linux-kernel - [PATCH v3 4/4] tpm/tpm_svsm: support TPM_CHIP_FLAG

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Message-ID: <20250414145653.239081-5-sgarzare@redhat.com>
Date: Mon, 14 Apr 2025 16:56:53 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Jarkko Sakkinen <jarkko@...nel.org>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	Peter Huewe <peterhuewe@....de>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	Jens Wiklander <jens.wiklander@...aro.org>,
	Claudiu Beznea <claudiu.beznea@...on.dev>,
	Naveen N Rao <naveen@...nel.org>,
	Nicholas Piggin <npiggin@...il.com>,
	linuxppc-dev@...ts.ozlabs.org,
	Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	linux-integrity@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Sumit Garg <sumit.garg@...nel.org>,
	linux-kernel@...r.kernel.org,
	Jason Gunthorpe <jgg@...pe.ca>,
	Stefano Garzarella <sgarzare@...hat.com>
Subject: [PATCH v3 4/4] tpm/tpm_svsm: support TPM_CHIP_FLAG_SYNC

From: Stefano Garzarella <sgarzare@...hat.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@...hat.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 d3ca5615b6f7..db1983072345 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,
 };
 
@@ -85,6 +79,7 @@ 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