[PATCH v2 0/4] tpm: add support for sync send() and use it in ftpm and svsm drivers

[PATCH v2 0/4] tpm: add support for sync send() and use it in ftpm and svsm drivers

[Stefano Garzarella]

This series is a follow-up to the discussion we had about whether or not
to add send_recv() op in tpm_class_ops[1]. Much boilerplate code has
already been removed by Jarkko with commit 980a573621ea ("tpm: Make
chip->{status,cancel,req_canceled} opt"). With this series we try to
avoid also the temporary buffers needed between send() and recv() for
devices that do not support interrupts and provide a single operation
to send the command and receive the response on the same buffer like
tpm_ftpm_tee.

The biggest advantage for this approach is with tpm_ftpm_tee where we
remove the local buffer and extra memory copies. For tpm_svsm it does
not change much since we continue to use the pre-allocated buffer,
to avoid making an allocation for each command.

Introduce a new flag (TPM_CHIP_FLAG_SYNC) to support synchronous send().
If that flag is set by the driver, tpm_try_transmit() will use the send()
callback to send the command and receive the response on the same buffer
synchronously. In that case send() return the number of bytes of the
response on success, or -errno on failure.

This series is based on "[PATCH v6 0/4] Enlightened vTPM support for SVSM
on SEV-SNP" [2], so if we want to apply this series first, we just have to
remove a hunk in the first patch and the whole last patch.

I removed Jens' T-b and Sumit R-b from RFC/v1 since we changed the code a
bit, so I kindly ask if you can test/review again.
I left some questions on patch 1.

Thanks,
Stefano

Changelog
- v1 -> v2
  - changed title since we removed send_recv() op
  - implemented TPM_CHIP_FLAG_SYNC idea [Jarkko]
  - removed Jens' T-b

- RFC -> v1: https://lore.kernel.org/linux-integrity/20250320152433.144083-1-sgarzare@redhat.com/
  - added Jens' T-b on ftpm driver
  - removed last patch since [2] is not yet merged and will require a new version

- RFC: https://lore.kernel.org/linux-integrity/20250311100130.42169-1-sgarzare@redhat.com/

[1] https://lore.kernel.org/linux-integrity/Z8sfiDEhsG6RATiQ@kernel.org/
[2] https://lore.kernel.org/linux-integrity/20250403100943.120738-1-sgarzare@redhat.com/

Stefano Garzarella (4):
  tpm: add buf_size parameter in the .send callback
  tpm: support devices with synchronous send()
  tpm/tpm_ftpm_tee: support TPM_CHIP_FLAG_SYNC
  tpm/tpm_svsm: support TPM_CHIP_FLAG_SYNC

 drivers/char/tpm/tpm_ftpm_tee.h      |  4 --
 include/linux/tpm.h                  |  4 +-
 drivers/char/tpm/st33zp24/st33zp24.c |  2 +-
 drivers/char/tpm/tpm-interface.c     | 20 +++++++--
 drivers/char/tpm/tpm_atmel.c         |  3 +-
 drivers/char/tpm/tpm_crb.c           |  2 +-
 drivers/char/tpm/tpm_ftpm_tee.c      | 66 +++++++++-------------------
 drivers/char/tpm/tpm_i2c_atmel.c     |  3 +-
 drivers/char/tpm/tpm_i2c_infineon.c  |  3 +-
 drivers/char/tpm/tpm_i2c_nuvoton.c   |  3 +-
 drivers/char/tpm/tpm_ibmvtpm.c       |  6 ++-
 drivers/char/tpm/tpm_infineon.c      |  3 +-
 drivers/char/tpm/tpm_nsc.c           |  3 +-
 drivers/char/tpm/tpm_svsm.c          | 28 +++++-------
 drivers/char/tpm/tpm_tis_core.c      |  3 +-
 drivers/char/tpm/tpm_tis_i2c_cr50.c  |  6 ++-
 drivers/char/tpm/tpm_vtpm_proxy.c    |  4 +-
 drivers/char/tpm/xen-tpmfront.c      |  3 +-
 18 files changed, 81 insertions(+), 85 deletions(-)


base-commit: 92d2673cb03c16e47d7308dedad6ff3bc3d117ca
-- 
2.49.0

[PATCH v2 1/4] tpm: add buf_size parameter in the .send callback

[Stefano Garzarella]

From: Stefano Garzarella <sgarzare@redhat.com>

In preparation for the next commit, add a new `buf_size` parameter to
the `.send` callback in `tpm_class_ops` which contains the entire buffer
size. In this patch it is pretty much ignored by all drivers, but it will
be used in the next patch.

Also rename the previous parameter `len` to `cmd_len` in the
declaration to make it clear that it contains the length in bytes of the
command stored in the buffer. The semantics don't change and it can be
used as before by drivers. This is an optimization since the drivers
could get it from the header, but let's avoid duplicating code.

