_FAIL, "Failure" }, \
> + { CXL_EVENT_TYPE_FATAL, "Fatal" })
> +
> +TRACE_EVENT(cxl_overflow,
> +
> + TP_PROTO(const struct device *dev, enum cxl_event_log_type log,
> + struct cxl_get_event_payload *payload),
> +
> + TP_ARGS(dev, log, payload),
> +
> + TP_STRUCT__entry(
> + __string(dev_name, dev_name(dev))
> + __field(int, log)
> + __field(u64, first_ts)
> + __field(u64, last_ts)
> + __field(u16, count)
> + ),
> +
> + TP_fast_assign(
> + __assign_str(dev_name, dev_name(dev));
> + __entry->log = log;
> + __entry->count = le16_to_cpu(payload->overflow_err_count);
> + __entry->first_ts = le64_to_cpu(payload->first_overflow_timestamp);
> + __entry->last_ts = le64_to_cpu(payload->last_overflow_timestamp);
> + ),
> +
> + TP_printk("%s: log=%s : %u records from %llu to %llu",
> + __get_str(dev_name), cxl_event_log_type_str(__entry->log),
> + __entry->count, __entry->first_ts, __entry->last_ts)
> +
> +);
> +
> +/*
> + * Common Event Record Format
> + * CXL 3.0 section 8.2.9.2.1; Table 8-42
> + */
> +#define CXL_EVENT_RECORD_FLAG_PERMANENT BIT(2)
> +#define CXL_EVENT_RECORD_FLAG_MAINT_NEEDED BIT(3)
> +#define CXL_EVENT_RECORD_FLAG_PERF_DEGRADED BIT(4)
> +#define CXL_EVENT_RECORD_FLAG_HW_REPLACE BIT(5)
> +#define show_hdr_flags(flags) __print_flags(flags, " | ", \
> + { CXL_EVENT_RECORD_FLAG_PERMANENT, "PERMANENT_CONDITION" }, \
> + { CXL_EVENT_RECORD_FLAG_MAINT_NEEDED, "MAINTENANCE_NEEDED" }, \
> + { CXL_EVENT_RECORD_FLAG_PERF_DEGRADED, "PERFORMANCE_DEGRADED" }, \
> + { CXL_EVENT_RECORD_FLAG_HW_REPLACE, "HARDWARE_REPLACEMENT_NEEDED" } \
> +)
> +
> +/*
> + * Define macros for the common header of each CXL event.
> + *
> + * Tracepoints using these macros must do 3 things:
> + *
> + * 1) Add CXL_EVT_TP_entry to TP_STRUCT__entry
> + * 2) Use CXL_EVT_TP_fast_assign within TP_fast_assign;
> + * pass the dev, log, and CXL event header
> + * 3) Use CXL_EVT_TP_printk() instead of TP_printk()
> + *
> + * See the generic_event tracepoint as an example.
> + */
> +#define CXL_EVT_TP_entry \
> + __string(dev_name, dev_name(dev)) \
> + __field(int, log) \
> + __field_struct(uuid_t, hdr_uuid) \
> + __field(u32, hdr_flags) \
> + __field(u16, hdr_handle) \
> + __field(u16, hdr_related_handle) \
> + __field(u64, hdr_timestamp) \
> + __field(u8, hdr_length) \
> + __field(u8, hdr_maint_op_class)
> +
> +#define CXL_EVT_TP_fast_assign(dev, l, hdr) \
> + __assign_str(dev_name, dev_name(dev)); \
> + __entry->log = (l); \
> + 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); \
> + __entry->hdr_related_handle = le16_to_cpu((hdr).related_handle); \
> + __entry->hdr_timestamp = le64_to_cpu((hdr).timestamp); \
> + __entry->hdr_maint_op_class = (hdr).maint_op_class
> +
> +#define CXL_EVT_TP_printk(fmt, ...) \
> + TP_printk("%s log=%s : time=%llu uuid=%pUb len=%d flags='%s' " \
> + "handle=%x related_handle=%x maint_op_class=%u" \
> + " : " fmt, \
> + __get_str(dev_name), cxl_event_log_type_str(__entry->log), \
> + __entry->hdr_timestamp, &__entry->hdr_uuid, __entry->hdr_length,\
> + show_hdr_flags(__entry->hdr_flags), __entry->hdr_handle, \
> + __entry->hdr_related_handle, __entry->hdr_maint_op_class, \
> + ##__VA_ARGS__)
> +
> +TRACE_EVENT(cxl_generic_event,
> +
> + TP_PROTO(const struct device *dev, enum cxl_event_log_type log,
> + struct cxl_event_record_raw *rec),
> +
> + TP_ARGS(dev, log, rec),
