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

Jonathan Cameron
2024-02-20T11:03:01Z

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);