While we are here, resolve a checkpatch warning:
  WARNING: Unnecessary space before function pointer arguments
  #66: FILE: include/linux/tpm.h:90:
  +	int (*send) (struct tpm_chip *chip, u8 *buf, size_t cmd_len,

Suggested-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
I'm not sure about 3 things about this patch:

1. Since `buf_size` is pretty much ignored, is it better to merge this
   patch with the next one?
   I kept it separate because we touch all the drivers here, so I think
   it's better to have this change in a separate patch to make it clear
   that we are not touching anything in the drivers, but I'm open to
   merge it if you prefer.

2. I avoided changing the previous parameter in the drivers (`len` or
   `count`) to keep the changes minimal, but if you prefer I can use
   `cmd_len` everywhere.

3. Fix the checkpatch warning mentioned in the description.

Thanks,
Stefano
---
 include/linux/tpm.h                  | 3 ++-
 drivers/char/tpm/st33zp24/st33zp24.c | 2 +-
 drivers/char/tpm/tpm-interface.c     | 2 +-
 drivers/char/tpm/tpm_atmel.c         | 3 ++-
 drivers/char/tpm/tpm_crb.c           | 2 +-
 drivers/char/tpm/tpm_ftpm_tee.c      | 4 +++-
 drivers/char/tpm/tpm_i2c_atmel.c     | 3 ++-
 drivers/char/tpm/tpm_i2c_infineon.c  | 3 ++-
 drivers/char/tpm/tpm_i2c_nuvoton.c   | 3 ++-
 drivers/char/tpm/tpm_ibmvtpm.c       | 6 ++++--
 drivers/char/tpm/tpm_infineon.c      | 3 ++-
 drivers/char/tpm/tpm_nsc.c           | 3 ++-
 drivers/char/tpm/tpm_svsm.c          | 3 ++-
 drivers/char/tpm/tpm_tis_core.c      | 3 ++-
 drivers/char/tpm/tpm_tis_i2c_cr50.c  | 6 ++++--
 drivers/char/tpm/tpm_vtpm_proxy.c    | 4 +++-
 drivers/char/tpm/xen-tpmfront.c      | 3 ++-
 17 files changed, 37 insertions(+), 19 deletions(-)

diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 6c3125300c00..2e38edd5838c 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -87,7 +87,8 @@ struct tpm_class_ops {
 	const u8 req_complete_val;
 	bool (*req_canceled)(struct tpm_chip *chip, u8 status);
 	int (*recv) (struct tpm_chip *chip, u8 *buf, size_t len);
-	int (*send) (struct tpm_chip *chip, u8 *buf, size_t len);
+	int (*send)(struct tpm_chip *chip, u8 *buf, size_t cmd_len,
+		    size_t buf_size);
 	void (*cancel) (struct tpm_chip *chip);
 	u8 (*status) (struct tpm_chip *chip);
 	void (*update_timeouts)(struct tpm_chip *chip,
diff --git a/drivers/char/tpm/st33zp24/st33zp24.c b/drivers/char/tpm/st33zp24/st33zp24.c
index c0771980bc2f..3de68bca1740 100644
--- a/drivers/char/tpm/st33zp24/st33zp24.c
+++ b/drivers/char/tpm/st33zp24/st33zp24.c
@@ -300,7 +300,7 @@ static irqreturn_t tpm_ioserirq_handler(int irq, void *dev_id)
  * send TPM commands through the I2C bus.
  */
 static int st33zp24_send(struct tpm_chip *chip, unsigned char *buf,
-			 size_t len)
+			 size_t len, size_t buf_size)
 {
 	struct st33zp24_dev *tpm_dev = dev_get_drvdata(&chip->dev);
 	u32 status, i, size, ordinal;
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 8d7e4da6ed53..3b6ddcdb4051 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -106,7 +106,7 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, void *buf, size_t bufsiz)
 		return -E2BIG;
 	}
 
-	rc = chip->ops->send(chip, buf, count);
+	rc = chip->ops->send(chip, buf, count, bufsiz);
 	if (rc < 0) {
 		if (rc != -EPIPE)
 			dev_err(&chip->dev,
diff --git a/drivers/char/tpm/tpm_atmel.c b/drivers/char/tpm/tpm_atmel.c
index 54a0360a3c95..5733168bfc26 100644
--- a/drivers/char/tpm/tpm_atmel.c
+++ b/drivers/char/tpm/tpm_atmel.c
@@ -148,7 +148,8 @@ static int tpm_atml_recv(struct tpm_chip *chip, u8 *buf, size_t count)
 	return size;
 }
 
-static int tpm_atml_send(struct tpm_chip *chip, u8 *buf, size_t count)
+static int tpm_atml_send(struct tpm_chip *chip, u8 *buf, size_t count,
+			 size_t buf_size)
 {
 	struct tpm_atmel_priv *priv = dev_get_drvdata(&chip->dev);
 	int i;
diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
index 876edf2705ab..38f765a44a97 100644
--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c
@@ -426,7 +426,7 @@ static int tpm_crb_smc_start(struct device *dev, unsigned long func_id)
 }
 #endif
 
