[PATCH 2/9] mei: late_bind: add late binding component driver
Greg KH
gregkh at linuxfoundation.org
Wed Jul 16 11:48:38 UTC 2025
On Thu, Jul 10, 2025 at 11:08:33AM -0400, Rodrigo Vivi wrote:
> From: Alexander Usyskin <alexander.usyskin at intel.com>
>
> Introduce a new MEI client driver to support Late Binding firmware
> upload/update for Intel discrete graphics platforms.
>
> Late Binding is a runtime firmware upload/update mechanism that allows
> payloads, such as fan control and voltage regulator, to be securely
> delivered and applied without requiring SPI flash updates or
> system reboots. This driver enables the Xe graphics driver and other
> user-space tools to push such firmware blobs to the authentication
> firmware via the MEI interface.
>
> The driver handles authentication, versioning, and communication
> with the authentication firmware, which in turn coordinates with
> the PUnit/PCODE to apply the payload.
>
> This is a foundational component for enabling dynamic, secure,
> and re-entrant configuration updates on platforms like Battlemage.
>
> Signed-off-by: Alexander Usyskin <alexander.usyskin at intel.com>
> Signed-off-by: Badal Nilawar <badal.nilawar at intel.com>
> Reviewed-by: Anshuman Gupta <anshuman.gupta at intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> ---
>
> Changes in this revision:
> - Proper commit message
> - Proper explanation of 'Late Binding' on Kconfig help and doc
> - Consistency in naming:
> + mei_ prefix where it makes sense
> + use 'lb' for short of 'Late Binding' instead of 'late_bind'
> Including s/CONFIG_INTEL_MEI_LATE_BIND/CONFIG_INTEL_MEI_LB
> + remove stray 'struct module'
> + Fix structs and enum documentation style and fields
> + Remove 'CSC' to avoid yet another acronym. 'Authentication firmware' it is.
> + specify size unit
> + s/push_config/push_payload
>
> drivers/misc/mei/Kconfig | 13 +
> drivers/misc/mei/Makefile | 1 +
> drivers/misc/mei/mei_lb.c | 315 +++++++++++++++++++++
> include/drm/intel/i915_component.h | 1 +
> include/drm/intel/intel_lb_mei_interface.h | 70 +++++
> 5 files changed, 400 insertions(+)
> create mode 100644 drivers/misc/mei/mei_lb.c
> create mode 100644 include/drm/intel/intel_lb_mei_interface.h
>
> diff --git a/drivers/misc/mei/Kconfig b/drivers/misc/mei/Kconfig
> index 7575fee96cc6..f8b04e49e4ba 100644
> --- a/drivers/misc/mei/Kconfig
> +++ b/drivers/misc/mei/Kconfig
> @@ -81,6 +81,19 @@ config INTEL_MEI_VSC
> This driver can also be built as a module. If so, the module
> will be called mei-vsc.
>
> +config INTEL_MEI_LB
> + tristate "Intel Late Binding (LB) support on ME Interface"
> + depends on INTEL_MEI_ME
> + depends on DRM_XE
> + help
> + Enable support for Intel Late Binding (LB) via the MEI interface.
> +
> + Late Binding is a method for applying firmware updates at runtime,
> + allowing the Intel Xe driver to load firmware payloads such as
> + fan controller or voltage regulator. These firmware updates are
> + authenticated and versioned, and do not require firmware flashing
> + or system reboot.