> +
> + TP_STRUCT__entry(
> + CXL_EVT_TP_entry
> + __array(u8, data, CXL_EVENT_RECORD_DATA_LENGTH)
> + ),
> +
> + TP_fast_assign(
> + CXL_EVT_TP_fast_assign(dev, log, rec->hdr);
> + memcpy(__entry->data, &rec->data, CXL_EVENT_RECORD_DATA_LENGTH);
> + ),
> +
> + CXL_EVT_TP_printk("%s",
> + __print_hex(__entry->data, CXL_EVENT_RECORD_DATA_LENGTH))
> +);
> +
> #endif /* _CXL_EVENTS_H */
>
> #define TRACE_INCLUDE_FILE trace
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index aa3af3bb73b2..5974d1082210 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -156,6 +156,18 @@ static inline int ways_to_eiw(unsigned int ways, u8 *eiw)
> #define CXLDEV_CAP_CAP_ID_SECONDARY_MAILBOX 0x3
> #define CXLDEV_CAP_CAP_ID_MEMDEV 0x4000
>
> +/* CXL 3.0 8.2.8.3.1 Event Status Register */
> +#define CXLDEV_DEV_EVENT_STATUS_OFFSET 0x00
> +#define CXLDEV_EVENT_STATUS_INFO BIT(0)
> +#define CXLDEV_EVENT_STATUS_WARN BIT(1)
> +#define CXLDEV_EVENT_STATUS_FAIL BIT(2)
> +#define CXLDEV_EVENT_STATUS_FATAL BIT(3)
> +
> +#define CXLDEV_EVENT_STATUS_ALL (CXLDEV_EVENT_STATUS_INFO | \
> + CXLDEV_EVENT_STATUS_WARN | \
> + CXLDEV_EVENT_STATUS_FAIL | \
> + CXLDEV_EVENT_STATUS_FATAL)
> +
> /* CXL 2.0 8.2.8.4 Mailbox Registers */
> #define CXLDEV_MBOX_CAPS_OFFSET 0x00
> #define CXLDEV_MBOX_CAP_PAYLOAD_SIZE_MASK GENMASK(4, 0)
> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> index ab138004f644..0f272206e294 100644
> --- a/drivers/cxl/cxlmem.h
> +++ b/drivers/cxl/cxlmem.h
> @@ -4,6 +4,7 @@
> #define __CXL_MEM_H__
> #include <uapi/linux/cxl_mem.h>
> #include <linux/cdev.h>
> +#include <linux/uuid.h>
> #include "cxl.h"
>
> /* CXL 2.0 8.2.8.5.1.1 Memory Device Status Register */
> @@ -193,6 +194,17 @@ struct cxl_endpoint_dvsec_info {
> struct range dvsec_range[2];
> };
>
> +/**
> + * struct cxl_event_state - Event log driver state
> + *
> + * @event_buf: Buffer to receive event data
> + * @event_log_lock: Serialize event_buf and log use
> + */
> +struct cxl_event_state {
> + struct cxl_get_event_payload *buf;
> + struct mutex log_lock;
> +};
> +
> /**
> * struct cxl_dev_state - The driver device state
> *
> @@ -266,12 +278,16 @@ struct cxl_dev_state {
>
> struct xarray doe_mbs;
>
> + struct cxl_event_state event;
> +
> int (*mbox_send)(struct cxl_dev_state *cxlds, struct cxl_mbox_cmd *cmd);
> };
>
> enum cxl_opcode {
> CXL_MBOX_OP_INVALID = 0x0000,
> CXL_MBOX_OP_RAW = CXL_MBOX_OP_INVALID,
> + CXL_MBOX_OP_GET_EVENT_RECORD = 0x0100,
> + CXL_MBOX_OP_CLEAR_EVENT_RECORD = 0x0101,
> CXL_MBOX_OP_GET_FW_INFO = 0x0200,
> CXL_MBOX_OP_ACTIVATE_FW = 0x0202,
> CXL_MBOX_OP_GET_SUPPORTED_LOGS = 0x0400,
> @@ -347,6 +363,68 @@ struct cxl_mbox_identify {
> u8 qos_telemetry_caps;
> } __packed;
>
> +/*
> + * Common Event Record Format
> + * CXL rev 3.0 section 8.2.9.2.1; Table 8-42
> + */
> +struct cxl_event_record_hdr {
> + uuid_t id;
> + u8 length;
> + u8 flags[3];
> + __le16 handle;
> + __le16 related_handle;
> + __le64 timestamp;
> + u8 maint_op_class;
> + u8 reserved[15];
> +} __packed;
> +
> +#define CXL_EVENT_RECORD_DATA_LENGTH 0x50
> +struct cxl_event_record_raw {
> + struct cxl_event_record_hdr hdr;
> + u8 data[CXL_EVENT_RECORD_DATA_LENGTH];
> +} __packed;
> +
> +/*
> + * Get Event Records output payload
> + * CXL rev 3.0 section 8.2.9.2.2; Table 8-50
> + */
> +#define CXL_GET_EVENT_FLAG_OVERFLOW BIT(0)
