[PATCH v2 0/5] Add support for the TPM FF-A start method

[PATCH v2 0/5] Add support for the TPM FF-A start method

[Stuart Yoder]

Firmware Framework for Arm A-profile (FF-A) is a messaging framework
for Arm-based systems, and in the context of the TPM CRB driver is used
to signal 'start' to a CRB-based TPM service which is hosted in an
FF-A secure partition running in TrustZone.

These patches add support for the CRB FF-A start method defined
in the TCG ACPI specification v1.4 and the FF-A ABI defined
in the Arm TPM Service CRB over FF-A (DEN0138) specification:
https://developer.arm.com/documentation/den0138/latest/

The first patch adds an FF-A driver to handle the FF-A messaging when
communicating with a CRB-based TPM secure partition built on FF-A.
The driver is probed when the TPM secure partition is discovered by
the Linux FF-A infrastructure.

The second patch consolidates the check for idle support in the CRB
driver to one place.

The third patch defines the new ACPI start method enumeration for
CRB over FF-A.

The fourth patch adds support for the FF-A ACPI start method to
the TPM crb driver.

The fifth patch adds documentation explaining how the CRB driver
and FF-A relate.

Version 2
-updates to cover letter to define FF-A
-added new patch with documentation
-created pull request in ACPIA and added link to the patch
 updating actbl3.h
-added tpm_ prefix to the FF-A CRB driver

Stuart Yoder (5):
  tpm_crb: implement driver compliant to CRB over FF-A
  tpm_crb: refactor check for idle support into TPM into inline function
  ACPICA: add start method for Arm FF-A
  tpm_crb: add support for the Arm FF-A start method
  Documentation: tpm: add documentation for the CRB FF-A interface

 Documentation/security/tpm/tpm_ffa_crb.rst |  65 +++++
 drivers/char/tpm/Kconfig                   |   9 +
 drivers/char/tpm/Makefile                  |   1 +
 drivers/char/tpm/tpm_crb.c                 |  81 +++++-
 drivers/char/tpm/tpm_ffa_crb.c             | 310 +++++++++++++++++++++
 drivers/char/tpm/tpm_ffa_crb.h             |  30 ++
 include/acpi/actbl3.h                      |   1 +
 7 files changed, 491 insertions(+), 6 deletions(-)
 create mode 100644 Documentation/security/tpm/tpm_ffa_crb.rst
 create mode 100644 drivers/char/tpm/tpm_ffa_crb.c
 create mode 100644 drivers/char/tpm/tpm_ffa_crb.h

-- 
2.34.1

[PATCH v2 1/5] tpm_crb: implement driver compliant to CRB over FF-A

[Stuart Yoder]

The Arm specification TPM Service CRB over FF-A specification
defines the FF-A messages to interact with a CRB-based TPM
implemented as an FF-A secure partition.

Spec URL:
https://developer.arm.com/documentation/den0138/latest/

This driver is probed when a TPM Secure Partition is
discovered by the FF-A subsystem. It exposes APIs
used by the TPM CRB driver to send notifications to
the TPM.

Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
---
 drivers/char/tpm/Kconfig       |   9 +
 drivers/char/tpm/Makefile      |   1 +
 drivers/char/tpm/tpm_ffa_crb.c | 310 +++++++++++++++++++++++++++++++++
 drivers/char/tpm/tpm_ffa_crb.h |  30 ++++
 4 files changed, 350 insertions(+)
 create mode 100644 drivers/char/tpm/tpm_ffa_crb.c
 create mode 100644 drivers/char/tpm/tpm_ffa_crb.h

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index 0fc9a510e059..af5ba7c63927 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -210,6 +210,15 @@ config TCG_CRB
 	  from within Linux.  To compile this driver as a module, choose
 	  M here; the module will be called tpm_crb.
 
+config TCG_ARM_FFA_CRB
+	tristate "TPM CRB over Arm FF-A Transport"
+	depends on ARM_FFA_TRANSPORT
+	default y if (TCG_CRB && ARM_FFA_TRANSPORT)
+	help
+	  If the Arm FF-A transport is used to access the TPM say Yes.
+	  To compile this driver as a module, choose M here; the module
+	  will be called tpm_ffa_crb.
+
 config TCG_VTPM_PROXY
 	tristate "VTPM Proxy Interface"
 	depends on TCG_TPM
diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index 9bb142c75243..21f2eb5a485e 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -42,5 +42,6 @@ obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o
 obj-$(CONFIG_TCG_TIS_ST33ZP24) += st33zp24/
 obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
 obj-$(CONFIG_TCG_CRB) += tpm_crb.o
+obj-$(CONFIG_TCG_ARM_FFA_CRB) += tpm_ffa_crb.o
 obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
 obj-$(CONFIG_TCG_FTPM_TEE) += tpm_ftpm_tee.o
diff --git a/drivers/char/tpm/tpm_ffa_crb.c b/drivers/char/tpm/tpm_ffa_crb.c
new file mode 100644
index 000000000000..56bd77864a47
--- /dev/null
+++ b/drivers/char/tpm/tpm_ffa_crb.c
@@ -0,0 +1,310 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024 Arm Ltd.
+ *
+ * Maintained by: <tpmdd-devel@lists.sourceforge.net>
+ *
+ * This device driver implements the TPM CRB start method
+ * as defined in the TPM Service Command Response Buffer
+ * Interface Over FF-A (DEN0138).
+ */
+
+#define pr_fmt(fmt) "FFA_CRB: " fmt
+
+#include <linux/arm_ffa.h>
+#include "tpm_ffa_crb.h"
+
+/* TPM service function status codes */
+#define FFA_CRB_OK			0x05000001
+#define FFA_CRB_OK_RESULTS_RETURNED	0x05000002
+#define FFA_CRB_NOFUNC			0x8e000001
+#define FFA_CRB_NOTSUP			0x8e000002
+#define FFA_CRB_INVARG			0x8e000005
+#define FFA_CRB_INV_CRB_CTRL_DATA	0x8e000006
+#define FFA_CRB_ALREADY			0x8e000009
+#define FFA_CRB_DENIED			0x8e00000a
+#define FFA_CRB_NOMEM			0x8e00000b
+
+#define FFA_CRB_VERSION_MAJOR	1
+#define FFA_CRB_VERSION_MINOR	0
+
+/* version encoding */
+#define FFA_CRB_MAJOR_VERSION_MASK  GENMASK(30, 16)
+#define FFA_CRB_MINOR_VERSION_MASK  GENMASK(15, 0)
+#define FFA_CRB_MAJOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_MAJOR_VERSION_MASK, (x))))
+#define FFA_CRB_MINOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_MINOR_VERSION_MASK, (x))))
+
+/*
+ * Normal world sends requests with FFA_MSG_SEND_DIRECT_REQ and
+ * responses are returned with FFA_MSG_SEND_DIRECT_RESP for normal
+ * messages.
+ *
+ * All requests with FFA_MSG_SEND_DIRECT_REQ and FFA_MSG_SEND_DIRECT_RESP
+ * are using the AArch32 SMC calling convention with register usage as
+ * defined in FF-A specification:
+ * w0:    Function ID (0x8400006F or 0x84000070)
+ * w1:    Source/Destination IDs
+ * w2:    Reserved (MBZ)
+ * w3-w7: Implementation defined, free to be used below
+ */
+
+/*
+ * Returns the version of the interface that is available
+ * Call register usage:
+ * w3:    Not used (MBZ)
+ * w4:    TPM service function ID, FFA_CRB_GET_INTERFACE_VERSION
+ * w5-w7: Reserved (MBZ)
+ *
+ * Return register usage:
+ * w3:    Not used (MBZ)
+ * w4:    TPM service function status
+ * w5:    TPM service interface version
+ *        Bits[31:16]: major version
+ *        Bits[15:0]: minor version
+ * w6-w7: Reserved (MBZ)
+ *
+ * Possible function status codes in register w4:
+ *     CRB_FFA_OK_RESULTS_RETURNED: The version of the interface has been
+ *                                  returned.
+ */
+#define FFA_CRB_GET_INTERFACE_VERSION 0x0f000001
+
+/*
+ * Return information on a given feature of the TPM service
+ * Call register usage:
+ * w3:    Not used (MBZ)
+ * w4:    TPM service function ID, FFA_CRB_START
+ * w5:    Start function qualifier
+ *            Bits[31:8] (MBZ)
+ *            Bits[7:0]
+ *              0: Notifies TPM that a command is ready to be processed
+ *              1: Notifies TPM that a locality request is ready to be processed
+ * w6:    TPM locality, one of 0..4
+ *            -If the start function qualifier is 0, identifies the locality
+ *             from where the command originated.
+ *            -If the start function qualifier is 1, identifies the locality
+ *             of the locality request
+ * w6-w7: Reserved (MBZ)
+ *
+ * Return register usage:
+ * w3:    Not used (MBZ)
+ * w4:    TPM service function status
+ * w5-w7: Reserved (MBZ)
+ *
+ * Possible function status codes in register w4:
+ *     FFA_CRB_OK: the TPM service has been notified successfully
+ *     FFA_CRB_INVARG: one or more arguments are not valid
+ *     FFA_CRB_INV_CRB_CTRL_DATA: CRB control data or locality control
+ *         data at the given TPM locality is not valid
+ *     FFA_CRB_DENIED: the TPM has previously disabled locality requests and
+ *         command processing at the given locality
+ */
+#define FFA_CRB_START 0x0f000201
+
+struct ffa_crb {
+	struct ffa_device *ffa_dev;
+	u16 major_version;
+	u16 minor_version;
+	struct mutex msg_data_lock;
+	struct ffa_send_direct_data direct_msg_data;
+};
+
+static struct ffa_crb *ffa_crb;
+
+static int ffa_crb_to_linux_errno(int errno)
+{
+	int rc;
+
+	switch (errno) {
+	case FFA_CRB_OK:
+		rc = 0;
+		break;
+	case FFA_CRB_OK_RESULTS_RETURNED:
+		rc = 0;
+		break;
+	case FFA_CRB_NOFUNC:
+		rc = -ENOENT;
+		break;
+	case FFA_CRB_NOTSUP:
+		rc = -EPERM;
+		break;
+	case FFA_CRB_INVARG:
+		rc = -EINVAL;
+		break;
+	case FFA_CRB_INV_CRB_CTRL_DATA:
+		rc = -ENOEXEC;
+		break;
+	case FFA_CRB_ALREADY:
+		rc = -EEXIST;
+		break;
+	case FFA_CRB_DENIED:
+		rc = -EACCES;
+		break;
+	case FFA_CRB_NOMEM:
+		rc = -ENOMEM;
+		break;
+	default:
+		rc = -EINVAL;
+	}
+
+	return rc;
+}
+
+int ffa_crb_init(void)
+{
+	if (ffa_crb == NULL)
+		return -ENOENT;
+
+	if (IS_ERR_VALUE(ffa_crb))
+		return -ENODEV;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(ffa_crb_init);
+
+static int __ffa_crb_send_recieve(unsigned long func_id,
+		unsigned long a0, unsigned long a1, unsigned long a2)
+{
+	int ret;
+	const struct ffa_msg_ops *msg_ops;
+
+	if (ffa_crb == NULL)
+		return -ENOENT;
+
+	msg_ops = ffa_crb->ffa_dev->ops->msg_ops;
+
+	memset(&ffa_crb->direct_msg_data, 0x00,
+			sizeof(struct ffa_send_direct_data));
+
+	ffa_crb->direct_msg_data.data1 = func_id;
+	ffa_crb->direct_msg_data.data2 = a0;
+	ffa_crb->direct_msg_data.data3 = a1;
+	ffa_crb->direct_msg_data.data4 = a2;
+
+	ret = msg_ops->sync_send_receive(ffa_crb->ffa_dev,
+			&ffa_crb->direct_msg_data);
+	if (!ret)
+		ret = ffa_crb_to_linux_errno(ffa_crb->direct_msg_data.data1);
+
+	return ret;
+}
+
+int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor)
+{
+	int rc;
+
+	if (ffa_crb == NULL)
+		return -ENOENT;
+
+	if (IS_ERR_VALUE(ffa_crb))
+		return -ENODEV;
+
+	if (major == NULL || minor == NULL)
+		return -EINVAL;
+
+	guard(mutex)(&ffa_crb->msg_data_lock);
+
+	rc = __ffa_crb_send_recieve(FFA_CRB_GET_INTERFACE_VERSION, 0x00, 0x00, 0x00);
+	if (!rc) {
+		*major = FFA_CRB_MAJOR_VERSION(ffa_crb->direct_msg_data.data2);
+		*minor = FFA_CRB_MINOR_VERSION(ffa_crb->direct_msg_data.data2);
+	}
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(ffa_crb_get_interface_version);
+
+int ffa_crb_start(int request_type, int locality)
+{
+	if (ffa_crb == NULL)
+		return -ENOENT;
+
+	if (IS_ERR_VALUE(ffa_crb))
+		return -ENODEV;
+
+	guard(mutex)(&ffa_crb->msg_data_lock);
+
+	return __ffa_crb_send_recieve(FFA_CRB_START, request_type, locality, 0x00);
+}
+EXPORT_SYMBOL_GPL(ffa_crb_start);
+
+static int ffa_crb_probe(struct ffa_device *ffa_dev)
+{
+	int rc;
+	struct ffa_crb *p;
+
+	/* only one instance of a TPM partition is supported */
+	if (ffa_crb && !IS_ERR_VALUE(ffa_crb))
+		return -EEXIST;
+
+	ffa_crb = ERR_PTR(-ENODEV); // set ffa_crb so we can detect probe failure
+
+	if (!ffa_partition_supports_direct_recv(ffa_dev)) {
+		pr_err("TPM partition doesn't support direct message receive.\n");
+		return -EINVAL;
+	}
+
+	p = kzalloc(sizeof(*ffa_crb), GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+	ffa_crb = p;
+
+	mutex_init(&ffa_crb->msg_data_lock);
+	ffa_crb->ffa_dev = ffa_dev;
+	ffa_dev_set_drvdata(ffa_dev, ffa_crb);
+
+	/* if TPM is aarch32 use 32-bit SMCs */
+	if (!ffa_partition_check_property(ffa_dev, FFA_PARTITION_AARCH64_EXEC))
+		ffa_dev->ops->msg_ops->mode_32bit_set(ffa_dev);
+
+	/* verify compatibility of TPM service version number */
+	rc = ffa_crb_get_interface_version(&ffa_crb->major_version,
+			&ffa_crb->minor_version);
+	if (rc) {
+		pr_err("failed to get crb interface version. rc:%d", rc);
+		goto out;
+	}
+
+	pr_info("ABI version %u.%u", ffa_crb->major_version,
+		ffa_crb->minor_version);
+
+	if ((ffa_crb->major_version != FFA_CRB_VERSION_MAJOR) ||
+	    (ffa_crb->minor_version < FFA_CRB_VERSION_MINOR)) {
+		pr_err("Incompatible ABI version");
+		goto out;
+	}
+
+	return 0;
+
+out:
+	kfree(ffa_crb);
+	ffa_crb = ERR_PTR(-ENODEV);
+	return -EINVAL;
+}
+
+static void ffa_crb_remove(struct ffa_device *ffa_dev)
+{
+	kfree(ffa_crb);
+	ffa_crb = NULL;
+}
+
+static const struct ffa_device_id ffa_crb_device_id[] = {
+	/* 17b862a4-1806-4faf-86b3-089a58353861 */
+	{ UUID_INIT(0x17b862a4, 0x1806, 0x4faf,
+		    0x86, 0xb3, 0x08, 0x9a, 0x58, 0x35, 0x38, 0x61) },
+	{}
+};
+
+static struct ffa_driver ffa_crb_driver = {
+	.name = "ffa-crb",
+	.probe = ffa_crb_probe,
+	.remove = ffa_crb_remove,
+	.id_table = ffa_crb_device_id,
+};
+
+module_ffa_driver(ffa_crb_driver);
+
+MODULE_AUTHOR("Arm");
+MODULE_DESCRIPTION("FFA CRB driver");
+MODULE_VERSION("1.0");
+MODULE_LICENSE("GPL");
diff --git a/drivers/char/tpm/tpm_ffa_crb.h b/drivers/char/tpm/tpm_ffa_crb.h
new file mode 100644
index 000000000000..42327d285165
--- /dev/null
+++ b/drivers/char/tpm/tpm_ffa_crb.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2024 Arm Ltd.
+ *
+ * Authors:
+ * Stuart Yoder <stuart.yoder@arm.com>
+ *
+ * Maintained by: <tpmdd-devel@lists.sourceforge.net>
+ *
+ * This device driver implements the TPM CRB start method
+ * as defined in the TPM Service Command Response Buffer
+ * Interface Over FF-A (DEN0138).
+ */
+#ifndef _FFA_CRB_H
+#define _FFA_CRB_H
+
+#if IS_ENABLED(CONFIG_TCG_ARM_FFA_CRB)
+int ffa_crb_init(void);
+int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor);
+int ffa_crb_start(int request_type, int locality);
+#else
+static inline int ffa_crb_init(void) { return 0; }
+static inline int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor) { return 0; }
+static inline int ffa_crb_start(int request_type, int locality) { return 0; }
+#endif
+
+#define FFA_CRB_START_TYPE_COMMAND 0
+#define FFA_CRB_START_TYPE_LOCALITY_REQUEST 1
+
+#endif
-- 
2.34.1