-static int crb_send(struct tpm_chip *chip, u8 *buf, size_t len)
+static int crb_send(struct tpm_chip *chip, u8 *buf, size_t len, size_t buf_size)
 {
 	struct crb_priv *priv = dev_get_drvdata(&chip->dev);
 	int rc = 0;
diff --git a/drivers/char/tpm/tpm_ftpm_tee.c b/drivers/char/tpm/tpm_ftpm_tee.c
index 53ba28ccd5d3..637cc8b6599e 100644
--- a/drivers/char/tpm/tpm_ftpm_tee.c
+++ b/drivers/char/tpm/tpm_ftpm_tee.c
@@ -64,12 +64,14 @@ static int ftpm_tee_tpm_op_recv(struct tpm_chip *chip, u8 *buf, size_t count)
  * @chip:	the tpm_chip description as specified in driver/char/tpm/tpm.h
  * @buf:	the buffer to send.
  * @len:	the number of bytes to send.
+ * @buf_size:	the size of the buffer.
  *
  * Return:
  *	In case of success, returns 0.
  *	On failure, -errno
  */
-static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t len)
+static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t len,
+				size_t buf_size)
 {
 	struct ftpm_tee_private *pvt_data = dev_get_drvdata(chip->dev.parent);
 	size_t resp_len;
diff --git a/drivers/char/tpm/tpm_i2c_atmel.c b/drivers/char/tpm/tpm_i2c_atmel.c
index d1d27fdfe523..572f97cb9e89 100644
--- a/drivers/char/tpm/tpm_i2c_atmel.c
+++ b/drivers/char/tpm/tpm_i2c_atmel.c
@@ -37,7 +37,8 @@ struct priv_data {
 	u8 buffer[sizeof(struct tpm_header) + 25];
 };
 
-static int i2c_atmel_send(struct tpm_chip *chip, u8 *buf, size_t len)
+static int i2c_atmel_send(struct tpm_chip *chip, u8 *buf, size_t len,
+			  size_t buf_size)
 {
 	struct priv_data *priv = dev_get_drvdata(&chip->dev);
 	struct i2c_client *client = to_i2c_client(chip->dev.parent);
diff --git a/drivers/char/tpm/tpm_i2c_infineon.c b/drivers/char/tpm/tpm_i2c_infineon.c
index 81d8a78dc655..25d6ae3a4cc1 100644
--- a/drivers/char/tpm/tpm_i2c_infineon.c
+++ b/drivers/char/tpm/tpm_i2c_infineon.c
@@ -514,7 +514,8 @@ static int tpm_tis_i2c_recv(struct tpm_chip *chip, u8 *buf, size_t count)
 	return size;
 }
 
-static int tpm_tis_i2c_send(struct tpm_chip *chip, u8 *buf, size_t len)
+static int tpm_tis_i2c_send(struct tpm_chip *chip, u8 *buf, size_t len,
+			    size_t buf_size)
 {
 	int rc, status;
 	ssize_t burstcnt;
diff --git a/drivers/char/tpm/tpm_i2c_nuvoton.c b/drivers/char/tpm/tpm_i2c_nuvoton.c
index 3c3ee5f551db..169078ce6ac4 100644
--- a/drivers/char/tpm/tpm_i2c_nuvoton.c
+++ b/drivers/char/tpm/tpm_i2c_nuvoton.c
@@ -350,7 +350,8 @@ static int i2c_nuvoton_recv(struct tpm_chip *chip, u8 *buf, size_t count)
  * tpm.c can skip polling for the data to be available as the interrupt is
  * waited for here
  */
-static int i2c_nuvoton_send(struct tpm_chip *chip, u8 *buf, size_t len)
+static int i2c_nuvoton_send(struct tpm_chip *chip, u8 *buf, size_t len,
+			    size_t buf_size)
 {
 	struct priv_data *priv = dev_get_drvdata(&chip->dev);
 	struct device *dev = chip->dev.parent;
diff --git a/drivers/char/tpm/tpm_ibmvtpm.c b/drivers/char/tpm/tpm_ibmvtpm.c
index 76d048f63d55..660a7f9da1d8 100644
--- a/drivers/char/tpm/tpm_ibmvtpm.c
+++ b/drivers/char/tpm/tpm_ibmvtpm.c
@@ -191,13 +191,15 @@ static int tpm_ibmvtpm_resume(struct device *dev)
  * tpm_ibmvtpm_send() - Send a TPM command
  * @chip:	tpm chip struct
  * @buf:	buffer contains data to send
- * @count:	size of buffer
+ * @count:	length of the command
+ * @buf_size:   size of the buffer
  *
  * Return:
  *   0 on success,
  *   -errno on error
  */
-static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
+static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count,
+			    size_t buf_size)
 {
 	struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
 	bool retry = true;
diff --git a/drivers/char/tpm/tpm_infineon.c b/drivers/char/tpm/tpm_infineon.c
index 2d2ae37153ba..7896fdacd156 100644
--- a/drivers/char/tpm/tpm_infineon.c
+++ b/drivers/char/tpm/tpm_infineon.c
@@ -312,7 +312,8 @@ static int tpm_inf_recv(struct tpm_chip *chip, u8 * buf, size_t count)
 	return -EIO;
 }
 