> +
> source "drivers/misc/mei/hdcp/Kconfig"
> source "drivers/misc/mei/pxp/Kconfig"
> source "drivers/misc/mei/gsc_proxy/Kconfig"
> diff --git a/drivers/misc/mei/Makefile b/drivers/misc/mei/Makefile
> index 6f9fdbf1a495..a203ed766b33 100644
> --- a/drivers/misc/mei/Makefile
> +++ b/drivers/misc/mei/Makefile
> @@ -31,6 +31,7 @@ CFLAGS_mei-trace.o = -I$(src)
> obj-$(CONFIG_INTEL_MEI_HDCP) += hdcp/
> obj-$(CONFIG_INTEL_MEI_PXP) += pxp/
> obj-$(CONFIG_INTEL_MEI_GSC_PROXY) += gsc_proxy/
> +obj-$(CONFIG_INTEL_MEI_LB) += mei_lb.o
>
> obj-$(CONFIG_INTEL_MEI_VSC_HW) += mei-vsc-hw.o
> mei-vsc-hw-y := vsc-tp.o
> diff --git a/drivers/misc/mei/mei_lb.c b/drivers/misc/mei/mei_lb.c
> new file mode 100644
> index 000000000000..fddef862712d
> --- /dev/null
> +++ b/drivers/misc/mei/mei_lb.c
> @@ -0,0 +1,315 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2025 Intel Corporation
> + */
> +#include <drm/intel/i915_component.h>
> +#include <drm/intel/intel_lb_mei_interface.h>
> +#include <linux/component.h>
> +#include <linux/pci.h>
> +#include <linux/mei_cl_bus.h>
> +#include <linux/module.h>
> +#include <linux/overflow.h>
> +#include <linux/slab.h>
> +#include <linux/uuid.h>
> +
> +#include "mkhi.h"
> +
> +/**
> + * DOC: Late Binding Firmware Update/Upload
> + *
> + * Late Binding is a firmware update/upload mechanism that allows configuration
> + * payloads to be securely delivered and applied at runtime, rather than
> + * being embedded in the system firmware image (e.g., IFWI or SPI flash).
> + *
> + * This mechanism is used to update device-level configuration such as:
> + * - Fan controller
> + * - Voltage regulator (VR)
> + *
> + * Key Characteristics:
> + * ---------------------
> + * - Runtime Delivery:
> + * Firmware blobs are loaded by the host driver (e.g., Xe KMD)
> + * after the GPU or SoC has booted.
> + *
> + * - Secure and Authenticated:
> + * All payloads are signed and verified by the authentication firmware.
> + *
> + * - No Firmware Flashing Required:
> + * Updates are applied in volatile memory and do not require SPI flash
> + * modification or system reboot.
> + *
> + * - Re-entrant:
> + * Multiple updates of the same or different types can be applied
> + * sequentially within a single boot session.
> + *
> + * - Version Controlled:
> + * Each payload includes version and security version number (SVN)
> + * metadata to support anti-rollback enforcement.
> + *
> + * Upload Flow:
> + * ------------
> + * 1. Host driver (KMD or user-space tool) loads the late binding firmware.
> + * 2. Firmware is passed to the MEI interface and forwarded to
> + * authentication firmware.
> + * 3. Authentication firmware authenticates the payload and extracts
> + * command and data arrays.
> + * 4. Authentication firmware delivers the configuration to PUnit/PCODE.
> + * 5. Status is returned back to the host via MEI.
> + */
> +
> +#define INTEL_LB_CMD 0x12
> +#define INTEL_LB_RSP (INTEL_LB_CMD | 0x80)
> +
> +#define INTEL_LB_SEND_TIMEOUT_MSEC 3000
> +#define INTEL_LB_RECV_TIMEOUT_MSEC 3000
> +
> +/**
> + * struct mei_lb_req - Late Binding request structure
> + * @header: MKHI message header (see struct mkhi_msg_hdr)
> + * @type: Type of the Late Binding payload
> + * @flags: Flags to be passed to the authentication firmware (e.g. %INTEL_LB_FLAGS_IS_PERSISTENT)
> + * @reserved: Reserved for future use by authentication firmware, must be set to 0
> + * @payload_size: Size of the payload data in bytes
> + * @payload: Payload data to be sent to the authentication firmware
> + */
> +struct mei_lb_req {
> + struct mkhi_msg_hdr header;
> + __le32 type;