Re: [PATCH v2 1/5] tpm_crb: implement driver compliant to CRB over FF-A

[Jarkko Sakkinen]

On Wed, Feb 12, 2025 at 04:05:44PM -0600, Stuart Yoder wrote:
> The Arm specification TPM Service CRB over FF-A specification
> defines the FF-A messages to interact with a CRB-based TPM
> implemented as an FF-A secure partition.
> 
> Spec URL:
> https://developer.arm.com/documentation/den0138/latest/
> 
> This driver is probed when a TPM Secure Partition is
> discovered by the FF-A subsystem. It exposes APIs
> used by the TPM CRB driver to send notifications to
> the TPM.
> 
> Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
> ---
>  drivers/char/tpm/Kconfig       |   9 +
>  drivers/char/tpm/Makefile      |   1 +
>  drivers/char/tpm/tpm_ffa_crb.c | 310 +++++++++++++++++++++++++++++++++
>  drivers/char/tpm/tpm_ffa_crb.h |  30 ++++
>  4 files changed, 350 insertions(+)
>  create mode 100644 drivers/char/tpm/tpm_ffa_crb.c
>  create mode 100644 drivers/char/tpm/tpm_ffa_crb.h
> 
> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> index 0fc9a510e059..af5ba7c63927 100644
> --- a/drivers/char/tpm/Kconfig
> +++ b/drivers/char/tpm/Kconfig
> @@ -210,6 +210,15 @@ config TCG_CRB
>  	  from within Linux.  To compile this driver as a module, choose
>  	  M here; the module will be called tpm_crb.
>  
> +config TCG_ARM_FFA_CRB
> +	tristate "TPM CRB over Arm FF-A Transport"
> +	depends on ARM_FFA_TRANSPORT
> +	default y if (TCG_CRB && ARM_FFA_TRANSPORT)
> +	help
> +	  If the Arm FF-A transport is used to access the TPM say Yes.
> +	  To compile this driver as a module, choose M here; the module
> +	  will be called tpm_ffa_crb.
> +
>  config TCG_VTPM_PROXY
>  	tristate "VTPM Proxy Interface"
>  	depends on TCG_TPM
> diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
> index 9bb142c75243..21f2eb5a485e 100644
> --- a/drivers/char/tpm/Makefile
> +++ b/drivers/char/tpm/Makefile
> @@ -42,5 +42,6 @@ obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o
>  obj-$(CONFIG_TCG_TIS_ST33ZP24) += st33zp24/
>  obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
>  obj-$(CONFIG_TCG_CRB) += tpm_crb.o
> +obj-$(CONFIG_TCG_ARM_FFA_CRB) += tpm_ffa_crb.o
>  obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
>  obj-$(CONFIG_TCG_FTPM_TEE) += tpm_ftpm_tee.o
> diff --git a/drivers/char/tpm/tpm_ffa_crb.c b/drivers/char/tpm/tpm_ffa_crb.c
> new file mode 100644
> index 000000000000..56bd77864a47
> --- /dev/null
> +++ b/drivers/char/tpm/tpm_ffa_crb.c
> @@ -0,0 +1,310 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2024 Arm Ltd.
> + *
> + * Maintained by: <tpmdd-devel@lists.sourceforge.net>
> + *
> + * This device driver implements the TPM CRB start method
> + * as defined in the TPM Service Command Response Buffer
> + * Interface Over FF-A (DEN0138).
> + */
> +
> +#define pr_fmt(fmt) "FFA_CRB: " fmt
> +
> +#include <linux/arm_ffa.h>
> +#include "tpm_ffa_crb.h"
> +
> +/* TPM service function status codes */
> +#define FFA_CRB_OK			0x05000001
> +#define FFA_CRB_OK_RESULTS_RETURNED	0x05000002
> +#define FFA_CRB_NOFUNC			0x8e000001
> +#define FFA_CRB_NOTSUP			0x8e000002
> +#define FFA_CRB_INVARG			0x8e000005
> +#define FFA_CRB_INV_CRB_CTRL_DATA	0x8e000006
> +#define FFA_CRB_ALREADY			0x8e000009
> +#define FFA_CRB_DENIED			0x8e00000a
> +#define FFA_CRB_NOMEM			0x8e00000b
> +
> +#define FFA_CRB_VERSION_MAJOR	1
> +#define FFA_CRB_VERSION_MINOR	0
> +
> +/* version encoding */
> +#define FFA_CRB_MAJOR_VERSION_MASK  GENMASK(30, 16)
> +#define FFA_CRB_MINOR_VERSION_MASK  GENMASK(15, 0)
> +#define FFA_CRB_MAJOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_MAJOR_VERSION_MASK, (x))))
> +#define FFA_CRB_MINOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_MINOR_VERSION_MASK, (x))))
> +
> +/*
> + * Normal world sends requests with FFA_MSG_SEND_DIRECT_REQ and
> + * responses are returned with FFA_MSG_SEND_DIRECT_RESP for normal
> + * messages.
> + *
> + * All requests with FFA_MSG_SEND_DIRECT_REQ and FFA_MSG_SEND_DIRECT_RESP
> + * are using the AArch32 SMC calling convention with register usage as
> + * defined in FF-A specification:
> + * w0:    Function ID (0x8400006F or 0x84000070)
> + * w1:    Source/Destination IDs
> + * w2:    Reserved (MBZ)
> + * w3-w7: Implementation defined, free to be used below
> + */
> +
> +/*
> + * Returns the version of the interface that is available
> + * Call register usage:
> + * w3:    Not used (MBZ)
> + * w4:    TPM service function ID, FFA_CRB_GET_INTERFACE_VERSION
> + * w5-w7: Reserved (MBZ)
> + *
> + * Return register usage:
> + * w3:    Not used (MBZ)
> + * w4:    TPM service function status
> + * w5:    TPM service interface version
> + *        Bits[31:16]: major version
> + *        Bits[15:0]: minor version
> + * w6-w7: Reserved (MBZ)
> + *
> + * Possible function status codes in register w4:
> + *     CRB_FFA_OK_RESULTS_RETURNED: The version of the interface has been
> + *                                  returned.
> + */
> +#define FFA_CRB_GET_INTERFACE_VERSION 0x0f000001
> +
> +/*
> + * Return information on a given feature of the TPM service
> + * Call register usage:
> + * w3:    Not used (MBZ)
> + * w4:    TPM service function ID, FFA_CRB_START
> + * w5:    Start function qualifier
> + *            Bits[31:8] (MBZ)
> + *            Bits[7:0]
> + *              0: Notifies TPM that a command is ready to be processed
> + *              1: Notifies TPM that a locality request is ready to be processed
> + * w6:    TPM locality, one of 0..4
> + *            -If the start function qualifier is 0, identifies the locality
> + *             from where the command originated.
> + *            -If the start function qualifier is 1, identifies the locality
> + *             of the locality request
> + * w6-w7: Reserved (MBZ)
> + *
> + * Return register usage:
> + * w3:    Not used (MBZ)
> + * w4:    TPM service function status
> + * w5-w7: Reserved (MBZ)
> + *
> + * Possible function status codes in register w4:
> + *     FFA_CRB_OK: the TPM service has been notified successfully
> + *     FFA_CRB_INVARG: one or more arguments are not valid
> + *     FFA_CRB_INV_CRB_CTRL_DATA: CRB control data or locality control
> + *         data at the given TPM locality is not valid
> + *     FFA_CRB_DENIED: the TPM has previously disabled locality requests and
> + *         command processing at the given locality
> + */
> +#define FFA_CRB_START 0x0f000201
> +
> +struct ffa_crb {
> +	struct ffa_device *ffa_dev;
> +	u16 major_version;
> +	u16 minor_version;
> +	struct mutex msg_data_lock;
> +	struct ffa_send_direct_data direct_msg_data;
> +};
> +
> +static struct ffa_crb *ffa_crb;
> +
> +static int ffa_crb_to_linux_errno(int errno)
> +{
> +	int rc;
> +
> +	switch (errno) {
> +	case FFA_CRB_OK:
> +		rc = 0;
> +		break;
> +	case FFA_CRB_OK_RESULTS_RETURNED:
> +		rc = 0;
> +		break;
> +	case FFA_CRB_NOFUNC:
> +		rc = -ENOENT;
> +		break;
> +	case FFA_CRB_NOTSUP:
> +		rc = -EPERM;
> +		break;
> +	case FFA_CRB_INVARG:
> +		rc = -EINVAL;
> +		break;
> +	case FFA_CRB_INV_CRB_CTRL_DATA:
> +		rc = -ENOEXEC;
> +		break;
> +	case FFA_CRB_ALREADY:
> +		rc = -EEXIST;
> +		break;
> +	case FFA_CRB_DENIED:
> +		rc = -EACCES;
> +		break;
> +	case FFA_CRB_NOMEM:
> +		rc = -ENOMEM;
> +		break;
> +	default:
> +		rc = -EINVAL;
> +	}
> +
> +	return rc;
> +}
> +
> +int ffa_crb_init(void)
> +{
> +	if (ffa_crb == NULL)
> +		return -ENOENT;
> +
> +	if (IS_ERR_VALUE(ffa_crb))
> +		return -ENODEV;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(ffa_crb_init);
> +
> +static int __ffa_crb_send_recieve(unsigned long func_id,
> +		unsigned long a0, unsigned long a1, unsigned long a2)
> +{
> +	int ret;
> +	const struct ffa_msg_ops *msg_ops;
> +
> +	if (ffa_crb == NULL)
> +		return -ENOENT;
> +
> +	msg_ops = ffa_crb->ffa_dev->ops->msg_ops;
> +
> +	memset(&ffa_crb->direct_msg_data, 0x00,
> +			sizeof(struct ffa_send_direct_data));
> +
> +	ffa_crb->direct_msg_data.data1 = func_id;
> +	ffa_crb->direct_msg_data.data2 = a0;
> +	ffa_crb->direct_msg_data.data3 = a1;
> +	ffa_crb->direct_msg_data.data4 = a2;
> +
> +	ret = msg_ops->sync_send_receive(ffa_crb->ffa_dev,
> +			&ffa_crb->direct_msg_data);
> +	if (!ret)
> +		ret = ffa_crb_to_linux_errno(ffa_crb->direct_msg_data.data1);
> +
> +	return ret;
> +}
> +
> +int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor)
> +{
> +	int rc;
> +
> +	if (ffa_crb == NULL)
> +		return -ENOENT;
> +
> +	if (IS_ERR_VALUE(ffa_crb))
> +		return -ENODEV;
> +
> +	if (major == NULL || minor == NULL)
> +		return -EINVAL;
> +
> +	guard(mutex)(&ffa_crb->msg_data_lock);
> +
> +	rc = __ffa_crb_send_recieve(FFA_CRB_GET_INTERFACE_VERSION, 0x00, 0x00, 0x00);
> +	if (!rc) {
> +		*major = FFA_CRB_MAJOR_VERSION(ffa_crb->direct_msg_data.data2);
> +		*minor = FFA_CRB_MINOR_VERSION(ffa_crb->direct_msg_data.data2);
> +	}
> +
> +	return rc;
> +}
> +EXPORT_SYMBOL_GPL(ffa_crb_get_interface_version);
> +
> +int ffa_crb_start(int request_type, int locality)
> +{
> +	if (ffa_crb == NULL)
> +		return -ENOENT;
> +
> +	if (IS_ERR_VALUE(ffa_crb))
> +		return -ENODEV;
> +
> +	guard(mutex)(&ffa_crb->msg_data_lock);
> +
> +	return __ffa_crb_send_recieve(FFA_CRB_START, request_type, locality, 0x00);
> +}
> +EXPORT_SYMBOL_GPL(ffa_crb_start);
> +
> +static int ffa_crb_probe(struct ffa_device *ffa_dev)
> +{
> +	int rc;
> +	struct ffa_crb *p;
> +
> +	/* only one instance of a TPM partition is supported */
> +	if (ffa_crb && !IS_ERR_VALUE(ffa_crb))
> +		return -EEXIST;
> +
> +	ffa_crb = ERR_PTR(-ENODEV); // set ffa_crb so we can detect probe failure
> +
> +	if (!ffa_partition_supports_direct_recv(ffa_dev)) {
> +		pr_err("TPM partition doesn't support direct message receive.\n");
> +		return -EINVAL;
> +	}
> +
> +	p = kzalloc(sizeof(*ffa_crb), GFP_KERNEL);
> +	if (!p)
> +		return -ENOMEM;
> +	ffa_crb = p;
> +
> +	mutex_init(&ffa_crb->msg_data_lock);
> +	ffa_crb->ffa_dev = ffa_dev;
> +	ffa_dev_set_drvdata(ffa_dev, ffa_crb);
> +
> +	/* if TPM is aarch32 use 32-bit SMCs */
> +	if (!ffa_partition_check_property(ffa_dev, FFA_PARTITION_AARCH64_EXEC))
> +		ffa_dev->ops->msg_ops->mode_32bit_set(ffa_dev);
> +
> +	/* verify compatibility of TPM service version number */
> +	rc = ffa_crb_get_interface_version(&ffa_crb->major_version,
> +			&ffa_crb->minor_version);
> +	if (rc) {
> +		pr_err("failed to get crb interface version. rc:%d", rc);
> +		goto out;
> +	}
> +
> +	pr_info("ABI version %u.%u", ffa_crb->major_version,
> +		ffa_crb->minor_version);
> +
> +	if ((ffa_crb->major_version != FFA_CRB_VERSION_MAJOR) ||
> +	    (ffa_crb->minor_version < FFA_CRB_VERSION_MINOR)) {
> +		pr_err("Incompatible ABI version");
> +		goto out;
> +	}
> +
> +	return 0;
> +
> +out:
> +	kfree(ffa_crb);
> +	ffa_crb = ERR_PTR(-ENODEV);
> +	return -EINVAL;
> +}
> +
> +static void ffa_crb_remove(struct ffa_device *ffa_dev)
> +{
> +	kfree(ffa_crb);
> +	ffa_crb = NULL;
> +}
> +
> +static const struct ffa_device_id ffa_crb_device_id[] = {
> +	/* 17b862a4-1806-4faf-86b3-089a58353861 */
> +	{ UUID_INIT(0x17b862a4, 0x1806, 0x4faf,
> +		    0x86, 0xb3, 0x08, 0x9a, 0x58, 0x35, 0x38, 0x61) },
> +	{}
> +};
> +
> +static struct ffa_driver ffa_crb_driver = {
> +	.name = "ffa-crb",
> +	.probe = ffa_crb_probe,
> +	.remove = ffa_crb_remove,
> +	.id_table = ffa_crb_device_id,
> +};
> +
> +module_ffa_driver(ffa_crb_driver);
> +
> +MODULE_AUTHOR("Arm");
> +MODULE_DESCRIPTION("FFA CRB driver");
> +MODULE_VERSION("1.0");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/char/tpm/tpm_ffa_crb.h b/drivers/char/tpm/tpm_ffa_crb.h
> new file mode 100644
> index 000000000000..42327d285165
> --- /dev/null
> +++ b/drivers/char/tpm/tpm_ffa_crb.h
> @@ -0,0 +1,30 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2024 Arm Ltd.
> + *
> + * Authors:
> + * Stuart Yoder <stuart.yoder@arm.com>
> + *
> + * Maintained by: <tpmdd-devel@lists.sourceforge.net>
> + *
> + * This device driver implements the TPM CRB start method
> + * as defined in the TPM Service Command Response Buffer
> + * Interface Over FF-A (DEN0138).
> + */
> +#ifndef _FFA_CRB_H
> +#define _FFA_CRB_H
> +
> +#if IS_ENABLED(CONFIG_TCG_ARM_FFA_CRB)
> +int ffa_crb_init(void);
> +int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor);
> +int ffa_crb_start(int request_type, int locality);
> +#else
> +static inline int ffa_crb_init(void) { return 0; }
> +static inline int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor) { return 0; }
> +static inline int ffa_crb_start(int request_type, int locality) { return 0; }
> +#endif
> +
> +#define FFA_CRB_START_TYPE_COMMAND 0
> +#define FFA_CRB_START_TYPE_LOCALITY_REQUEST 1
> +
> +#endif
> -- 
> 2.34.1
> 
> 

tpm_crb_ffa_*

BR, Jarkko

Re: [PATCH v2 1/5] tpm_crb: implement driver compliant to CRB over FF-A

[Stuart Yoder]

