Re: [PATCH V2 03/11] cxl/mem: Implement Clear Event Records command

Jonathan Cameron
2022-12-01T13:26:27Z

On Wed, 30 Nov 2022 16:27:11 -0800
ira.weiny@intel.com wrote:

> From: Ira Weiny <ira.weiny@intel.com>
>
> CXL rev 3.0 section 8.2.9.2.3 defines the Clear Event Records mailbox
> command. After an event record is read it needs to be cleared from the
> event log.
>
> Implement cxl_clear_event_record() to clear all record retrieved from
> the device.
>
> Each record is cleared explicitly. A clear all bit is specified but
> events could arrive between a get and any final clear all operation.
> This means events would be missed.
> Therefore each event is cleared specifically.
>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
I think there is a type issue on the min_t() calculation with that addressed
this looks good to me.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

>
> ---
> Changes from V1:
> Clear Event Record allows for u8 handles while Get Event Record
> allows for u16 records to be returned. Based on Jonathan's
> feedback; allow for all event records to be handled in this
> clear. Which means a double loop with potentially multiple
> Clear Event payloads being sent to clear all events sent.
>
> Changes from RFC:
> Jonathan
> Clean up init of payload and use return code.
> Also report any error to clear the event.
> s/v3.0/rev 3.0
> ---
> drivers/cxl/core/mbox.c | 61 +++++++++++++++++++++++++++++++-----
> drivers/cxl/cxlmem.h | 14 +++++++++
> include/uapi/linux/cxl_mem.h | 1 +
> 3 files changed, 69 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> index 70b681027a3d..076a3df0ba38 100644
> --- a/drivers/cxl/core/mbox.c
> +++ b/drivers/cxl/core/mbox.c
> @@ -52,6 +52,7 @@ static struct cxl_mem_command cxl_mem_commands[CXL_MEM_COMMAND_ID_MAX] = {
> #endif
> CXL_CMD(GET_SUPPORTED_LOGS, 0, CXL_VARIABLE_PAYLOAD, CXL_CMD_FLAG_FORCE_ENABLE),
> CXL_CMD(GET_EVENT_RECORD, 1, CXL_VARIABLE_PAYLOAD, 0),
> + CXL_CMD(CLEAR_EVENT_RECORD, CXL_VARIABLE_PAYLOAD, 0, 0),
> CXL_CMD(GET_FW_INFO, 0, 0x50, 0),
> CXL_CMD(GET_PARTITION_INFO, 0, 0x20, 0),
> CXL_CMD(GET_LSA, 0x8, CXL_VARIABLE_PAYLOAD, 0),
> @@ -708,6 +709,42 @@ 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,
> + u16 total)
> +{
> + struct cxl_mbox_clear_event_payload payload = {
> + .event_log = log,
> + };
> + int cnt;
> +
> + /*
> + * Clear Event Records uses u8 for the handle cnt while Get Event
> + * Record can return up to 0xffff records.
> + */
> + for (cnt = 0; cnt < total; /* cnt incremented internally */) {
> + u8 nr_recs = min_t(u8, (total - cnt),
> + CXL_CLEAR_EVENT_MAX_HANDLES);

I might be half asleep but isn't this assuming that (total - cnt)
fits in an u8? Shouldn't this be min_t(u16, ..)
Also, maybe u16 cnt would be simpler.

Hmm. This is safe but only because of how you call it alongside
handling of a particular Get event records response (which must
have fitted in the mailbox and has a longer header).

Looking at this function in isolation, I think the mailbox could be
small enough that we might not fit 255 records + the header.
Perhaps we need a comment to say that, or at minimum a check and error
return if it won't fit?

> + int i, rc;
> +
> + for (i = 0; i < nr_recs; i++, cnt++) {
> + payload.handle[i] = get_pl->records[cnt].hdr.handle;
> + dev_dbg(cxlds->dev, "Event log '%s': Clearning %u\n",
> + cxl_event_log_type_str(log),
> + le16_to_cpu(payload.handle[i]));
> + }
> + payload.nr_recs = nr_recs;
> +
> + rc = cxl_mbox_send_cmd(cxlds, CXL_MBOX_OP_CLEAR_EVENT_RECORD,
> + &payload, sizeof(payload), NULL, 0);
> + if (rc)
> + return rc;
> + }
> +
> + return 0;
> +}
> +
> static void cxl_mem_get_records_log(struct cxl_dev_state *cxlds,
> enum cxl_event_log_type type)
> {
> @@ -732,13 +769,22 @@ static void cxl_mem_get_records_log(struct cxl_dev_state *cxlds,
This feels miss named now but I can't immediately think of better naming so on that
basis fine to leave it as is if you don't have a better idea!.

> }
>
> nr_rec = le16_to_cpu(payload->record_count);
> - if (trace_cxl_generic_event_enabled()) {
> + if (nr_rec > 0) {
> int i;
>
> - for (i = 0; i < nr_rec; i++)
> - trace_cxl_generic_event(dev_name(cxlds->dev),
> - type,
> - &payload->records[i]);
> + if (trace_cxl_generic_event_enabled()) {
> + for (i = 0; i < nr_rec; i++)
> + trace_cxl_generic_event(dev_name(cxlds->dev),
> + type,
> + &payload->records[i]);
> + }
> +
> + rc = cxl_clear_event_record(cxlds, type, payload, nr_rec);
> + if (rc) {
> + dev_err(cxlds->dev, "Event log '%s': Failed to clear events : %d",
> + cxl_event_log_type_str(type), rc);
> + return;
> + }
> }