-static int tpm_inf_send(struct tpm_chip *chip, u8 * buf, size_t count)
+static int tpm_inf_send(struct tpm_chip *chip, u8 *buf, size_t count,
+			size_t buf_size)
 {
 	int i;
 	int ret;
diff --git a/drivers/char/tpm/tpm_nsc.c b/drivers/char/tpm/tpm_nsc.c
index 0f62bbc940da..12aedef3c50e 100644
--- a/drivers/char/tpm/tpm_nsc.c
+++ b/drivers/char/tpm/tpm_nsc.c
@@ -178,7 +178,8 @@ static int tpm_nsc_recv(struct tpm_chip *chip, u8 * buf, size_t count)
 	return size;
 }
 
-static int tpm_nsc_send(struct tpm_chip *chip, u8 * buf, size_t count)
+static int tpm_nsc_send(struct tpm_chip *chip, u8 *buf, size_t count,
+			size_t buf_size)
 {
 	struct tpm_nsc_priv *priv = dev_get_drvdata(&chip->dev);
 	u8 data;
diff --git a/drivers/char/tpm/tpm_svsm.c b/drivers/char/tpm/tpm_svsm.c
index b9242c9eab87..b8aa7eb567de 100644
--- a/drivers/char/tpm/tpm_svsm.c
+++ b/drivers/char/tpm/tpm_svsm.c
@@ -25,7 +25,8 @@ struct tpm_svsm_priv {
 	void *buffer;
 };
 
-static int tpm_svsm_send(struct tpm_chip *chip, u8 *buf, size_t len)
+static int tpm_svsm_send(struct tpm_chip *chip, u8 *buf, size_t len,
+			 size_t buf_size)
 {
 	struct tpm_svsm_priv *priv = dev_get_drvdata(&chip->dev);
 	int ret;
diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index ed0d3d8449b3..5641a73ce280 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -580,7 +580,8 @@ static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
 	return rc;
 }
 
-static int tpm_tis_send(struct tpm_chip *chip, u8 *buf, size_t len)
+static int tpm_tis_send(struct tpm_chip *chip, u8 *buf, size_t len,
+			size_t buf_size)
 {
 	int rc, irq;
 	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
diff --git a/drivers/char/tpm/tpm_tis_i2c_cr50.c b/drivers/char/tpm/tpm_tis_i2c_cr50.c
index 3b55a7b05c46..1914b368472d 100644
--- a/drivers/char/tpm/tpm_tis_i2c_cr50.c
+++ b/drivers/char/tpm/tpm_tis_i2c_cr50.c
@@ -546,13 +546,15 @@ static int tpm_cr50_i2c_tis_recv(struct tpm_chip *chip, u8 *buf, size_t buf_len)
  * tpm_cr50_i2c_tis_send() - TPM transmission callback.
  * @chip:	A TPM chip.
  * @buf:	Buffer to send.
- * @len:	Buffer length.
+ * @len:	Command length.
+ * @buf_size:	Buffer size.
  *
  * Return:
  * - 0:		Success.
  * - -errno:	A POSIX error code.
  */
-static int tpm_cr50_i2c_tis_send(struct tpm_chip *chip, u8 *buf, size_t len)
+static int tpm_cr50_i2c_tis_send(struct tpm_chip *chip, u8 *buf, size_t len,
+				 size_t buf_size)
 {
 	size_t burstcnt, limit, sent = 0;
 	u8 tpm_go[4] = { TPM_STS_GO };
diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c
index 8fe4a01eea12..beaa84428b49 100644
--- a/drivers/char/tpm/tpm_vtpm_proxy.c
+++ b/drivers/char/tpm/tpm_vtpm_proxy.c
@@ -322,11 +322,13 @@ static int vtpm_proxy_is_driver_command(struct tpm_chip *chip,
  * @chip: tpm chip to use
  * @buf: send buffer
  * @count: bytes to send
+ * @buf_size: size of the buffer
  *
  * Return:
  *      0 in case of success, negative error value otherwise.
  */
-static int vtpm_proxy_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t count)
+static int vtpm_proxy_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t count,
+				  size_t buf_size)
 {
 	struct proxy_dev *proxy_dev = dev_get_drvdata(&chip->dev);
 
diff --git a/drivers/char/tpm/xen-tpmfront.c b/drivers/char/tpm/xen-tpmfront.c
index 80cca3b83b22..66a4dbb4a4d8 100644
--- a/drivers/char/tpm/xen-tpmfront.c
+++ b/drivers/char/tpm/xen-tpmfront.c
@@ -131,7 +131,8 @@ static size_t shr_data_offset(struct vtpm_shared_page *shr)
 	return struct_size(shr, extra_pages, shr->nr_extra_pages);
 }
 
-static int vtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
+static int vtpm_send(struct tpm_chip *chip, u8 *buf, size_t count,
+		     size_t buf_size)
 {
 	struct tpm_private *priv = dev_get_drvdata(&chip->dev);
 	struct vtpm_shared_page *shr = priv->shr;
-- 
2.49.0

[PATCH v2 2/4] tpm: support devices with synchronous send()

[Stefano Garzarella]

From: Stefano Garzarella <sgarzare@redhat.com>

Some devices do not support interrupts and provide a single synchronous
operation to send the command and receive the response on the same buffer.

