Re: [RFC PATCH v6 01/12] cxl/mbox: Add GET_SUPPORTED_FEATURES mailbox command

[Jonathan Cameron <Jonathan.Cameron@Huawei.com>]

On Thu, 15 Feb 2024 19:14:43 +0800
<shiju.jose@huawei.com> wrote:

> From: Shiju Jose <shiju.jose@huawei.com>
> 
> Add support for GET_SUPPORTED_FEATURES mailbox command.
> 
> CXL spec 3.1 section 8.2.9.6 describes optional device specific features.
> CXL devices supports features with changeable attributes.
> Get Supported Features retrieves the list of supported device specific
> features. The settings of a feature can be retrieved using Get Feature
> and optionally modified using Set Feature.
> 
> Signed-off-by: Shiju Jose <shiju.jose@huawei.com>
Hi Shiju,

Some comment inline.

Mostly just naming suggestions. Actual functionality looks good to me.


> ---
>  drivers/cxl/core/mbox.c | 23 +++++++++++++++
>  drivers/cxl/cxlmem.h    | 62 +++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 85 insertions(+)
> 
> diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
> index 27166a411705..191f51f3df0e 100644
> --- a/drivers/cxl/core/mbox.c
> +++ b/drivers/cxl/core/mbox.c
> @@ -1290,6 +1290,29 @@ int cxl_set_timestamp(struct cxl_memdev_state *mds)
>  }
>  EXPORT_SYMBOL_NS_GPL(cxl_set_timestamp, CXL);
>  
> +int cxl_get_supported_features(struct cxl_memdev_state *mds,
> +						struct cxl_mbox_get_supp_feats_in *pi,
> +						void *feats_out)

Odd indent.  Align the later lines with s of struct

Comments on input types in header below.


> +{
> +	struct cxl_mbox_cmd mbox_cmd;
> +	int rc;
> +
> +	mbox_cmd = (struct cxl_mbox_cmd) {
> +		.opcode = CXL_MBOX_OP_GET_SUPPORTED_FEATURES,
> +		.size_in = sizeof(*pi),
> +		.payload_in = pi,
> +		.size_out = le32_to_cpu(pi->count),
> +		.payload_out = feats_out,
> +		.min_out = sizeof(struct cxl_mbox_get_supp_feats_out),
feats_out should be typed, in which case this becomes
sizeof(*feats_out)

> +	};
> +	rc = cxl_internal_send_cmd(mds, &mbox_cmd);
> +	if (rc < 0)
> +		return rc;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_get_supported_features, 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 5303d6942b88..23e4d98b9bae 100644
> --- a/drivers/cxl/cxlmem.h
> +++ b/drivers/cxl/cxlmem.h
> @@ -529,6 +529,7 @@ enum cxl_opcode {
>  	CXL_MBOX_OP_SET_TIMESTAMP	= 0x0301,
>  	CXL_MBOX_OP_GET_SUPPORTED_LOGS	= 0x0400,
>  	CXL_MBOX_OP_GET_LOG		= 0x0401,
> +	CXL_MBOX_OP_GET_SUPPORTED_FEATURES	= 0x0500,
>  	CXL_MBOX_OP_IDENTIFY		= 0x4000,
>  	CXL_MBOX_OP_GET_PARTITION_INFO	= 0x4100,
>  	CXL_MBOX_OP_SET_PARTITION_INFO	= 0x4101,
> @@ -698,6 +699,64 @@ struct cxl_mbox_set_timestamp_in {
>  
>  } __packed;
>  
> +/* Get Supported Features CXL 3.1 Spec 8.2.9.6.1 */
> +/*
> + * Get Supported Features input payload
> + * CXL rev 3.1 section 8.2.9.6.1 Table 8-95
> + */
> +struct cxl_mbox_get_supp_feats_in {
> +	__le32 count;
> +	__le16 start_index;
> +	u16 reserved;

From a local style point of view using a u16 for reserved is
a new style choice - best to avoid that - most common option looks to
be

	u8 rsvd[2];

