RE: [RFC PATCH v9 05/11] cxl/mbox: Add GET_FEATURE mailbox command

[Shiju Jose <shiju.jose@huawei.com>]

>-----Original Message-----
>From: nifan.cxl@gmail.com <nifan.cxl@gmail.com>
>Sent: 17 July 2024 19:08
>To: Shiju Jose <shiju.jose@huawei.com>
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>Subject: Re: [RFC PATCH v9 05/11] cxl/mbox: Add GET_FEATURE mailbox
>command
>
>On Tue, Jul 16, 2024 at 04:03:29PM +0100, shiju.jose@huawei.com wrote:
>> From: Shiju Jose <shiju.jose@huawei.com>
>>
>> Add support for GET_FEATURE mailbox command.
>>
>> CXL spec 3.1 section 8.2.9.6 describes optional device specific features.
>> The settings of a feature can be retrieved using Get Feature command.
>>
>> Signed-off-by: Shiju Jose <shiju.jose@huawei.com>
>> ---
>Minor comments inline.
>
>>  drivers/cxl/core/mbox.c | 37 +++++++++++++++++++++++++++++++++++++
>>  drivers/cxl/cxlmem.h    | 27 +++++++++++++++++++++++++++
>>  2 files changed, 64 insertions(+)
>>
>> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c index
>> 9b9b1d26454e..b1eeed508459 100644
>> --- a/drivers/cxl/core/mbox.c
>> +++ b/drivers/cxl/core/mbox.c
>> @@ -1351,6 +1351,43 @@ int cxl_get_supported_features(struct
>> cxl_memdev_state *mds,  }
>> EXPORT_SYMBOL_NS_GPL(cxl_get_supported_features, CXL);
>>
>> +size_t cxl_get_feature(struct cxl_memdev_state *mds,
>> +		       const uuid_t feat_uuid, void *feat_out,
>> +		       size_t feat_out_size,
>> +		       enum cxl_get_feat_selection selection)
>feat_uuid and selection are both payload inputs, maybe more natural to put
>them together before feat_out.
Will do.
>> +{
>> +	size_t data_to_rd_size, size_out;
>> +	struct cxl_mbox_get_feat_in pi;
>> +	struct cxl_mbox_cmd mbox_cmd;
>> +	size_t data_rcvd_size = 0;
>> +	int rc;
>> +
>> +	size_out = min(feat_out_size, mds->payload_size);
>> +	pi.uuid = feat_uuid;
>> +	pi.selection = selection;
>> +	do {
>> +		data_to_rd_size = min(feat_out_size - data_rcvd_size, mds-
>>payload_size);
>> +		pi.offset = cpu_to_le16(data_rcvd_size);
>> +		pi.count = cpu_to_le16(data_to_rd_size);
>> +
>> +		mbox_cmd = (struct cxl_mbox_cmd) {
>> +			.opcode = CXL_MBOX_OP_GET_FEATURE,
>> +			.size_in = sizeof(pi),
>> +			.payload_in = &pi,
>> +			.size_out = size_out,
>> +			.payload_out = feat_out + data_rcvd_size,
>> +			.min_out = data_to_rd_size,
>> +		};
>> +		rc = cxl_internal_send_cmd(mds, &mbox_cmd);
>> +		if (rc < 0 || mbox_cmd.size_out == 0)
>Is there other case when size_out will be 0 other than the feat_out_size is 0?
I think size_out can be 0 depending on the implementation on the firmware or some
error situation when the feat_out_size is non zero.

>
>If feat_out_size is 0, maybe we return directly, or we use while () {}, instead of
>do {} while.
I had a check for feat_out_size against min feat out size in the previous version. 
Will add return directly if feat_out_size is 0.  
>Anyway, if there is no other case that will return size_out as 0, we can avoid the
>check.
>
>Fan
>> +			return 0;
>> +		data_rcvd_size += mbox_cmd.size_out;
>> +	} while (data_rcvd_size < feat_out_size);
>> +
>> +	return data_rcvd_size;
>> +}
>> +EXPORT_SYMBOL_NS_GPL(cxl_get_feature, CXL);
>> +
>>  int cxl_mem_get_poison(struct cxl_memdev *cxlmd, u64 offset, u64 len,
>>  		       struct cxl_region *cxlr)
>>  {
>> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h index
>> b0e1565b9d2e..25698a6fbe66 100644
>> --- a/drivers/cxl/cxlmem.h
>> +++ b/drivers/cxl/cxlmem.h
>> @@ -531,6 +531,7 @@ enum cxl_opcode {
>>  	CXL_MBOX_OP_CLEAR_LOG           = 0x0403,
>>  	CXL_MBOX_OP_GET_SUP_LOG_SUBLIST = 0x0405,
>>  	CXL_MBOX_OP_GET_SUPPORTED_FEATURES	= 0x0500,
>> +	CXL_MBOX_OP_GET_FEATURE		= 0x0501,
>>  	CXL_MBOX_OP_IDENTIFY		= 0x4000,
>>  	CXL_MBOX_OP_GET_PARTITION_INFO	= 0x4100,
>>  	CXL_MBOX_OP_SET_PARTITION_INFO	= 0x4101,
>> @@ -757,6 +758,28 @@ struct cxl_mbox_get_supp_feats_out {
>>  	struct cxl_mbox_supp_feat_entry feat_entries[];  } __packed;
>>
>> +/*
>> + * Get Feature CXL 3.1 Spec 8.2.9.6.2  */
>> +
>> +/*
>> + * Get Feature input payload
>> + * CXL rev 3.1 section 8.2.9.6.2 Table 8-99  */ enum
>> +cxl_get_feat_selection {
>> +	CXL_GET_FEAT_SEL_CURRENT_VALUE,
>> +	CXL_GET_FEAT_SEL_DEFAULT_VALUE,
>> +	CXL_GET_FEAT_SEL_SAVED_VALUE,
>> +	CXL_GET_FEAT_SEL_MAX
>> +};
>> +
>> +struct cxl_mbox_get_feat_in {
>> +	uuid_t uuid;
>> +	__le16 offset;
>> +	__le16 count;
>> +	u8 selection;
>> +}  __packed;
>> +
>>  /* Get Poison List  CXL 3.0 Spec 8.2.9.8.4.1 */  struct
>> cxl_mbox_poison_in {
>>  	__le64 offset;
>> @@ -891,6 +914,10 @@ int cxl_set_timestamp(struct cxl_memdev_state
>> *mds);  int cxl_get_supported_features(struct cxl_memdev_state *mds,
>>  			       u32 count, u16 start_index,
>>  			       struct cxl_mbox_get_supp_feats_out *feats_out);
>> +size_t cxl_get_feature(struct cxl_memdev_state *mds,
>> +		       const uuid_t feat_uuid, void *feat_out,
>> +		       size_t feat_out_size,
>> +		       enum cxl_get_feat_selection selection);
>>  int cxl_poison_state_init(struct cxl_memdev_state *mds);  int
>> cxl_mem_get_poison(struct cxl_memdev *cxlmd, u64 offset, u64 len,
>>  		       struct cxl_region *cxlr);
>> --
>> 2.34.1
>>

Thanks,
Shiju