Re: [PATCH 3/4] cxl: add a firmware update mechanism using the sysfs firmware loader

[Alison Schofield <alison.schofield@intel.com>]

On Fri, Apr 21, 2023 at 09:09:27PM -0600, Vishal Verma wrote:
> The sysfs based firmware loader mechanism was created to easily allow
> userspace to upload firmware images to FPGA cards. This also happens to
> be pretty suitable to create a user-initiated but kernel-controlled
> firmware update mechanism for CXL devices, using the CXL specified
> mailbox commands.
> 
> Since firmware update commands can be long-running, and can be processed
> in the background by the endpoint device, it is desirable to have the
> ability to chunk the firmware transfer down to smaller pieces, so that
> one operation does not monopolize the mailbox, locking out any other
> long running background commands entirely - e.g. security commands like
> 'sanitize' or poison scanning operations.
> 
> The firmware loader mechanism allows a natural way to perform this
> chunking, as after each mailbox command, that is restricted to the
> maximum mailbox payload size, the cxl memdev driver relinquishes control
> back to the fw_loader system and awaits the next chunk of data to
> transfer. This opens opportunities for other background commands to
> access the mailbox and send their own slices of background commands.
> 
> Add the necessary helpers and state tracking to be able to perform the
> 'Get FW Info', 'Transfer FW', and 'Activate FW' mailbox commands as
> described in the CXL spec. Wire these up to the firmware loader
> callbacks, and register with that system to create the memX/firmware/
> sysfs ABI.

I just have a quick drive-by comment for you....

> 
> Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> ---
>  drivers/cxl/cxlmem.h                    |  79 ++++++++
>  drivers/cxl/core/mbox.c                 |   1 +
>  drivers/cxl/core/memdev.c               | 324 ++++++++++++++++++++++++++++++++
>  Documentation/ABI/testing/sysfs-bus-cxl |  11 ++
>  drivers/cxl/Kconfig                     |   1 +
>  5 files changed, 416 insertions(+)
> 
> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> index 8c3302fc7738..0ecee5b558f4 100644
> --- a/drivers/cxl/cxlmem.h
> +++ b/drivers/cxl/cxlmem.h

snip

> + * Get Firmware Info
> + * CXL rev 3.0 section 8.2.9.3.1; Table 8-56
> + */
> +struct cxl_mbox_get_fw_info {
> +	u8 num_slots;
> +	u8 slot_info;
> +	u8 activation_cap;
> +	u8 reserved[13];
> +	char slot_1_revision[0x10];
> +	char slot_2_revision[0x10];
> +	char slot_3_revision[0x10];
> +	char slot_4_revision[0x10];

The practice here is to use decimals [16]

> +} __packed;
> +

snip

> + * Transfer Firmware Input Payload
> + * CXL rev 3.0 section 8.2.9.3.2; Table 8-57
> + */
> +struct cxl_mbox_transfer_fw {
> +	u8 action;
> +	u8 slot;
> +	u8 reserved[2];
> +	__le32 offset;
> +	u8 reserved2[0x78];

Here too.

That's all for now.