On 2/13/25 4:14 PM, Jarkko Sakkinen wrote:
> On Wed, Feb 12, 2025 at 04:05:44PM -0600, Stuart Yoder wrote:
>> The Arm specification TPM Service CRB over FF-A specification
>> defines the FF-A messages to interact with a CRB-based TPM
>> implemented as an FF-A secure partition.
>>
>> Spec URL:
>> https://developer.arm.com/documentation/den0138/latest/
>>
>> This driver is probed when a TPM Secure Partition is
>> discovered by the FF-A subsystem. It exposes APIs
>> used by the TPM CRB driver to send notifications to
>> the TPM.
>>
>> Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
>> ---
>>   drivers/char/tpm/Kconfig       |   9 +
>>   drivers/char/tpm/Makefile      |   1 +
>>   drivers/char/tpm/tpm_ffa_crb.c | 310 +++++++++++++++++++++++++++++++++
>>   drivers/char/tpm/tpm_ffa_crb.h |  30 ++++
>>   4 files changed, 350 insertions(+)
>>   create mode 100644 drivers/char/tpm/tpm_ffa_crb.c
>>   create mode 100644 drivers/char/tpm/tpm_ffa_crb.h
>>
>> diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
>> index 0fc9a510e059..af5ba7c63927 100644
>> --- a/drivers/char/tpm/Kconfig
>> +++ b/drivers/char/tpm/Kconfig
>> @@ -210,6 +210,15 @@ config TCG_CRB
>>   	  from within Linux.  To compile this driver as a module, choose
>>   	  M here; the module will be called tpm_crb.
>>   
>> +config TCG_ARM_FFA_CRB
>> +	tristate "TPM CRB over Arm FF-A Transport"
>> +	depends on ARM_FFA_TRANSPORT
>> +	default y if (TCG_CRB && ARM_FFA_TRANSPORT)
>> +	help
>> +	  If the Arm FF-A transport is used to access the TPM say Yes.
>> +	  To compile this driver as a module, choose M here; the module
>> +	  will be called tpm_ffa_crb.
>> +
>>   config TCG_VTPM_PROXY
>>   	tristate "VTPM Proxy Interface"
>>   	depends on TCG_TPM
>> diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
>> index 9bb142c75243..21f2eb5a485e 100644
>> --- a/drivers/char/tpm/Makefile
>> +++ b/drivers/char/tpm/Makefile
>> @@ -42,5 +42,6 @@ obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o
>>   obj-$(CONFIG_TCG_TIS_ST33ZP24) += st33zp24/
>>   obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
>>   obj-$(CONFIG_TCG_CRB) += tpm_crb.o
>> +obj-$(CONFIG_TCG_ARM_FFA_CRB) += tpm_ffa_crb.o
>>   obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
>>   obj-$(CONFIG_TCG_FTPM_TEE) += tpm_ftpm_tee.o
>> diff --git a/drivers/char/tpm/tpm_ffa_crb.c b/drivers/char/tpm/tpm_ffa_crb.c
>> new file mode 100644
>> index 000000000000..56bd77864a47
>> --- /dev/null
>> +++ b/drivers/char/tpm/tpm_ffa_crb.c
>> @@ -0,0 +1,310 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (C) 2024 Arm Ltd.
>> + *
>> + * Maintained by: <tpmdd-devel@lists.sourceforge.net>
>> + *
>> + * This device driver implements the TPM CRB start method
>> + * as defined in the TPM Service Command Response Buffer
>> + * Interface Over FF-A (DEN0138).
>> + */
>> +
>> +#define pr_fmt(fmt) "FFA_CRB: " fmt
>> +
>> +#include <linux/arm_ffa.h>
>> +#include "tpm_ffa_crb.h"
>> +
>> +/* TPM service function status codes */
>> +#define FFA_CRB_OK			0x05000001
>> +#define FFA_CRB_OK_RESULTS_RETURNED	0x05000002
>> +#define FFA_CRB_NOFUNC			0x8e000001
>> +#define FFA_CRB_NOTSUP			0x8e000002
>> +#define FFA_CRB_INVARG			0x8e000005
>> +#define FFA_CRB_INV_CRB_CTRL_DATA	0x8e000006
>> +#define FFA_CRB_ALREADY			0x8e000009
>> +#define FFA_CRB_DENIED			0x8e00000a
>> +#define FFA_CRB_NOMEM			0x8e00000b
>> +
>> +#define FFA_CRB_VERSION_MAJOR	1
>> +#define FFA_CRB_VERSION_MINOR	0
>> +
>> +/* version encoding */
>> +#define FFA_CRB_MAJOR_VERSION_MASK  GENMASK(30, 16)
>> +#define FFA_CRB_MINOR_VERSION_MASK  GENMASK(15, 0)
>> +#define FFA_CRB_MAJOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_MAJOR_VERSION_MASK, (x))))
>> +#define FFA_CRB_MINOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_MINOR_VERSION_MASK, (x))))
>> +
>> +/*
>> + * Normal world sends requests with FFA_MSG_SEND_DIRECT_REQ and
>> + * responses are returned with FFA_MSG_SEND_DIRECT_RESP for normal
>> + * messages.
>> + *
>> + * All requests with FFA_MSG_SEND_DIRECT_REQ and FFA_MSG_SEND_DIRECT_RESP
>> + * are using the AArch32 SMC calling convention with register usage as
>> + * defined in FF-A specification:
>> + * w0:    Function ID (0x8400006F or 0x84000070)
>> + * w1:    Source/Destination IDs
>> + * w2:    Reserved (MBZ)
>> + * w3-w7: Implementation defined, free to be used below
>> + */
>> +
>> +/*
>> + * Returns the version of the interface that is available
>> + * Call register usage:
>> + * w3:    Not used (MBZ)
>> + * w4:    TPM service function ID, FFA_CRB_GET_INTERFACE_VERSION
>> + * w5-w7: Reserved (MBZ)
>> + *
>> + * Return register usage:
>> + * w3:    Not used (MBZ)
>> + * w4:    TPM service function status
>> + * w5:    TPM service interface version
>> + *        Bits[31:16]: major version
>> + *        Bits[15:0]: minor version
>> + * w6-w7: Reserved (MBZ)
>> + *
>> + * Possible function status codes in register w4:
>> + *     CRB_FFA_OK_RESULTS_RETURNED: The version of the interface has been
>> + *                                  returned.
>> + */
>> +#define FFA_CRB_GET_INTERFACE_VERSION 0x0f000001
>> +
>> +/*
>> + * Return information on a given feature of the TPM service
>> + * Call register usage:
>> + * w3:    Not used (MBZ)
>> + * w4:    TPM service function ID, FFA_CRB_START
>> + * w5:    Start function qualifier
>> + *            Bits[31:8] (MBZ)
>> + *            Bits[7:0]
>> + *              0: Notifies TPM that a command is ready to be processed
>> + *              1: Notifies TPM that a locality request is ready to be processed
>> + * w6:    TPM locality, one of 0..4
>> + *            -If the start function qualifier is 0, identifies the locality
>> + *             from where the command originated.
>> + *            -If the start function qualifier is 1, identifies the locality
>> + *             of the locality request
>> + * w6-w7: Reserved (MBZ)
>> + *
>> + * Return register usage:
>> + * w3:    Not used (MBZ)
>> + * w4:    TPM service function status
>> + * w5-w7: Reserved (MBZ)
>> + *
>> + * Possible function status codes in register w4:
>> + *     FFA_CRB_OK: the TPM service has been notified successfully
>> + *     FFA_CRB_INVARG: one or more arguments are not valid
>> + *     FFA_CRB_INV_CRB_CTRL_DATA: CRB control data or locality control
>> + *         data at the given TPM locality is not valid
>> + *     FFA_CRB_DENIED: the TPM has previously disabled locality requests and
>> + *         command processing at the given locality
>> + */
>> +#define FFA_CRB_START 0x0f000201
>> +
>> +struct ffa_crb {
>> +	struct ffa_device *ffa_dev;
>> +	u16 major_version;
>> +	u16 minor_version;
>> +	struct mutex msg_data_lock;
>> +	struct ffa_send_direct_data direct_msg_data;
>> +};
>> +
>> +static struct ffa_crb *ffa_crb;
>> +
>> +static int ffa_crb_to_linux_errno(int errno)
>> +{
>> +	int rc;
>> +
>> +	switch (errno) {
>> +	case FFA_CRB_OK:
>> +		rc = 0;
>> +		break;
>> +	case FFA_CRB_OK_RESULTS_RETURNED:
>> +		rc = 0;
>> +		break;
>> +	case FFA_CRB_NOFUNC:
>> +		rc = -ENOENT;
>> +		break;
>> +	case FFA_CRB_NOTSUP:
>> +		rc = -EPERM;
>> +		break;
>> +	case FFA_CRB_INVARG:
>> +		rc = -EINVAL;
>> +		break;
>> +	case FFA_CRB_INV_CRB_CTRL_DATA:
>> +		rc = -ENOEXEC;
>> +		break;
>> +	case FFA_CRB_ALREADY:
>> +		rc = -EEXIST;
>> +		break;
>> +	case FFA_CRB_DENIED:
>> +		rc = -EACCES;
>> +		break;
>> +	case FFA_CRB_NOMEM:
>> +		rc = -ENOMEM;
>> +		break;
>> +	default:
>> +		rc = -EINVAL;
>> +	}
>> +
>> +	return rc;
>> +}
>> +
>> +int ffa_crb_init(void)
>> +{
>> +	if (ffa_crb == NULL)
>> +		return -ENOENT;
>> +
>> +	if (IS_ERR_VALUE(ffa_crb))
>> +		return -ENODEV;
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(ffa_crb_init);
>> +
>> +static int __ffa_crb_send_recieve(unsigned long func_id,
>> +		unsigned long a0, unsigned long a1, unsigned long a2)
>> +{
>> +	int ret;
>> +	const struct ffa_msg_ops *msg_ops;
>> +
>> +	if (ffa_crb == NULL)
>> +		return -ENOENT;
>> +
>> +	msg_ops = ffa_crb->ffa_dev->ops->msg_ops;
>> +
>> +	memset(&ffa_crb->direct_msg_data, 0x00,
>> +			sizeof(struct ffa_send_direct_data));
>> +
>> +	ffa_crb->direct_msg_data.data1 = func_id;
>> +	ffa_crb->direct_msg_data.data2 = a0;
>> +	ffa_crb->direct_msg_data.data3 = a1;
>> +	ffa_crb->direct_msg_data.data4 = a2;
>> +
>> +	ret = msg_ops->sync_send_receive(ffa_crb->ffa_dev,
>> +			&ffa_crb->direct_msg_data);
>> +	if (!ret)
>> +		ret = ffa_crb_to_linux_errno(ffa_crb->direct_msg_data.data1);
>> +
>> +	return ret;
>> +}
>> +
>> +int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor)
>> +{
>> +	int rc;
>> +
>> +	if (ffa_crb == NULL)
>> +		return -ENOENT;
>> +
>> +	if (IS_ERR_VALUE(ffa_crb))
>> +		return -ENODEV;
>> +
>> +	if (major == NULL || minor == NULL)
>> +		return -EINVAL;
>> +
>> +	guard(mutex)(&ffa_crb->msg_data_lock);
>> +
>> +	rc = __ffa_crb_send_recieve(FFA_CRB_GET_INTERFACE_VERSION, 0x00, 0x00, 0x00);
>> +	if (!rc) {
>> +		*major = FFA_CRB_MAJOR_VERSION(ffa_crb->direct_msg_data.data2);
>> +		*minor = FFA_CRB_MINOR_VERSION(ffa_crb->direct_msg_data.data2);
>> +	}
>> +
>> +	return rc;
>> +}
>> +EXPORT_SYMBOL_GPL(ffa_crb_get_interface_version);
>> +
>> +int ffa_crb_start(int request_type, int locality)
>> +{
>> +	if (ffa_crb == NULL)
>> +		return -ENOENT;
>> +
>> +	if (IS_ERR_VALUE(ffa_crb))
>> +		return -ENODEV;
>> +
>> +	guard(mutex)(&ffa_crb->msg_data_lock);
>> +
>> +	return __ffa_crb_send_recieve(FFA_CRB_START, request_type, locality, 0x00);
>> +}
>> +EXPORT_SYMBOL_GPL(ffa_crb_start);
>> +
>> +static int ffa_crb_probe(struct ffa_device *ffa_dev)
>> +{
>> +	int rc;
>> +	struct ffa_crb *p;
>> +
>> +	/* only one instance of a TPM partition is supported */
>> +	if (ffa_crb && !IS_ERR_VALUE(ffa_crb))
>> +		return -EEXIST;
>> +
>> +	ffa_crb = ERR_PTR(-ENODEV); // set ffa_crb so we can detect probe failure
>> +
>> +	if (!ffa_partition_supports_direct_recv(ffa_dev)) {
>> +		pr_err("TPM partition doesn't support direct message receive.\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	p = kzalloc(sizeof(*ffa_crb), GFP_KERNEL);
>> +	if (!p)
>> +		return -ENOMEM;
>> +	ffa_crb = p;
>> +
>> +	mutex_init(&ffa_crb->msg_data_lock);
>> +	ffa_crb->ffa_dev = ffa_dev;
>> +	ffa_dev_set_drvdata(ffa_dev, ffa_crb);
>> +
>> +	/* if TPM is aarch32 use 32-bit SMCs */
>> +	if (!ffa_partition_check_property(ffa_dev, FFA_PARTITION_AARCH64_EXEC))
>> +		ffa_dev->ops->msg_ops->mode_32bit_set(ffa_dev);
>> +
>> +	/* verify compatibility of TPM service version number */
>> +	rc = ffa_crb_get_interface_version(&ffa_crb->major_version,
>> +			&ffa_crb->minor_version);
>> +	if (rc) {
>> +		pr_err("failed to get crb interface version. rc:%d", rc);
>> +		goto out;
>> +	}
>> +
>> +	pr_info("ABI version %u.%u", ffa_crb->major_version,
>> +		ffa_crb->minor_version);
>> +
>> +	if ((ffa_crb->major_version != FFA_CRB_VERSION_MAJOR) ||
>> +	    (ffa_crb->minor_version < FFA_CRB_VERSION_MINOR)) {
>> +		pr_err("Incompatible ABI version");
>> +		goto out;
>> +	}
>> +
>> +	return 0;
>> +
>> +out:
>> +	kfree(ffa_crb);
>> +	ffa_crb = ERR_PTR(-ENODEV);
>> +	return -EINVAL;
>> +}
>> +
>> +static void ffa_crb_remove(struct ffa_device *ffa_dev)
>> +{
>> +	kfree(ffa_crb);
>> +	ffa_crb = NULL;
>> +}
>> +
>> +static const struct ffa_device_id ffa_crb_device_id[] = {
>> +	/* 17b862a4-1806-4faf-86b3-089a58353861 */
>> +	{ UUID_INIT(0x17b862a4, 0x1806, 0x4faf,
>> +		    0x86, 0xb3, 0x08, 0x9a, 0x58, 0x35, 0x38, 0x61) },
>> +	{}
>> +};
>> +
>> +static struct ffa_driver ffa_crb_driver = {
>> +	.name = "ffa-crb",
>> +	.probe = ffa_crb_probe,
>> +	.remove = ffa_crb_remove,
>> +	.id_table = ffa_crb_device_id,
>> +};
>> +
>> +module_ffa_driver(ffa_crb_driver);
>> +
>> +MODULE_AUTHOR("Arm");
>> +MODULE_DESCRIPTION("FFA CRB driver");
>> +MODULE_VERSION("1.0");
>> +MODULE_LICENSE("GPL");
>> diff --git a/drivers/char/tpm/tpm_ffa_crb.h b/drivers/char/tpm/tpm_ffa_crb.h
>> new file mode 100644
>> index 000000000000..42327d285165
>> --- /dev/null
>> +++ b/drivers/char/tpm/tpm_ffa_crb.h
>> @@ -0,0 +1,30 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only */
>> +/*
>> + * Copyright (C) 2024 Arm Ltd.
>> + *
>> + * Authors:
>> + * Stuart Yoder <stuart.yoder@arm.com>
>> + *
>> + * Maintained by: <tpmdd-devel@lists.sourceforge.net>
>> + *
>> + * This device driver implements the TPM CRB start method
>> + * as defined in the TPM Service Command Response Buffer
>> + * Interface Over FF-A (DEN0138).
>> + */
>> +#ifndef _FFA_CRB_H
>> +#define _FFA_CRB_H
>> +
>> +#if IS_ENABLED(CONFIG_TCG_ARM_FFA_CRB)
>> +int ffa_crb_init(void);
>> +int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor);
>> +int ffa_crb_start(int request_type, int locality);
>> +#else
>> +static inline int ffa_crb_init(void) { return 0; }
>> +static inline int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor) { return 0; }
>> +static inline int ffa_crb_start(int request_type, int locality) { return 0; }
>> +#endif
>> +
>> +#define FFA_CRB_START_TYPE_COMMAND 0
>> +#define FFA_CRB_START_TYPE_LOCALITY_REQUEST 1
>> +
>> +#endif
>> -- 
>> 2.34.1
>>
>>
> 
> tpm_crb_ffa_*