> +} __packed;
> +
> +/*
> + * Get Supported Features Supported Feature Entry
> + * CXL rev 3.1 section 8.2.9.6.1 Table 8-97
> + */
> +/* Supported Feature Entry : Payload out attribute flags */
> +#define CXL_FEAT_ENTRY_FLAG_CHANGABLE	BIT(0)
> +#define CXL_FEAT_ENTRY_FLAG_DEEPEST_RESET_PERSISTENCE_MASK	GENMASK(3, 1)
> +#define CXL_FEAT_ENTRY_FLAG_PERSIST_ACROSS_FIRMWARE_UPDATE	BIT(4)
> +#define CXL_FEAT_ENTRY_FLAG_SUPPORT_DEFAULT_SELECTION	BIT(5)
> +#define CXL_FEAT_ENTRY_FLAG_SUPPORT_SAVED_SELECTION	BIT(6)
> +
> +enum cxl_feat_attr_value_persistence {
> +	CXL_FEAT_ATTR_VALUE_PERSISTENCE_NONE,
> +	CXL_FEAT_ATTR_VALUE_PERSISTENCE_CXL_RESET,
> +	CXL_FEAT_ATTR_VALUE_PERSISTENCE_HOT_RESET,
> +	CXL_FEAT_ATTR_VALUE_PERSISTENCE_WARM_RESET,
> +	CXL_FEAT_ATTR_VALUE_PERSISTENCE_COLD_RESET,
> +	CXL_FEAT_ATTR_VALUE_PERSISTENCE_MAX
> +};
> +
> +#define CXL_FEAT_ENTRY_FLAG_PERSISTENCE_ACROSS_FW_UPDATE_MASK	BIT(4)
Not sure there is benefit in defining mask for single bit fields.
Or if there is don't define the value above.
> +#define CXL_FEAT_ENTRY_FLAG_PERSIST_ACROSS_FIRMWARE_UPDATE	BIT(4)

Either is probably fine, just not both!

> +#define CXL_FEAT_ENTRY_FLAG_PERSISTENCE_DEFAULT_SEL_SUPPORT_MASK	BIT(5)
> +#define CXL_FEAT_ENTRY_FLAG_PERSISTENCE_SAVED_SEL_SUPPORT_MASK	BIT(6)
> +
> +struct cxl_mbox_supp_feat_entry {
> +	uuid_t uuid;
> +	__le16 feat_index;

Given it's in a feat entry, could drop 'feat' as redundant info.

	__le16 index;
	__le16 get_size;
etc

> +	__le16 get_feat_size;
> +	__le16 set_feat_size;
> +	__le32 attr_flags;
> +	u8 get_feat_version;
> +	u8 set_feat_version;
> +	__le16 set_feat_effects;
> +	u8 rsvd[18];
> +}  __packed;
> +
> +/*
> + * Get Supported Features output payload
> + * CXL rev 3.1 section 8.2.9.6.1 Table 8-96
> + */
> +struct cxl_mbox_get_supp_feats_out {
> +	__le16 entries;
> +	__le16 nsuppfeats_dev;
Probably don't need the _dev postfix.  Command being sent to a device
so that doesn't add much.

I looked at naming in similar cases.  For mailbox clear we have nr_recs,
so perhaps nr_supported ?

> +	u32 reserved;
	u8 rsvd[4];
as above - match the local syle.
> +	struct cxl_mbox_supp_feat_entry feat_entries[];
> +} __packed;
> +
>  /* Get Poison List  CXL 3.0 Spec 8.2.9.8.4.1 */
>  struct cxl_mbox_poison_in {
>  	__le64 offset;
> @@ -829,6 +888,9 @@ void cxl_event_trace_record(const struct cxl_memdev *cxlmd,
>  			    enum cxl_event_type event_type,
>  			    const uuid_t *uuid, union cxl_event *evt);
>  int cxl_set_timestamp(struct cxl_memdev_state *mds);
> +int cxl_get_supported_features(struct cxl_memdev_state *mds,
> +			       struct cxl_mbox_get_supp_feats_in *pi,
> +			       void *feats_out);


Don't use a void * for that output data.  It should be a
struct cxl_mbox_get_supp_feats_out *

For the input, the other similar functions are providing parameters
directly, not wrapped up in a structure.  Easy enough to do that here
as well as we only need
u32 count, u16 start_index
instead of pi


>  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);