> + __le32 flags;
> + __le32 reserved[2];
> + __le32 payload_size;
> + u8 payload[] __counted_by(payload_size);
> +} __packed;
> +
> +/**
> + * struct mei_lb_rsp - Late Binding response structure
> + * @header: MKHI message header (see struct mkhi_msg_hdr)
> + * @type: Type of the Late Binding payload
> + * @reserved: Reserved for future use by authentication firmware, must be set to 0
> + * @status: Status returned by authentication firmware (see enum intel_lb_status)
> + */
> +struct mei_lb_rsp {
> + struct mkhi_msg_hdr header;
> + __le32 type;
> + __le32 reserved[2];
> + __le32 status;
> +} __packed;
> +
> +static int mei_lb_check_response(const struct device *dev, const struct mkhi_msg_hdr *hdr)
> +{
> + if (hdr->group_id != MKHI_GROUP_ID_GFX) {
> + dev_err(dev, "Mismatch group id: 0x%x instead of 0x%x\n",
> + hdr->group_id, MKHI_GROUP_ID_GFX);
> + return -EINVAL;
> + }
> +
> + if (hdr->command != INTEL_LB_RSP) {
> + dev_err(dev, "Mismatch command: 0x%x instead of 0x%x\n",
> + hdr->command, INTEL_LB_RSP);
> + return -EINVAL;
> + }
> +
> + if (hdr->result) {
> + dev_err(dev, "Error in result: 0x%x\n", hdr->result);
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +static int mei_lb_push_payload(struct device *dev,
> + enum intel_lb_type type, u32 flags,
> + const void *payload, size_t payload_size)
> +{
> + struct mei_cl_device *cldev;
> + struct mei_lb_req *req = NULL;
> + struct mei_lb_rsp rsp;
> + size_t req_size;
> + ssize_t bytes;
> + int ret;
> +
> + cldev = to_mei_cl_device(dev);
> +
> + ret = mei_cldev_enable(cldev);
> + if (ret) {
> + dev_dbg(dev, "mei_cldev_enable failed. %d\n", ret);
> + return ret;
> + }
> +
> + req_size = struct_size(req, payload, payload_size);
> + if (req_size > mei_cldev_mtu(cldev)) {
> + dev_err(dev, "Payload is too big %zu\n", payload_size);
> + ret = -EMSGSIZE;
> + goto end;
> + }
> +
> + req = kmalloc(req_size, GFP_KERNEL);
> + if (!req) {
> + ret = -ENOMEM;
> + goto end;
> + }
> +
> + req->header.group_id = MKHI_GROUP_ID_GFX;
> + req->header.command = INTEL_LB_CMD;
> + req->type = cpu_to_le32(type);
> + req->flags = cpu_to_le32(flags);
> + req->reserved[0] = 0;
> + req->reserved[1] = 0;
> + req->payload_size = cpu_to_le32(payload_size);
> + memcpy(req->payload, payload, payload_size);
> +
> + bytes = mei_cldev_send_timeout(cldev,
> + (void *)req, req_size, INTEL_LB_SEND_TIMEOUT_MSEC);
> + if (bytes < 0) {
> + dev_err(dev, "mei_cldev_send failed. %zd\n", bytes);
> + ret = bytes;
> + goto end;
> + }
> +
> + bytes = mei_cldev_recv_timeout(cldev,
> + (void *)&rsp, sizeof(rsp), INTEL_LB_RECV_TIMEOUT_MSEC);
> + if (bytes < 0) {
> + dev_err(dev, "mei_cldev_recv failed. %zd\n", bytes);
> + ret = bytes;
> + goto end;
> + }
> + if (bytes < sizeof(rsp.header)) {
> + dev_err(dev, "bad response header from the firmware: size %zd < %zu\n",
> + bytes, sizeof(rsp.header));
> + ret = -EPROTO;
> + goto end;
> + }
> + if (mei_lb_check_response(dev, &rsp.header)) {
> + dev_err(dev, "bad result response from the firmware: 0x%x\n",
> + *(uint32_t *)&rsp.header);
What exactly are you printing out to userspace here? A pointer? Or a
random value from the firmware? Why?
> + ret = -EPROTO;
> + goto end;
> + }
You forgot to check the type and reserved fields of the rsp structure :(
> + if (bytes < sizeof(rsp)) {
> + dev_err(dev, "bad response from the firmware: size %zd < %zu\n",
> + bytes, sizeof(rsp));
> + ret = -EPROTO;
> + goto end;
> + }
Why not check this above when you check against the size of the header?
You only need one size check, not 2.
thanks,
greg k-h
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