Currently, these types of drivers must use an internal buffer where they
temporarily store the response between .send() and recv() calls.

Introduce a new flag (TPM_CHIP_FLAG_SYNC) to support synchronous send().
If that flag is set by the driver, tpm_try_transmit() will use the send()
callback to send the command and receive the response on the same buffer
synchronously. In that case send() return the number of bytes of the
response on success, or -errno on failure.

Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
Suggested-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 include/linux/tpm.h              |  1 +
 drivers/char/tpm/tpm-interface.c | 18 +++++++++++++++---
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 2e38edd5838c..0e9746dc9d30 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -350,6 +350,7 @@ enum tpm_chip_flags {
 	TPM_CHIP_FLAG_SUSPENDED			= BIT(8),
 	TPM_CHIP_FLAG_HWRNG_DISABLED		= BIT(9),
 	TPM_CHIP_FLAG_DISABLE			= BIT(10),
+	TPM_CHIP_FLAG_SYNC			= BIT(11),
 };
 
 #define to_tpm_chip(d) container_of(d, struct tpm_chip, dev)
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 3b6ddcdb4051..9fbe84b5a131 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -114,8 +114,17 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, void *buf, size_t bufsiz)
 		return rc;
 	}
 
-	/* A sanity check. send() should just return zero on success e.g.
-	 * not the command length.
+	/* Synchronous devices return the response directly during the send()
+	 * call in the same buffer.
+	 */
+	if (chip->flags & TPM_CHIP_FLAG_SYNC) {
+		len = rc;
+		rc = 0;
+		goto out_send_sync;
+	}
+
+	/* A sanity check. send() of asynchronous devices should just return
+	 * zero on success e.g. not the command length.
 	 */
 	if (rc > 0) {
 		dev_warn(&chip->dev,
@@ -151,7 +160,10 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, void *buf, size_t bufsiz)
 	if (len < 0) {
 		rc = len;
 		dev_err(&chip->dev, "tpm_transmit: tpm_recv: error %d\n", rc);
-	} else if (len < TPM_HEADER_SIZE || len != be32_to_cpu(header->length))
+		return rc;
+	}
+out_send_sync:
+	if (len < TPM_HEADER_SIZE || len != be32_to_cpu(header->length))
 		rc = -EFAULT;
 
 	return rc ? rc : len;
-- 
2.49.0

[PATCH v2 3/4] tpm/tpm_ftpm_tee: support TPM_CHIP_FLAG_SYNC

[Stefano Garzarella]

From: Stefano Garzarella <sgarzare@redhat.com>

This driver does not support interrupts, and receiving the response is
synchronous with sending the command.

So we can set TPM_CHIP_FLAG_SYNC to support synchronous send() and
return responses in the same buffer used for commands. This way we
don't need the 4KB internal buffer used to cache the response before
.send() and .recv(). Also we don't need to implement recv() op.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
@Jens @Sumit can you test/review this patch again since we changed the
core a bit adding TPM_CHIP_FLAG_SYNC instead of send_recv() op?

Thanks,
Stefano

v2:
- set TPM_CHIP_FLAG_SYNC and support it in the new send()
- removed Jens' T-b
v1:
- added Jens' T-b
---
 drivers/char/tpm/tpm_ftpm_tee.h |  4 ---
 drivers/char/tpm/tpm_ftpm_tee.c | 64 ++++++++++-----------------------
 2 files changed, 19 insertions(+), 49 deletions(-)

diff --git a/drivers/char/tpm/tpm_ftpm_tee.h b/drivers/char/tpm/tpm_ftpm_tee.h
index e39903b7ea07..8d5c3f0d2879 100644
--- a/drivers/char/tpm/tpm_ftpm_tee.h
+++ b/drivers/char/tpm/tpm_ftpm_tee.h
@@ -22,16 +22,12 @@
  * struct ftpm_tee_private - fTPM's private data
  * @chip:     struct tpm_chip instance registered with tpm framework.
  * @session:  fTPM TA session identifier.
- * @resp_len: cached response buffer length.
- * @resp_buf: cached response buffer.
  * @ctx:      TEE context handler.
  * @shm:      Memory pool shared with fTPM TA in TEE.
  */
 struct ftpm_tee_private {
 	struct tpm_chip *chip;
 	u32 session;
-	size_t resp_len;
-	u8 resp_buf[MAX_RESPONSE_SIZE];
 	struct tee_context *ctx;
 	struct tee_shm *shm;
 };
diff --git a/drivers/char/tpm/tpm_ftpm_tee.c b/drivers/char/tpm/tpm_ftpm_tee.c
index 637cc8b6599e..b9adc040ca6d 100644
--- a/drivers/char/tpm/tpm_ftpm_tee.c
+++ b/drivers/char/tpm/tpm_ftpm_tee.c
@@ -31,46 +31,18 @@ static const uuid_t ftpm_ta_uuid =
 		  0x82, 0xCB, 0x34, 0x3F, 0xB7, 0xF3, 0x78, 0x96);
 