> +#define CXL_GET_EVENT_FLAG_MORE_RECORDS BIT(1)
> +struct cxl_get_event_payload {
> + u8 flags;
> + u8 reserved1;
> + __le16 overflow_err_count;
> + __le64 first_overflow_timestamp;
> + __le64 last_overflow_timestamp;
> + __le16 record_count;
> + u8 reserved2[10];
> + struct cxl_event_record_raw records[];
> +} __packed;
> +
> +/*
> + * CXL rev 3.0 section 8.2.9.2.2; Table 8-49
> + */
> +enum cxl_event_log_type {
> + CXL_EVENT_TYPE_INFO = 0x00,
> + CXL_EVENT_TYPE_WARN,
> + CXL_EVENT_TYPE_FAIL,
> + CXL_EVENT_TYPE_FATAL,
> + CXL_EVENT_TYPE_MAX
> +};
> +
> +/*
> + * Clear Event Records input payload
> + * CXL rev 3.0 section 8.2.9.2.3; Table 8-51
> + */
> +struct cxl_mbox_clear_event_payload {
> + u8 event_log; /* enum cxl_event_log_type */
> + u8 clear_flags;
> + u8 nr_recs;
> + u8 reserved[3];
> + __le16 handles[];
> +} __packed;
> +#define CXL_CLEAR_EVENT_MAX_HANDLES 0xff /* max based on nr_recs */
> +
> struct cxl_mbox_get_partition_info {
> __le64 active_volatile_cap;
> __le64 active_persistent_cap;
> @@ -441,6 +519,7 @@ int cxl_mem_create_range_info(struct cxl_dev_state *cxlds);
> struct cxl_dev_state *cxl_dev_state_create(struct device *dev);
> void set_exclusive_cxl_commands(struct cxl_dev_state *cxlds, unsigned long *cmds);
> void clear_exclusive_cxl_commands(struct cxl_dev_state *cxlds, unsigned long *cmds);
> +void cxl_mem_get_event_records(struct cxl_dev_state *cxlds, u32 status);
> #ifdef CONFIG_CXL_SUSPEND
> void cxl_mem_active_inc(void);
> void cxl_mem_active_dec(void);
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index 3a66aadb4df0..0fd7742ee70c 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -417,8 +417,39 @@ static void disable_aer(void *pdev)
> pci_disable_pcie_error_reporting(pdev);
> }
>
> +static void cxl_mem_free_event_buffer(void *buf)
> +{
> + kvfree(buf);
> +}
> +
> +/*
> + * There is a single buffer for reading event logs from the mailbox. All logs
> + * share this buffer protected by the cxlds->event_log_lock.
> + */
> +static int cxl_mem_alloc_event_buf(struct cxl_dev_state *cxlds)
> +{
> + struct cxl_get_event_payload *buf;
> + int rc;
> +
> + dev_dbg(cxlds->dev, "Allocating event buffer size %zu\n",
> + cxlds->payload_size);
> +
> + buf = kvmalloc(cxlds->payload_size, GFP_KERNEL);
> + if (!buf)
> + return -ENOMEM;
> +
> + rc = devm_add_action_or_reset(cxlds->dev, cxl_mem_free_event_buffer,
> + buf);
> + if (rc)
> + return rc;
> +
> + cxlds->event.buf = buf;
> + return 0;
> +}
> +
> static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> {
> + struct pci_host_bridge *host_bridge = pci_find_host_bridge(pdev->bus);
> struct cxl_register_map map;
> struct cxl_memdev *cxlmd;
> struct cxl_dev_state *cxlds;
> @@ -494,6 +525,17 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> if (IS_ERR(cxlmd))
> return PTR_ERR(cxlmd);
>
> + /*
> + * When BIOS maintains CXL error reporting control, it will process
> + * event records. Only one agent can do so.
> + */
> + if (host_bridge->native_cxl_error) {
> + rc = cxl_mem_alloc_event_buf(cxlds);
> + if (rc)
> + return rc;
> + cxl_mem_get_event_records(cxlds, CXLDEV_EVENT_STATUS_ALL);
> + }
> +
> if (cxlds->regs.ras) {
> pci_enable_pcie_error_reporting(pdev);
> rc = devm_add_action_or_reset(&pdev->dev, disable_aer, pdev);
>
> --
> 2.39.0
Best Regards,
Huai-Cheng Kuo