I had renamed the source file to be tpm_ffa_crb.c based on your
previous feedback.  It would be good to be consistent.  Would
you prefer:

tpm_crb_ffa_*
or
tpm_ffa_crb_*

Thanks,
Stuart

Re: [PATCH v2 1/5] tpm_crb: implement driver compliant to CRB over FF-A

[Jarkko Sakkinen]

On Thu, Feb 13, 2025 at 04:22:44PM -0600, Stuart Yoder wrote:
> 
> 
> On 2/13/25 4:14 PM, Jarkko Sakkinen wrote:
> > On Wed, Feb 12, 2025 at 04:05:44PM -0600, Stuart Yoder wrote:
> > > The Arm specification TPM Service CRB over FF-A specification
> > > defines the FF-A messages to interact with a CRB-based TPM
> > > implemented as an FF-A secure partition.
> > > 
> > > Spec URL:
> > > https://developer.arm.com/documentation/den0138/latest/
> > > 
> > > This driver is probed when a TPM Secure Partition is
> > > discovered by the FF-A subsystem. It exposes APIs
> > > used by the TPM CRB driver to send notifications to
> > > the TPM.
> > > 
> > > Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
> > > ---
> > >   drivers/char/tpm/Kconfig       |   9 +
> > >   drivers/char/tpm/Makefile      |   1 +
> > >   drivers/char/tpm/tpm_ffa_crb.c | 310 +++++++++++++++++++++++++++++++++
> > >   drivers/char/tpm/tpm_ffa_crb.h |  30 ++++
> > >   4 files changed, 350 insertions(+)
> > >   create mode 100644 drivers/char/tpm/tpm_ffa_crb.c
> > >   create mode 100644 drivers/char/tpm/tpm_ffa_crb.h
> > > 
> > > diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
> > > index 0fc9a510e059..af5ba7c63927 100644
> > > --- a/drivers/char/tpm/Kconfig
> > > +++ b/drivers/char/tpm/Kconfig
> > > @@ -210,6 +210,15 @@ config TCG_CRB
> > >   	  from within Linux.  To compile this driver as a module, choose
> > >   	  M here; the module will be called tpm_crb.
> > > +config TCG_ARM_FFA_CRB
> > > +	tristate "TPM CRB over Arm FF-A Transport"
> > > +	depends on ARM_FFA_TRANSPORT
> > > +	default y if (TCG_CRB && ARM_FFA_TRANSPORT)
> > > +	help
> > > +	  If the Arm FF-A transport is used to access the TPM say Yes.
> > > +	  To compile this driver as a module, choose M here; the module
> > > +	  will be called tpm_ffa_crb.
> > > +
> > >   config TCG_VTPM_PROXY
> > >   	tristate "VTPM Proxy Interface"
> > >   	depends on TCG_TPM
> > > diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
> > > index 9bb142c75243..21f2eb5a485e 100644
> > > --- a/drivers/char/tpm/Makefile
> > > +++ b/drivers/char/tpm/Makefile
> > > @@ -42,5 +42,6 @@ obj-$(CONFIG_TCG_IBMVTPM) += tpm_ibmvtpm.o
> > >   obj-$(CONFIG_TCG_TIS_ST33ZP24) += st33zp24/
> > >   obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
> > >   obj-$(CONFIG_TCG_CRB) += tpm_crb.o
> > > +obj-$(CONFIG_TCG_ARM_FFA_CRB) += tpm_ffa_crb.o
> > >   obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
> > >   obj-$(CONFIG_TCG_FTPM_TEE) += tpm_ftpm_tee.o
> > > diff --git a/drivers/char/tpm/tpm_ffa_crb.c b/drivers/char/tpm/tpm_ffa_crb.c
> > > new file mode 100644
> > > index 000000000000..56bd77864a47
> > > --- /dev/null
> > > +++ b/drivers/char/tpm/tpm_ffa_crb.c
> > > @@ -0,0 +1,310 @@
> > > +// SPDX-License-Identifier: GPL-2.0-only
> > > +/*
> > > + * Copyright (C) 2024 Arm Ltd.
> > > + *
> > > + * Maintained by: <tpmdd-devel@lists.sourceforge.net>
> > > + *
> > > + * This device driver implements the TPM CRB start method
> > > + * as defined in the TPM Service Command Response Buffer
> > > + * Interface Over FF-A (DEN0138).
> > > + */
> > > +
> > > +#define pr_fmt(fmt) "FFA_CRB: " fmt
> > > +
> > > +#include <linux/arm_ffa.h>
> > > +#include "tpm_ffa_crb.h"
> > > +
> > > +/* TPM service function status codes */
> > > +#define FFA_CRB_OK			0x05000001
> > > +#define FFA_CRB_OK_RESULTS_RETURNED	0x05000002
> > > +#define FFA_CRB_NOFUNC			0x8e000001
> > > +#define FFA_CRB_NOTSUP			0x8e000002
> > > +#define FFA_CRB_INVARG			0x8e000005
> > > +#define FFA_CRB_INV_CRB_CTRL_DATA	0x8e000006
> > > +#define FFA_CRB_ALREADY			0x8e000009
> > > +#define FFA_CRB_DENIED			0x8e00000a
> > > +#define FFA_CRB_NOMEM			0x8e00000b
> > > +
> > > +#define FFA_CRB_VERSION_MAJOR	1
> > > +#define FFA_CRB_VERSION_MINOR	0
> > > +
> > > +/* version encoding */
> > > +#define FFA_CRB_MAJOR_VERSION_MASK  GENMASK(30, 16)
> > > +#define FFA_CRB_MINOR_VERSION_MASK  GENMASK(15, 0)
> > > +#define FFA_CRB_MAJOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_MAJOR_VERSION_MASK, (x))))
> > > +#define FFA_CRB_MINOR_VERSION(x)    ((u16)(FIELD_GET(FFA_CRB_MINOR_VERSION_MASK, (x))))
> > > +
> > > +/*
> > > + * Normal world sends requests with FFA_MSG_SEND_DIRECT_REQ and
> > > + * responses are returned with FFA_MSG_SEND_DIRECT_RESP for normal
> > > + * messages.
> > > + *
> > > + * All requests with FFA_MSG_SEND_DIRECT_REQ and FFA_MSG_SEND_DIRECT_RESP
> > > + * are using the AArch32 SMC calling convention with register usage as
> > > + * defined in FF-A specification:
> > > + * w0:    Function ID (0x8400006F or 0x84000070)
> > > + * w1:    Source/Destination IDs
> > > + * w2:    Reserved (MBZ)
> > > + * w3-w7: Implementation defined, free to be used below
> > > + */
> > > +
> > > +/*
> > > + * Returns the version of the interface that is available
> > > + * Call register usage:
> > > + * w3:    Not used (MBZ)
> > > + * w4:    TPM service function ID, FFA_CRB_GET_INTERFACE_VERSION
> > > + * w5-w7: Reserved (MBZ)
> > > + *
> > > + * Return register usage:
> > > + * w3:    Not used (MBZ)
> > > + * w4:    TPM service function status
> > > + * w5:    TPM service interface version
> > > + *        Bits[31:16]: major version
> > > + *        Bits[15:0]: minor version
> > > + * w6-w7: Reserved (MBZ)
> > > + *
> > > + * Possible function status codes in register w4:
> > > + *     CRB_FFA_OK_RESULTS_RETURNED: The version of the interface has been
> > > + *                                  returned.
> > > + */
> > > +#define FFA_CRB_GET_INTERFACE_VERSION 0x0f000001
> > > +
> > > +/*
> > > + * Return information on a given feature of the TPM service
> > > + * Call register usage:
> > > + * w3:    Not used (MBZ)
> > > + * w4:    TPM service function ID, FFA_CRB_START
> > > + * w5:    Start function qualifier
> > > + *            Bits[31:8] (MBZ)
> > > + *            Bits[7:0]
> > > + *              0: Notifies TPM that a command is ready to be processed
> > > + *              1: Notifies TPM that a locality request is ready to be processed
> > > + * w6:    TPM locality, one of 0..4
> > > + *            -If the start function qualifier is 0, identifies the locality
> > > + *             from where the command originated.
> > > + *            -If the start function qualifier is 1, identifies the locality
> > > + *             of the locality request
> > > + * w6-w7: Reserved (MBZ)
> > > + *
> > > + * Return register usage:
> > > + * w3:    Not used (MBZ)
> > > + * w4:    TPM service function status
> > > + * w5-w7: Reserved (MBZ)
> > > + *
> > > + * Possible function status codes in register w4:
> > > + *     FFA_CRB_OK: the TPM service has been notified successfully
> > > + *     FFA_CRB_INVARG: one or more arguments are not valid
> > > + *     FFA_CRB_INV_CRB_CTRL_DATA: CRB control data or locality control
> > > + *         data at the given TPM locality is not valid
> > > + *     FFA_CRB_DENIED: the TPM has previously disabled locality requests and
> > > + *         command processing at the given locality
> > > + */
> > > +#define FFA_CRB_START 0x0f000201
> > > +
> > > +struct ffa_crb {