 /**
- * ftpm_tee_tpm_op_recv() - retrieve fTPM response.
- * @chip:	the tpm_chip description as specified in driver/char/tpm/tpm.h.
- * @buf:	the buffer to store data.
- * @count:	the number of bytes to read.
- *
- * Return:
- *	In case of success the number of bytes received.
- *	On failure, -errno.
- */
-static int ftpm_tee_tpm_op_recv(struct tpm_chip *chip, u8 *buf, size_t count)
-{
-	struct ftpm_tee_private *pvt_data = dev_get_drvdata(chip->dev.parent);
-	size_t len;
-
-	len = pvt_data->resp_len;
-	if (count < len) {
-		dev_err(&chip->dev,
-			"%s: Invalid size in recv: count=%zd, resp_len=%zd\n",
-			__func__, count, len);
-		return -EIO;
-	}
-
-	memcpy(buf, pvt_data->resp_buf, len);
-	pvt_data->resp_len = 0;
-
-	return len;
-}
-
-/**
- * ftpm_tee_tpm_op_send() - send TPM commands through the TEE shared memory.
+ * ftpm_tee_tpm_op_send() - send TPM commands through the TEE shared memory
+ * and retrieve the response.
  * @chip:	the tpm_chip description as specified in driver/char/tpm/tpm.h
- * @buf:	the buffer to send.
- * @len:	the number of bytes to send.
+ * @buf:	the buffer to send and to store the response.
+ * @cmd_len:	the number of bytes to send.
  * @buf_size:	the size of the buffer.
  *
  * Return:
- *	In case of success, returns 0.
+ *	In case of success, returns the number of bytes received.
  *	On failure, -errno
  */
-static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t len,
+static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t cmd_len,
 				size_t buf_size)
 {
 	struct ftpm_tee_private *pvt_data = dev_get_drvdata(chip->dev.parent);
@@ -82,16 +54,15 @@ static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t len,
 	struct tee_param command_params[4];
 	struct tee_shm *shm = pvt_data->shm;
 
-	if (len > MAX_COMMAND_SIZE) {
+	if (cmd_len > MAX_COMMAND_SIZE) {
 		dev_err(&chip->dev,
 			"%s: len=%zd exceeds MAX_COMMAND_SIZE supported by fTPM TA\n",
-			__func__, len);
+			__func__, cmd_len);
 		return -EIO;
 	}
 
 	memset(&transceive_args, 0, sizeof(transceive_args));
 	memset(command_params, 0, sizeof(command_params));
-	pvt_data->resp_len = 0;
 
 	/* Invoke FTPM_OPTEE_TA_SUBMIT_COMMAND function of fTPM TA */
 	transceive_args = (struct tee_ioctl_invoke_arg) {
@@ -105,7 +76,7 @@ static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t len,
 		.attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INPUT,
 		.u.memref = {
 			.shm = shm,
-			.size = len,
+			.size = cmd_len,
 			.shm_offs = 0,
 		},
 	};
@@ -117,7 +88,7 @@ static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t len,
 		return PTR_ERR(temp_buf);
 	}
 	memset(temp_buf, 0, (MAX_COMMAND_SIZE + MAX_RESPONSE_SIZE));
-	memcpy(temp_buf, buf, len);
+	memcpy(temp_buf, buf, cmd_len);
 
 	command_params[1] = (struct tee_param) {
 		.attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INOUT,
@@ -158,17 +129,20 @@ static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t len,
 			__func__, resp_len);
 		return -EIO;
 	}
+	if (resp_len > buf_size) {
+		dev_err(&chip->dev,
+			"%s: resp_len=%zd exceeds buf_size=%zd\n",
+			__func__, resp_len, buf_size);
+		return -EIO;
+	}
 
-	/* sanity checks look good, cache the response */
-	memcpy(pvt_data->resp_buf, temp_buf, resp_len);
-	pvt_data->resp_len = resp_len;
+	memcpy(buf, temp_buf, resp_len);
 
-	return 0;
+	return resp_len;
 }
 
 static const struct tpm_class_ops ftpm_tee_tpm_ops = {
 	.flags = TPM_OPS_AUTO_STARTUP,
-	.recv = ftpm_tee_tpm_op_recv,
 	.send = ftpm_tee_tpm_op_send,
 };
 
@@ -253,7 +227,7 @@ static int ftpm_tee_probe(struct device *dev)
 	}
 
 	pvt_data->chip = chip;
-	pvt_data->chip->flags |= TPM_CHIP_FLAG_TPM2;
+	pvt_data->chip->flags |= TPM_CHIP_FLAG_TPM2 | TPM_CHIP_FLAG_SYNC;
 
 	/* Create a character device for the fTPM */
 	rc = tpm_chip_register(pvt_data->chip);
-- 
2.49.0

[PATCH v2 4/4] tpm/tpm_svsm: support TPM_CHIP_FLAG_SYNC

[Stefano Garzarella]

From: Stefano Garzarella <sgarzare@redhat.com>

This driver does not support interrupts, and receiving the response is
synchronous with sending the command.

So we can set TPM_CHIP_FLAG_SYNC to support synchronous send() and
return responses in the same buffer used for commands. This way we
don't need to implement recv() op.

Keep using the same pre-allocated buffer to avoid having to allocate
it for each command. We need the buffer to have the header required by
the SVSM protocol and the command contiguous in memory.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 drivers/char/tpm/tpm_svsm.c | 27 +++++++++++----------------
 1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/drivers/char/tpm/tpm_svsm.c b/drivers/char/tpm/tpm_svsm.c
index b8aa7eb567de..547d4c4f7a53 100644
--- a/drivers/char/tpm/tpm_svsm.c
+++ b/drivers/char/tpm/tpm_svsm.c
@@ -25,38 +25,32 @@ struct tpm_svsm_priv {
 	void *buffer;
 };
 
-static int tpm_svsm_send(struct tpm_chip *chip, u8 *buf, size_t len,
+static int tpm_svsm_send(struct tpm_chip *chip, u8 *buf, size_t cmd_len,
 			 size_t buf_size)
 {
 	struct tpm_svsm_priv *priv = dev_get_drvdata(&chip->dev);
 	int ret;
 
-	ret = svsm_vtpm_cmd_request_fill(priv->buffer, 0, buf, len);
+	ret = svsm_vtpm_cmd_request_fill(priv->buffer, 0, buf, cmd_len);
 	if (ret)
 		return ret;
 
 	/*
 	 * The SVSM call uses the same buffer for the command and for the
-	 * response, so after this call, the buffer will contain the response
-	 * that can be used by .recv() op.
+	 * response, so after this call, the buffer will contain the response.
+	 *
+	 * Note: we have to use an internal buffer because the device in SVSM
+	 * expects the svsm_vtpm header + data to be physically contiguous.
 	 */
-	return snp_svsm_vtpm_send_command(priv->buffer);
-}
-
-static int tpm_svsm_recv(struct tpm_chip *chip, u8 *buf, size_t len)
-{
-	struct tpm_svsm_priv *priv = dev_get_drvdata(&chip->dev);
+	ret = snp_svsm_vtpm_send_command(priv->buffer);
+	if (ret)
+		return ret;
 
-	/*
-	 * The internal buffer contains the response after we send the command
-	 * to SVSM.
-	 */
-	return svsm_vtpm_cmd_response_parse(priv->buffer, buf, len);
+	return svsm_vtpm_cmd_response_parse(priv->buffer, buf, buf_size);
 }
 
 static struct tpm_class_ops tpm_chip_ops = {
 	.flags = TPM_OPS_AUTO_STARTUP,
-	.recv = tpm_svsm_recv,
 	.send = tpm_svsm_send,
 };
 
@@ -88,6 +82,7 @@ static int __init tpm_svsm_probe(struct platform_device *pdev)
 
 	dev_set_drvdata(&chip->dev, priv);
 
+	chip->flags |= TPM_CHIP_FLAG_SYNC;
 	err = tpm2_probe(chip);
 	if (err)
 		return err;
-- 
2.49.0

Re: [PATCH v2 2/4] tpm: support devices with synchronous send()

[Jarkko Sakkinen]

On Tue, Apr 08, 2025 at 10:32:06AM +0200, Stefano Garzarella wrote:
> From: Stefano Garzarella <sgarzare@redhat.com>
> 
> Some devices do not support interrupts and provide a single synchronous
> operation to send the command and receive the response on the same buffer.
> 
> Currently, these types of drivers must use an internal buffer where they
> temporarily store the response between .send() and recv() calls.
> 
> Introduce a new flag (TPM_CHIP_FLAG_SYNC) to support synchronous send().
> If that flag is set by the driver, tpm_try_transmit() will use the send()
> callback to send the command and receive the response on the same buffer
> synchronously. In that case send() return the number of bytes of the
> response on success, or -errno on failure.
> 
> Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
> Suggested-by: Jarkko Sakkinen <jarkko@kernel.org>
> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
> ---
>  include/linux/tpm.h              |  1 +
>  drivers/char/tpm/tpm-interface.c | 18 +++++++++++++++---
>  2 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 2e38edd5838c..0e9746dc9d30 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -350,6 +350,7 @@ enum tpm_chip_flags {
>  	TPM_CHIP_FLAG_SUSPENDED			= BIT(8),
>  	TPM_CHIP_FLAG_HWRNG_DISABLED		= BIT(9),
>  	TPM_CHIP_FLAG_DISABLE			= BIT(10),
> +	TPM_CHIP_FLAG_SYNC			= BIT(11),
>  };
>  
>  #define to_tpm_chip(d) container_of(d, struct tpm_chip, dev)
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index 3b6ddcdb4051..9fbe84b5a131 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -114,8 +114,17 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, void *buf, size_t bufsiz)
>  		return rc;
>  	}
>  
> -	/* A sanity check. send() should just return zero on success e.g.
> -	 * not the command length.
> +	/* Synchronous devices return the response directly during the send()
> +	 * call in the same buffer.
> +	 */

Nit:

/*
 * ...