> > > +	struct ffa_device *ffa_dev;
> > > +	u16 major_version;
> > > +	u16 minor_version;
> > > +	struct mutex msg_data_lock;
> > > +	struct ffa_send_direct_data direct_msg_data;
> > > +};
> > > +
> > > +static struct ffa_crb *ffa_crb;
> > > +
> > > +static int ffa_crb_to_linux_errno(int errno)
> > > +{
> > > +	int rc;
> > > +
> > > +	switch (errno) {
> > > +	case FFA_CRB_OK:
> > > +		rc = 0;
> > > +		break;
> > > +	case FFA_CRB_OK_RESULTS_RETURNED:
> > > +		rc = 0;
> > > +		break;
> > > +	case FFA_CRB_NOFUNC:
> > > +		rc = -ENOENT;
> > > +		break;
> > > +	case FFA_CRB_NOTSUP:
> > > +		rc = -EPERM;
> > > +		break;
> > > +	case FFA_CRB_INVARG:
> > > +		rc = -EINVAL;
> > > +		break;
> > > +	case FFA_CRB_INV_CRB_CTRL_DATA:
> > > +		rc = -ENOEXEC;
> > > +		break;
> > > +	case FFA_CRB_ALREADY:
> > > +		rc = -EEXIST;
> > > +		break;
> > > +	case FFA_CRB_DENIED:
> > > +		rc = -EACCES;
> > > +		break;
> > > +	case FFA_CRB_NOMEM:
> > > +		rc = -ENOMEM;
> > > +		break;
> > > +	default:
> > > +		rc = -EINVAL;
> > > +	}
> > > +
> > > +	return rc;
> > > +}
> > > +
> > > +int ffa_crb_init(void)
> > > +{
> > > +	if (ffa_crb == NULL)
> > > +		return -ENOENT;
> > > +
> > > +	if (IS_ERR_VALUE(ffa_crb))
> > > +		return -ENODEV;
> > > +
> > > +	return 0;
> > > +}
> > > +EXPORT_SYMBOL_GPL(ffa_crb_init);
> > > +
> > > +static int __ffa_crb_send_recieve(unsigned long func_id,
> > > +		unsigned long a0, unsigned long a1, unsigned long a2)
> > > +{
> > > +	int ret;
> > > +	const struct ffa_msg_ops *msg_ops;
> > > +
> > > +	if (ffa_crb == NULL)
> > > +		return -ENOENT;
> > > +
> > > +	msg_ops = ffa_crb->ffa_dev->ops->msg_ops;
> > > +
> > > +	memset(&ffa_crb->direct_msg_data, 0x00,
> > > +			sizeof(struct ffa_send_direct_data));
> > > +
> > > +	ffa_crb->direct_msg_data.data1 = func_id;
> > > +	ffa_crb->direct_msg_data.data2 = a0;
> > > +	ffa_crb->direct_msg_data.data3 = a1;
> > > +	ffa_crb->direct_msg_data.data4 = a2;
> > > +
> > > +	ret = msg_ops->sync_send_receive(ffa_crb->ffa_dev,
> > > +			&ffa_crb->direct_msg_data);
> > > +	if (!ret)
> > > +		ret = ffa_crb_to_linux_errno(ffa_crb->direct_msg_data.data1);
> > > +
> > > +	return ret;
> > > +}
> > > +
> > > +int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor)
> > > +{
> > > +	int rc;
> > > +
> > > +	if (ffa_crb == NULL)
> > > +		return -ENOENT;
> > > +
> > > +	if (IS_ERR_VALUE(ffa_crb))
> > > +		return -ENODEV;
> > > +
> > > +	if (major == NULL || minor == NULL)
> > > +		return -EINVAL;
> > > +
> > > +	guard(mutex)(&ffa_crb->msg_data_lock);
> > > +
> > > +	rc = __ffa_crb_send_recieve(FFA_CRB_GET_INTERFACE_VERSION, 0x00, 0x00, 0x00);
> > > +	if (!rc) {
> > > +		*major = FFA_CRB_MAJOR_VERSION(ffa_crb->direct_msg_data.data2);
> > > +		*minor = FFA_CRB_MINOR_VERSION(ffa_crb->direct_msg_data.data2);
> > > +	}
> > > +
> > > +	return rc;
> > > +}
> > > +EXPORT_SYMBOL_GPL(ffa_crb_get_interface_version);
> > > +
> > > +int ffa_crb_start(int request_type, int locality)
> > > +{
> > > +	if (ffa_crb == NULL)
> > > +		return -ENOENT;
> > > +
> > > +	if (IS_ERR_VALUE(ffa_crb))
> > > +		return -ENODEV;
> > > +
> > > +	guard(mutex)(&ffa_crb->msg_data_lock);
> > > +
> > > +	return __ffa_crb_send_recieve(FFA_CRB_START, request_type, locality, 0x00);
> > > +}
> > > +EXPORT_SYMBOL_GPL(ffa_crb_start);
> > > +
> > > +static int ffa_crb_probe(struct ffa_device *ffa_dev)
> > > +{
> > > +	int rc;
> > > +	struct ffa_crb *p;
> > > +
> > > +	/* only one instance of a TPM partition is supported */
> > > +	if (ffa_crb && !IS_ERR_VALUE(ffa_crb))
> > > +		return -EEXIST;
> > > +
> > > +	ffa_crb = ERR_PTR(-ENODEV); // set ffa_crb so we can detect probe failure
> > > +
> > > +	if (!ffa_partition_supports_direct_recv(ffa_dev)) {
> > > +		pr_err("TPM partition doesn't support direct message receive.\n");
> > > +		return -EINVAL;
> > > +	}
> > > +
> > > +	p = kzalloc(sizeof(*ffa_crb), GFP_KERNEL);
> > > +	if (!p)
> > > +		return -ENOMEM;
> > > +	ffa_crb = p;
> > > +
> > > +	mutex_init(&ffa_crb->msg_data_lock);
> > > +	ffa_crb->ffa_dev = ffa_dev;
> > > +	ffa_dev_set_drvdata(ffa_dev, ffa_crb);
> > > +
> > > +	/* if TPM is aarch32 use 32-bit SMCs */
> > > +	if (!ffa_partition_check_property(ffa_dev, FFA_PARTITION_AARCH64_EXEC))
> > > +		ffa_dev->ops->msg_ops->mode_32bit_set(ffa_dev);
> > > +
> > > +	/* verify compatibility of TPM service version number */
> > > +	rc = ffa_crb_get_interface_version(&ffa_crb->major_version,
> > > +			&ffa_crb->minor_version);
> > > +	if (rc) {
> > > +		pr_err("failed to get crb interface version. rc:%d", rc);
> > > +		goto out;
> > > +	}
> > > +
> > > +	pr_info("ABI version %u.%u", ffa_crb->major_version,
> > > +		ffa_crb->minor_version);
> > > +
> > > +	if ((ffa_crb->major_version != FFA_CRB_VERSION_MAJOR) ||
> > > +	    (ffa_crb->minor_version < FFA_CRB_VERSION_MINOR)) {
> > > +		pr_err("Incompatible ABI version");
> > > +		goto out;
> > > +	}
> > > +
> > > +	return 0;
> > > +
> > > +out:
> > > +	kfree(ffa_crb);
> > > +	ffa_crb = ERR_PTR(-ENODEV);
> > > +	return -EINVAL;
> > > +}
> > > +
> > > +static void ffa_crb_remove(struct ffa_device *ffa_dev)
> > > +{
> > > +	kfree(ffa_crb);
> > > +	ffa_crb = NULL;
> > > +}
> > > +
> > > +static const struct ffa_device_id ffa_crb_device_id[] = {
> > > +	/* 17b862a4-1806-4faf-86b3-089a58353861 */
> > > +	{ UUID_INIT(0x17b862a4, 0x1806, 0x4faf,
> > > +		    0x86, 0xb3, 0x08, 0x9a, 0x58, 0x35, 0x38, 0x61) },
> > > +	{}
> > > +};
> > > +
> > > +static struct ffa_driver ffa_crb_driver = {
> > > +	.name = "ffa-crb",
> > > +	.probe = ffa_crb_probe,
> > > +	.remove = ffa_crb_remove,
> > > +	.id_table = ffa_crb_device_id,
> > > +};
> > > +
> > > +module_ffa_driver(ffa_crb_driver);
> > > +
> > > +MODULE_AUTHOR("Arm");
> > > +MODULE_DESCRIPTION("FFA CRB driver");
> > > +MODULE_VERSION("1.0");
> > > +MODULE_LICENSE("GPL");
> > > diff --git a/drivers/char/tpm/tpm_ffa_crb.h b/drivers/char/tpm/tpm_ffa_crb.h
> > > new file mode 100644
> > > index 000000000000..42327d285165
> > > --- /dev/null
> > > +++ b/drivers/char/tpm/tpm_ffa_crb.h
> > > @@ -0,0 +1,30 @@
> > > +/* SPDX-License-Identifier: GPL-2.0-only */
> > > +/*
> > > + * Copyright (C) 2024 Arm Ltd.
> > > + *
> > > + * Authors:
> > > + * Stuart Yoder <stuart.yoder@arm.com>
> > > + *
> > > + * Maintained by: <tpmdd-devel@lists.sourceforge.net>
> > > + *
> > > + * This device driver implements the TPM CRB start method
> > > + * as defined in the TPM Service Command Response Buffer
> > > + * Interface Over FF-A (DEN0138).
> > > + */
> > > +#ifndef _FFA_CRB_H
> > > +#define _FFA_CRB_H
> > > +
> > > +#if IS_ENABLED(CONFIG_TCG_ARM_FFA_CRB)
> > > +int ffa_crb_init(void);
> > > +int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor);
> > > +int ffa_crb_start(int request_type, int locality);
> > > +#else
> > > +static inline int ffa_crb_init(void) { return 0; }
> > > +static inline int ffa_crb_get_interface_version(uint16_t *major, uint16_t *minor) { return 0; }
> > > +static inline int ffa_crb_start(int request_type, int locality) { return 0; }
> > > +#endif
> > > +
> > > +#define FFA_CRB_START_TYPE_COMMAND 0
> > > +#define FFA_CRB_START_TYPE_LOCALITY_REQUEST 1
> > > +
> > > +#endif
> > > -- 
> > > 2.34.1
> > > 
> > > 
> > 
> > tpm_crb_ffa_*
> 
> I had renamed the source file to be tpm_ffa_crb.c based on your
> previous feedback.  It would be good to be consistent.  Would
> you prefer:
> 
> tpm_crb_ffa_*
> or
> tpm_ffa_crb_*