It's wrong in the existing comment.

> +	if (chip->flags & TPM_CHIP_FLAG_SYNC) {
> +		len = rc;
> +		rc = 0;
> +		goto out_send_sync;
> +	}
> +
> +	/* A sanity check. send() of asynchronous devices should just return
> +	 * zero on success e.g. not the command length.
>  	 */
>  	if (rc > 0) {
>  		dev_warn(&chip->dev,
> @@ -151,7 +160,10 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, void *buf, size_t bufsiz)
>  	if (len < 0) {
>  		rc = len;
>  		dev_err(&chip->dev, "tpm_transmit: tpm_recv: error %d\n", rc);
> -	} else if (len < TPM_HEADER_SIZE || len != be32_to_cpu(header->length))
> +		return rc;
> +	}
> +out_send_sync:

out_sync would be sufficient

> +	if (len < TPM_HEADER_SIZE || len != be32_to_cpu(header->length))
>  		rc = -EFAULT;
>  
>  	return rc ? rc : len;
> -- 
> 2.49.0
> 

BR, Jarkko

Re: [PATCH v2 2/4] tpm: support devices with synchronous send()

[Stefano Garzarella]

On Tue, Apr 08, 2025 at 06:31:30PM +0300, Jarkko Sakkinen wrote:
>On Tue, Apr 08, 2025 at 10:32:06AM +0200, Stefano Garzarella wrote:
>> From: Stefano Garzarella <sgarzare@redhat.com>
>>
>> Some devices do not support interrupts and provide a single synchronous
>> operation to send the command and receive the response on the same buffer.
>>
>> Currently, these types of drivers must use an internal buffer where they
>> temporarily store the response between .send() and recv() calls.
>>
>> Introduce a new flag (TPM_CHIP_FLAG_SYNC) to support synchronous send().
>> If that flag is set by the driver, tpm_try_transmit() will use the send()
>> callback to send the command and receive the response on the same buffer
>> synchronously. In that case send() return the number of bytes of the
>> response on success, or -errno on failure.
>>
>> Suggested-by: Jason Gunthorpe <jgg@ziepe.ca>
>> Suggested-by: Jarkko Sakkinen <jarkko@kernel.org>
>> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
>> ---
>>  include/linux/tpm.h              |  1 +
>>  drivers/char/tpm/tpm-interface.c | 18 +++++++++++++++---
>>  2 files changed, 16 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
>> index 2e38edd5838c..0e9746dc9d30 100644
>> --- a/include/linux/tpm.h
>> +++ b/include/linux/tpm.h
>> @@ -350,6 +350,7 @@ enum tpm_chip_flags {
>>  	TPM_CHIP_FLAG_SUSPENDED			= BIT(8),
>>  	TPM_CHIP_FLAG_HWRNG_DISABLED		= BIT(9),
>>  	TPM_CHIP_FLAG_DISABLE			= BIT(10),
>> +	TPM_CHIP_FLAG_SYNC			= BIT(11),
>>  };
>>
>>  #define to_tpm_chip(d) container_of(d, struct tpm_chip, dev)
>> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
>> index 3b6ddcdb4051..9fbe84b5a131 100644
>> --- a/drivers/char/tpm/tpm-interface.c
>> +++ b/drivers/char/tpm/tpm-interface.c
>> @@ -114,8 +114,17 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, void *buf, size_t bufsiz)
>>  		return rc;
>>  	}
>>
>> -	/* A sanity check. send() should just return zero on success e.g.
>> -	 * not the command length.
>> +	/* Synchronous devices return the response directly during the send()
>> +	 * call in the same buffer.
>> +	 */
>
>Nit:
>
>/*
> * ...
>
>It's wrong in the existing comment.

Yep, I'll fix.

>
>> +	if (chip->flags & TPM_CHIP_FLAG_SYNC) {
>> +		len = rc;
>> +		rc = 0;
>> +		goto out_send_sync;
>> +	}
>> +
>> +	/* A sanity check. send() of asynchronous devices should just return

And I'll fix also this of course.

>> +	 * zero on success e.g. not the command length.
>>  	 */
>>  	if (rc > 0) {
>>  		dev_warn(&chip->dev,
>> @@ -151,7 +160,10 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip, void *buf, size_t bufsiz)
>>  	if (len < 0) {
>>  		rc = len;
>>  		dev_err(&chip->dev, "tpm_transmit: tpm_recv: error %d\n", rc);
>> -	} else if (len < TPM_HEADER_SIZE || len != be32_to_cpu(header->length))
>> +		return rc;
>> +	}
>> +out_send_sync:
>
>out_sync would be sufficient

sure, I'll fix in v3.

Thanks,
Stefano