I made a mistake and apologize for that!

I thought about tpm_crb_ffa_* but wrote in misorder.

Sorry about this!

BR, Jarkko

Re: [PATCH v2 1/5] tpm_crb: implement driver compliant to CRB over FF-A

[kernel test robot]

Hi Stuart,

kernel test robot noticed the following build warnings:

[auto build test WARNING on char-misc/char-misc-testing]
[also build test WARNING on char-misc/char-misc-next char-misc/char-misc-linus rafael-pm/linux-next rafael-pm/bleeding-edge linus/master v6.14-rc2 next-20250214]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Stuart-Yoder/tpm_crb-implement-driver-compliant-to-CRB-over-FF-A/20250213-060938
base:   char-misc/char-misc-testing
patch link:    https://lore.kernel.org/r/20250212220548.400447-2-stuart.yoder%40arm.com
patch subject: [PATCH v2 1/5] tpm_crb: implement driver compliant to CRB over FF-A
config: arm64-randconfig-r073-20250214 (https://download.01.org/0day-ci/archive/20250216/202502160801.zzYlGtHn-lkp@intel.com/config)
compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202502160801.zzYlGtHn-lkp@intel.com/

smatch warnings:
drivers/char/tpm/tpm_ffa_crb.c:272 ffa_crb_probe() warn: unsigned 'ffa_crb->minor_version' is never less than zero.

vim +272 drivers/char/tpm/tpm_ffa_crb.c

   230	
   231	static int ffa_crb_probe(struct ffa_device *ffa_dev)
   232	{
   233		int rc;
   234		struct ffa_crb *p;
   235	
   236		/* only one instance of a TPM partition is supported */
   237		if (ffa_crb && !IS_ERR_VALUE(ffa_crb))
   238			return -EEXIST;
   239	
   240		ffa_crb = ERR_PTR(-ENODEV); // set ffa_crb so we can detect probe failure
   241	
   242		if (!ffa_partition_supports_direct_recv(ffa_dev)) {
   243			pr_err("TPM partition doesn't support direct message receive.\n");
   244			return -EINVAL;
   245		}
   246	
   247		p = kzalloc(sizeof(*ffa_crb), GFP_KERNEL);
   248		if (!p)
   249			return -ENOMEM;
   250		ffa_crb = p;
   251	
   252		mutex_init(&ffa_crb->msg_data_lock);
   253		ffa_crb->ffa_dev = ffa_dev;
   254		ffa_dev_set_drvdata(ffa_dev, ffa_crb);
   255	
   256		/* if TPM is aarch32 use 32-bit SMCs */
   257		if (!ffa_partition_check_property(ffa_dev, FFA_PARTITION_AARCH64_EXEC))
   258			ffa_dev->ops->msg_ops->mode_32bit_set(ffa_dev);
   259	
   260		/* verify compatibility of TPM service version number */
   261		rc = ffa_crb_get_interface_version(&ffa_crb->major_version,
   262				&ffa_crb->minor_version);
   263		if (rc) {
   264			pr_err("failed to get crb interface version. rc:%d", rc);
   265			goto out;
   266		}
   267	
   268		pr_info("ABI version %u.%u", ffa_crb->major_version,
   269			ffa_crb->minor_version);
   270	
   271		if ((ffa_crb->major_version != FFA_CRB_VERSION_MAJOR) ||
 > 272		    (ffa_crb->minor_version < FFA_CRB_VERSION_MINOR)) {
   273			pr_err("Incompatible ABI version");
   274			goto out;
   275		}
   276	
   277		return 0;
   278	
   279	out:
   280		kfree(ffa_crb);
   281		ffa_crb = ERR_PTR(-ENODEV);
   282		return -EINVAL;
   283	}
   284	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

[PATCH v2 2/5] tpm_crb: refactor check for idle support into TPM into inline function

[Stuart Yoder]

Refactor the two checks for whether the TPM supports idle into a single
inline function.

Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
---
 drivers/char/tpm/tpm_crb.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
index ea085b14ab7c..87d69e990249 100644
--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c
@@ -115,6 +115,16 @@ struct tpm2_crb_pluton {
 	u64 reply_addr;
 };
 
+static inline bool does_tpm_support_idle(u32 start_method)
+{
+	if ((start_method == ACPI_TPM2_START_METHOD) ||
+	    (start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
+	    (start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
+		return false;
+	else
+		return true;
+}
+
 static bool crb_wait_for_reg_32(u32 __iomem *reg, u32 mask, u32 value,
 				unsigned long timeout)
 {
@@ -173,9 +183,7 @@ static int __crb_go_idle(struct device *dev, struct crb_priv *priv)
 {
 	int rc;
 
-	if ((priv->sm == ACPI_TPM2_START_METHOD) ||
-	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
-	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
+	if (!does_tpm_support_idle(priv->sm))
 		return 0;
 
 	iowrite32(CRB_CTRL_REQ_GO_IDLE, &priv->regs_t->ctrl_req);
@@ -222,9 +230,7 @@ static int __crb_cmd_ready(struct device *dev, struct crb_priv *priv)
 {
 	int rc;
 
-	if ((priv->sm == ACPI_TPM2_START_METHOD) ||
-	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
-	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
+	if (!does_tpm_support_idle(priv->sm))
 		return 0;
 
 	iowrite32(CRB_CTRL_REQ_CMD_READY, &priv->regs_t->ctrl_req);
-- 
2.34.1

Re: [PATCH v2 2/5] tpm_crb: refactor check for idle support into TPM into inline function

[Jarkko Sakkinen]

On Wed, Feb 12, 2025 at 04:05:45PM -0600, Stuart Yoder wrote:
> Refactor the two checks for whether the TPM supports idle into a single
> inline function.
> 
> Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
> ---
>  drivers/char/tpm/tpm_crb.c | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
> index ea085b14ab7c..87d69e990249 100644
> --- a/drivers/char/tpm/tpm_crb.c
> +++ b/drivers/char/tpm/tpm_crb.c
> @@ -115,6 +115,16 @@ struct tpm2_crb_pluton {
>  	u64 reply_addr;
>  };
>  
> +static inline bool does_tpm_support_idle(u32 start_method)
> +{
> +	if ((start_method == ACPI_TPM2_START_METHOD) ||
> +	    (start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
> +	    (start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
> +		return false;
> +	else
> +		return true;
> +}
> +

I think we could also prefix tpm_crb stuff with tpm_crb_* for the sake
of easier grepping etc.

So I'd propose this to be called as: tpm_crb_has_idle()

>  static bool crb_wait_for_reg_32(u32 __iomem *reg, u32 mask, u32 value,
>  				unsigned long timeout)
>  {
> @@ -173,9 +183,7 @@ static int __crb_go_idle(struct device *dev, struct crb_priv *priv)
>  {
>  	int rc;
>  
> -	if ((priv->sm == ACPI_TPM2_START_METHOD) ||
> -	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
> -	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
> +	if (!does_tpm_support_idle(priv->sm))
>  		return 0;
>  
>  	iowrite32(CRB_CTRL_REQ_GO_IDLE, &priv->regs_t->ctrl_req);
> @@ -222,9 +230,7 @@ static int __crb_cmd_ready(struct device *dev, struct crb_priv *priv)
>  {
>  	int rc;
>  
> -	if ((priv->sm == ACPI_TPM2_START_METHOD) ||
> -	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
> -	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
> +	if (!does_tpm_support_idle(priv->sm))
>  		return 0;
>  
>  	iowrite32(CRB_CTRL_REQ_CMD_READY, &priv->regs_t->ctrl_req);
> -- 
> 2.34.1
> 

BR, Jarkko

Re: [PATCH v2 2/5] tpm_crb: refactor check for idle support into TPM into inline function

[Stuart Yoder]

On 2/13/25 4:13 PM, Jarkko Sakkinen wrote:
> On Wed, Feb 12, 2025 at 04:05:45PM -0600, Stuart Yoder wrote:
>> Refactor the two checks for whether the TPM supports idle into a single
>> inline function.
>>
>> Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
>> ---
>>   drivers/char/tpm/tpm_crb.c | 18 ++++++++++++------
>>   1 file changed, 12 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
>> index ea085b14ab7c..87d69e990249 100644
>> --- a/drivers/char/tpm/tpm_crb.c
>> +++ b/drivers/char/tpm/tpm_crb.c
>> @@ -115,6 +115,16 @@ struct tpm2_crb_pluton {
>>   	u64 reply_addr;
>>   };
>>   
>> +static inline bool does_tpm_support_idle(u32 start_method)
>> +{
>> +	if ((start_method == ACPI_TPM2_START_METHOD) ||
>> +	    (start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
>> +	    (start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
>> +		return false;
>> +	else
>> +		return true;
>> +}
>> +
> 
> I think we could also prefix tpm_crb stuff with tpm_crb_* for the sake
> of easier grepping etc.
> 
> So I'd propose this to be called as: tpm_crb_has_idle()

Ack.

Stuart

[PATCH v2 3/5] ACPICA: add start method for Arm FF-A

[Stuart Yoder]

Add TPM start method for Arm FF-A defined in the TCG ACPI
specification v1.4.

Link: https://github.com/acpica/acpica/pull/1000
Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
---
 include/acpi/actbl3.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/acpi/actbl3.h b/include/acpi/actbl3.h
index 5cd755143b7d..a97b1dbab975 100644
--- a/include/acpi/actbl3.h
+++ b/include/acpi/actbl3.h
@@ -466,6 +466,7 @@ struct acpi_tpm2_phy {
 #define ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC       11	/* V1.2 Rev 8 */
 #define ACPI_TPM2_RESERVED                          12
 #define ACPI_TPM2_COMMAND_BUFFER_WITH_PLUTON        13
+#define ACPI_TPM2_CRB_WITH_ARM_FFA                  15
 
 /* Optional trailer appears after any start_method subtables */
 
-- 
2.34.1

[PATCH v2 4/5] tpm_crb: add support for the Arm FF-A start method

[Stuart Yoder]

The TCG ACPI spec v1.4 defines a start method for the
TPMs implemented with the Arm CRB over FF-A ABI.

Add support for the FF-A start method, and use interfaces
provided by the ffa_crb driver to interact with the
FF-A based TPM.

Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
---
 drivers/char/tpm/tpm_crb.c | 65 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 64 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
index 87d69e990249..4b6b13b8ea27 100644
--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c
@@ -19,6 +19,7 @@
 #ifdef CONFIG_ARM64
 #include <linux/arm-smccc.h>
 #endif
+#include "tpm_ffa_crb.h"
 #include "tpm.h"
 
 #define ACPI_SIG_TPM2 "TPM2"
@@ -100,6 +101,8 @@ struct crb_priv {
 	u32 smc_func_id;
 	u32 __iomem *pluton_start_addr;
 	u32 __iomem *pluton_reply_addr;
+	u8 ffa_flags;
+	u8 ffa_attributes;
 };
 
 struct tpm2_crb_smc {
@@ -110,6 +113,14 @@ struct tpm2_crb_smc {
 	u32 smc_func_id;
 };
 
+/* CRB over FFA start method parameters in TCG2 ACPI table */
+struct tpm2_crb_ffa {
+	u8 flags;
+	u8 attributes;
+	u16 partition_id;
+	u8 reserved[8];
+};
+
 struct tpm2_crb_pluton {
 	u64 start_addr;
 	u64 reply_addr;
@@ -119,7 +130,8 @@ static inline bool does_tpm_support_idle(u32 start_method)
 {
 	if ((start_method == ACPI_TPM2_START_METHOD) ||
 	    (start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD) ||
-	    (start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC))
+	    (start_method == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC) ||
+	    (start_method == ACPI_TPM2_CRB_WITH_ARM_FFA))
 		return false;
 	else
 		return true;
@@ -261,6 +273,7 @@ static int crb_cmd_ready(struct tpm_chip *chip)
 static int __crb_request_locality(struct device *dev,
 				  struct crb_priv *priv, int loc)
 {
+	int rc;
 	u32 value = CRB_LOC_STATE_LOC_ASSIGNED |
 		    CRB_LOC_STATE_TPM_REG_VALID_STS;
 
@@ -268,6 +281,13 @@ static int __crb_request_locality(struct device *dev,
 		return 0;
 
 	iowrite32(CRB_LOC_CTRL_REQUEST_ACCESS, &priv->regs_h->loc_ctrl);
+
+	if (priv->sm == ACPI_TPM2_CRB_WITH_ARM_FFA) {
+		rc = ffa_crb_start(FFA_CRB_START_TYPE_LOCALITY_REQUEST, loc);
+		if (rc)
+			return rc;
+	}
+
 	if (!crb_wait_for_reg_32(&priv->regs_h->loc_state, value, value,
 				 TPM2_TIMEOUT_C)) {
 		dev_warn(dev, "TPM_LOC_STATE_x.requestAccess timed out\n");
@@ -287,6 +307,7 @@ static int crb_request_locality(struct tpm_chip *chip, int loc)
 static int __crb_relinquish_locality(struct device *dev,
 				     struct crb_priv *priv, int loc)
 {
+	int rc;
 	u32 mask = CRB_LOC_STATE_LOC_ASSIGNED |
 		   CRB_LOC_STATE_TPM_REG_VALID_STS;
 	u32 value = CRB_LOC_STATE_TPM_REG_VALID_STS;
@@ -295,6 +316,13 @@ static int __crb_relinquish_locality(struct device *dev,
 		return 0;
 
 	iowrite32(CRB_LOC_CTRL_RELINQUISH, &priv->regs_h->loc_ctrl);
+
+	if (priv->sm == ACPI_TPM2_CRB_WITH_ARM_FFA) {
+		rc = ffa_crb_start(FFA_CRB_START_TYPE_LOCALITY_REQUEST, loc);
+		if (rc)
+			return rc;
+	}
+
 	if (!crb_wait_for_reg_32(&priv->regs_h->loc_state, mask, value,
 				 TPM2_TIMEOUT_C)) {
 		dev_warn(dev, "TPM_LOC_STATE_x.Relinquish timed out\n");
@@ -443,6 +471,11 @@ static int crb_send(struct tpm_chip *chip, u8 *buf, size_t len)
 		rc = tpm_crb_smc_start(&chip->dev, priv->smc_func_id);
 	}
 
+	if (priv->sm == ACPI_TPM2_CRB_WITH_ARM_FFA) {
+		iowrite32(CRB_START_INVOKE, &priv->regs_t->ctrl_start);
+		rc = ffa_crb_start(FFA_CRB_START_TYPE_COMMAND, chip->locality);
+	}
+
 	if (rc)
 		return rc;
 
@@ -451,6 +484,7 @@ static int crb_send(struct tpm_chip *chip, u8 *buf, size_t len)
 
 static void crb_cancel(struct tpm_chip *chip)
 {
+	int rc;
 	struct crb_priv *priv = dev_get_drvdata(&chip->dev);
 
 	iowrite32(CRB_CANCEL_INVOKE, &priv->regs_t->ctrl_cancel);
@@ -459,6 +493,12 @@ static void crb_cancel(struct tpm_chip *chip)
 	    (priv->sm == ACPI_TPM2_COMMAND_BUFFER_WITH_START_METHOD)) &&
 	     crb_do_acpi_start(chip))
 		dev_err(&chip->dev, "ACPI Start failed\n");
+
+	if (priv->sm == ACPI_TPM2_CRB_WITH_ARM_FFA) {
+		rc = ffa_crb_start(FFA_CRB_START_TYPE_COMMAND, chip->locality);
+		if (rc)
+			dev_err(&chip->dev, "FF-A Start failed\n");
+	}
 }
 
 static bool crb_req_canceled(struct tpm_chip *chip, u8 status)
@@ -616,6 +656,7 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
 	 * stuff that puts the control area outside the ACPI IO region.
 	 */
 	if ((priv->sm == ACPI_TPM2_COMMAND_BUFFER) ||
+	    (priv->sm == ACPI_TPM2_CRB_WITH_ARM_FFA) ||
 	    (priv->sm == ACPI_TPM2_MEMORY_MAPPED)) {
 		if (iores &&
 		    buf->control_address == iores->start +
@@ -737,6 +778,7 @@ static int crb_acpi_add(struct acpi_device *device)
 	struct tpm_chip *chip;
 	struct device *dev = &device->dev;
 	struct tpm2_crb_smc *crb_smc;
+	struct tpm2_crb_ffa *crb_ffa;
 	struct tpm2_crb_pluton *crb_pluton;
 	acpi_status status;
 	u32 sm;
@@ -775,6 +817,27 @@ static int crb_acpi_add(struct acpi_device *device)
 		priv->smc_func_id = crb_smc->smc_func_id;
 	}
 
+	if (sm == ACPI_TPM2_CRB_WITH_ARM_FFA) {
+		if (buf->header.length < (sizeof(*buf) + sizeof(*crb_ffa))) {
+			dev_err(dev,
+				FW_BUG "TPM2 ACPI table has wrong size %u for start method type %d\n",
+				buf->header.length,
+				ACPI_TPM2_CRB_WITH_ARM_FFA);
+			rc = -EINVAL;
+			goto out;
+		}
+		crb_ffa = ACPI_ADD_PTR(struct tpm2_crb_ffa, buf, sizeof(*buf));
+		priv->ffa_flags = crb_ffa->flags;
+		priv->ffa_attributes = crb_ffa->attributes;
+		rc = ffa_crb_init();
+		if (rc) {
+			if (rc == -ENOENT) {  // FF-A driver is not available yet
+				rc = -EPROBE_DEFER;
+			}
+			goto out;
+		}
+	}
+
 	if (sm == ACPI_TPM2_COMMAND_BUFFER_WITH_PLUTON) {
 		if (buf->header.length < (sizeof(*buf) + sizeof(*crb_pluton))) {
 			dev_err(dev,
-- 
2.34.1

[PATCH v2 5/5] Documentation: tpm: add documentation for the CRB FF-A interface

[Stuart Yoder]

Add documentation providing details of how the CRB driver interacts
with FF-A.

Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
---
 Documentation/security/tpm/tpm_ffa_crb.rst | 65 ++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 Documentation/security/tpm/tpm_ffa_crb.rst

diff --git a/Documentation/security/tpm/tpm_ffa_crb.rst b/Documentation/security/tpm/tpm_ffa_crb.rst
new file mode 100644
index 000000000000..c70f8904a93d
--- /dev/null
+++ b/Documentation/security/tpm/tpm_ffa_crb.rst
@@ -0,0 +1,65 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========================
+TPM CRB over FF-A Driver
+========================
+
+The TPM Command Response Buffer (CRB) interface is a standard TPM interface
+defined in the TCG PC Client Platform TPM Profile (PTP) Specification [1]_.
+The CRB provides a structured set of control registers a client uses when
+interacting with a TPM as well as a data buffer for storing TPM commands and
+responses. A CRB interface can be implemented in:
+
+- hardware registers in a discrete TPM chip
+
+- in memory for a TPM running in isolated environment where shared memory
+  allows a client to interact with the TPM
+
+The Firmware Framework for Arm A-profile (FF-A) [2]_ is a specification
+that defines interfaces and protocols for the following purposes:
+
+- Compartmentalize firmware into software partitions that run in the Arm
+  Secure world environment (also know as TrustZone)
+
+- Provide a standard interface for software components in the Non-secure
+  state, for example OS and Hypervisors, to communicate with this firmware.
+
+A TPM can be implemented as an FF-A secure service.  This could be a firmware
+TPM or could potentially be a TPM service that acts as a proxy to a discrete
+TPM chip. An FF-A based TPM abstracts hardware details (e.g. bus controller
+and chip selects) away from the OS and can protect locality 4 from access
+by an OS.  The TCG-defined CRB interface is used by clients to interact
+with the TPM service.
+
+The Arm TPM Service Command Response Buffer Interface Over FF-A [3]_
+specification defines FF-A messages that can be used by a client to signal
+when updates have been made to the CRB.
+
+How the Linux CRB driver interacts with FF-A is summarized below:
+
+- The tpm_ffa_crb driver registers with the FF-A subsystem in the kernel
+  with an architected TPM service UUID defined in the CRB over FF-A spec.
+
+- If a TPM service is discovered by FF-A, the probe() function in the
+  tpm_ffa_crb driver runs, and the driver initializes.
+
+- The probing and initialization of the Linux CRB driver is triggered
+  by the discovery of a TPM advertised via ACPI.  The CRB driver can
+  detect the type of TPM through the ACPI 'start' method.  The start
+  method for Arm FF-A was defined in TCG ACPI v1.4 [4]_.
+
+- When the CRB driver performs its normal functions such as signaling 'start'
+  and locality request/relinquish it invokes the ffa_crb_start() funnction
+  in the tpm_ffa_crb driver which handles the FF-A messaging to the TPM.
+
+References
+==========
+
+.. [1] **TCG PC Client Platform TPM Profile (PTP) Specification**
+   https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
+.. [2] **Arm Firmware Framework for Arm A-profile (FF-A)**
+   https://developer.arm.com/documentation/den0077/latest/
+.. [3] **Arm TPM Service Command Response Buffer Interface Over FF-A**
+   https://developer.arm.com/documentation/den0138/latest/
+.. [4] **TCG ACPI Specification**
+   https://trustedcomputinggroup.org/resource/tcg-acpi-specification/
-- 
2.34.1

Re: [PATCH v2 5/5] Documentation: tpm: add documentation for the CRB FF-A interface

[Jarkko Sakkinen]

On Wed, Feb 12, 2025 at 04:05:48PM -0600, Stuart Yoder wrote:
> Add documentation providing details of how the CRB driver interacts
> with FF-A.
> 
> Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
> ---
>  Documentation/security/tpm/tpm_ffa_crb.rst | 65 ++++++++++++++++++++++
>  1 file changed, 65 insertions(+)
>  create mode 100644 Documentation/security/tpm/tpm_ffa_crb.rst
> 
> diff --git a/Documentation/security/tpm/tpm_ffa_crb.rst b/Documentation/security/tpm/tpm_ffa_crb.rst
> new file mode 100644
> index 000000000000..c70f8904a93d
> --- /dev/null
> +++ b/Documentation/security/tpm/tpm_ffa_crb.rst
> @@ -0,0 +1,65 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +========================
> +TPM CRB over FF-A Driver
> +========================
> +
> +The TPM Command Response Buffer (CRB) interface is a standard TPM interface
> +defined in the TCG PC Client Platform TPM Profile (PTP) Specification [1]_.
> +The CRB provides a structured set of control registers a client uses when
> +interacting with a TPM as well as a data buffer for storing TPM commands and
> +responses. A CRB interface can be implemented in:
> +
> +- hardware registers in a discrete TPM chip
> +
> +- in memory for a TPM running in isolated environment where shared memory
> +  allows a client to interact with the TPM
> +
> +The Firmware Framework for Arm A-profile (FF-A) [2]_ is a specification
> +that defines interfaces and protocols for the following purposes:
> +
> +- Compartmentalize firmware into software partitions that run in the Arm
> +  Secure world environment (also know as TrustZone)

Does that also cover ARM CCA? Just a question (not a review question).

> +
> +- Provide a standard interface for software components in the Non-secure
> +  state, for example OS and Hypervisors, to communicate with this firmware.
> +
> +A TPM can be implemented as an FF-A secure service.  This could be a firmware
> +TPM or could potentially be a TPM service that acts as a proxy to a discrete
> +TPM chip. An FF-A based TPM abstracts hardware details (e.g. bus controller
> +and chip selects) away from the OS and can protect locality 4 from access
> +by an OS.  The TCG-defined CRB interface is used by clients to interact
> +with the TPM service.
> +
> +The Arm TPM Service Command Response Buffer Interface Over FF-A [3]_
> +specification defines FF-A messages that can be used by a client to signal
> +when updates have been made to the CRB.
> +
> +How the Linux CRB driver interacts with FF-A is summarized below:
> +
> +- The tpm_ffa_crb driver registers with the FF-A subsystem in the kernel
> +  with an architected TPM service UUID defined in the CRB over FF-A spec.
> +
> +- If a TPM service is discovered by FF-A, the probe() function in the
> +  tpm_ffa_crb driver runs, and the driver initializes.
> +
> +- The probing and initialization of the Linux CRB driver is triggered
> +  by the discovery of a TPM advertised via ACPI.  The CRB driver can
> +  detect the type of TPM through the ACPI 'start' method.  The start
> +  method for Arm FF-A was defined in TCG ACPI v1.4 [4]_.
> +
> +- When the CRB driver performs its normal functions such as signaling 'start'
> +  and locality request/relinquish it invokes the ffa_crb_start() funnction
> +  in the tpm_ffa_crb driver which handles the FF-A messaging to the TPM.
> +
> +References
> +==========
> +
> +.. [1] **TCG PC Client Platform TPM Profile (PTP) Specification**
> +   https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
> +.. [2] **Arm Firmware Framework for Arm A-profile (FF-A)**
> +   https://developer.arm.com/documentation/den0077/latest/
> +.. [3] **Arm TPM Service Command Response Buffer Interface Over FF-A**
> +   https://developer.arm.com/documentation/den0138/latest/
> +.. [4] **TCG ACPI Specification**
> +   https://trustedcomputinggroup.org/resource/tcg-acpi-specification/
> -- 
> 2.34.1


Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

BR, Jarkko

Re: [PATCH v2 5/5] Documentation: tpm: add documentation for the CRB FF-A interface

[Stuart Yoder]

On 2/13/25 4:11 PM, Jarkko Sakkinen wrote:
> On Wed, Feb 12, 2025 at 04:05:48PM -0600, Stuart Yoder wrote:
>> Add documentation providing details of how the CRB driver interacts
>> with FF-A.
>>
>> Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
>> ---
>>   Documentation/security/tpm/tpm_ffa_crb.rst | 65 ++++++++++++++++++++++
>>   1 file changed, 65 insertions(+)
>>   create mode 100644 Documentation/security/tpm/tpm_ffa_crb.rst
>>
>> diff --git a/Documentation/security/tpm/tpm_ffa_crb.rst b/Documentation/security/tpm/tpm_ffa_crb.rst
>> new file mode 100644
>> index 000000000000..c70f8904a93d
>> --- /dev/null
>> +++ b/Documentation/security/tpm/tpm_ffa_crb.rst
>> @@ -0,0 +1,65 @@
>> +.. SPDX-License-Identifier: GPL-2.0
>> +
>> +========================
>> +TPM CRB over FF-A Driver
>> +========================
>> +
>> +The TPM Command Response Buffer (CRB) interface is a standard TPM interface
>> +defined in the TCG PC Client Platform TPM Profile (PTP) Specification [1]_.
>> +The CRB provides a structured set of control registers a client uses when
>> +interacting with a TPM as well as a data buffer for storing TPM commands and
>> +responses. A CRB interface can be implemented in:
>> +
>> +- hardware registers in a discrete TPM chip
>> +
>> +- in memory for a TPM running in isolated environment where shared memory
>> +  allows a client to interact with the TPM
>> +
>> +The Firmware Framework for Arm A-profile (FF-A) [2]_ is a specification
>> +that defines interfaces and protocols for the following purposes:
>> +
>> +- Compartmentalize firmware into software partitions that run in the Arm
>> +  Secure world environment (also know as TrustZone)
> 
> Does that also cover ARM CCA? Just a question (not a review question).

No, CCA is for confidential VMs which is a separate trusted execution
environment and FF-A is not used there.

Thanks,
Stuart

Re: [PATCH v2 5/5] Documentation: tpm: add documentation for the CRB FF-A interface

[Jarkko Sakkinen]

On Thu, Feb 13, 2025 at 04:17:56PM -0600, Stuart Yoder wrote:
> 
> 
> On 2/13/25 4:11 PM, Jarkko Sakkinen wrote:
> > On Wed, Feb 12, 2025 at 04:05:48PM -0600, Stuart Yoder wrote:
> > > Add documentation providing details of how the CRB driver interacts
> > > with FF-A.
> > > 
> > > Signed-off-by: Stuart Yoder <stuart.yoder@arm.com>
> > > ---
> > >   Documentation/security/tpm/tpm_ffa_crb.rst | 65 ++++++++++++++++++++++
> > >   1 file changed, 65 insertions(+)
> > >   create mode 100644 Documentation/security/tpm/tpm_ffa_crb.rst
> > > 
> > > diff --git a/Documentation/security/tpm/tpm_ffa_crb.rst b/Documentation/security/tpm/tpm_ffa_crb.rst
> > > new file mode 100644
> > > index 000000000000..c70f8904a93d
> > > --- /dev/null
> > > +++ b/Documentation/security/tpm/tpm_ffa_crb.rst
> > > @@ -0,0 +1,65 @@
> > > +.. SPDX-License-Identifier: GPL-2.0
> > > +
> > > +========================
> > > +TPM CRB over FF-A Driver
> > > +========================
> > > +
> > > +The TPM Command Response Buffer (CRB) interface is a standard TPM interface
> > > +defined in the TCG PC Client Platform TPM Profile (PTP) Specification [1]_.
> > > +The CRB provides a structured set of control registers a client uses when
> > > +interacting with a TPM as well as a data buffer for storing TPM commands and
> > > +responses. A CRB interface can be implemented in:
> > > +
> > > +- hardware registers in a discrete TPM chip
> > > +
> > > +- in memory for a TPM running in isolated environment where shared memory
> > > +  allows a client to interact with the TPM
> > > +
> > > +The Firmware Framework for Arm A-profile (FF-A) [2]_ is a specification
> > > +that defines interfaces and protocols for the following purposes:
> > > +
> > > +- Compartmentalize firmware into software partitions that run in the Arm
> > > +  Secure world environment (also know as TrustZone)
> > 
> > Does that also cover ARM CCA? Just a question (not a review question).
> 
> No, CCA is for confidential VMs which is a separate trusted execution
> environment and FF-A is not used there.

OK, cool, just plain interested :-)

> 
> Thanks,
> Stuart

BR, Jarkko