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This driver does not support interrupts, and receiving the response is synchronous with sending the command. Enable synchronous send() with TPM_CHIP_FLAG_SYNC, which implies that ->send() already fills the provided buffer with a response, and ->recv() is not implemented. 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> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
122 lines
3.0 KiB
C
122 lines
3.0 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2025 Red Hat, Inc. All Rights Reserved.
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*
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* Driver for the vTPM defined by the AMD SVSM spec [1].
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*
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* The specification defines a protocol that a SEV-SNP guest OS can use to
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* discover and talk to a vTPM emulated by the Secure VM Service Module (SVSM)
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* in the guest context, but at a more privileged level (usually VMPL0).
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*
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* [1] "Secure VM Service Module for SEV-SNP Guests"
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* Publication # 58019 Revision: 1.00
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/platform_device.h>
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#include <linux/tpm_svsm.h>
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#include <asm/sev.h>
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#include "tpm.h"
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struct tpm_svsm_priv {
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void *buffer;
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};
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static int tpm_svsm_send(struct tpm_chip *chip, u8 *buf, size_t bufsiz,
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size_t cmd_len)
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{
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struct tpm_svsm_priv *priv = dev_get_drvdata(&chip->dev);
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int ret;
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ret = svsm_vtpm_cmd_request_fill(priv->buffer, 0, buf, cmd_len);
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if (ret)
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return ret;
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/*
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* The SVSM call uses the same buffer for the command and for the
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* response, so after this call, the buffer will contain the response.
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*
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* Note: we have to use an internal buffer because the device in SVSM
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* expects the svsm_vtpm header + data to be physically contiguous.
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*/
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ret = snp_svsm_vtpm_send_command(priv->buffer);
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if (ret)
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return ret;
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return svsm_vtpm_cmd_response_parse(priv->buffer, buf, bufsiz);
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}
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static struct tpm_class_ops tpm_chip_ops = {
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.flags = TPM_OPS_AUTO_STARTUP,
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.send = tpm_svsm_send,
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};
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static int __init tpm_svsm_probe(struct platform_device *pdev)
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{
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struct device *dev = &pdev->dev;
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struct tpm_svsm_priv *priv;
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struct tpm_chip *chip;
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int err;
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priv = devm_kmalloc(dev, sizeof(*priv), GFP_KERNEL);
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if (!priv)
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return -ENOMEM;
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/*
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* The maximum buffer supported is one page (see SVSM_VTPM_MAX_BUFFER
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* in tpm_svsm.h).
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*/
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priv->buffer = (void *)devm_get_free_pages(dev, GFP_KERNEL, 0);
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if (!priv->buffer)
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return -ENOMEM;
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chip = tpmm_chip_alloc(dev, &tpm_chip_ops);
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if (IS_ERR(chip))
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return PTR_ERR(chip);
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dev_set_drvdata(&chip->dev, priv);
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chip->flags |= TPM_CHIP_FLAG_SYNC;
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err = tpm2_probe(chip);
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if (err)
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return err;
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err = tpm_chip_register(chip);
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if (err)
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return err;
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dev_info(dev, "SNP SVSM vTPM %s device\n",
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(chip->flags & TPM_CHIP_FLAG_TPM2) ? "2.0" : "1.2");
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return 0;
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}
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static void __exit tpm_svsm_remove(struct platform_device *pdev)
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{
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struct tpm_chip *chip = platform_get_drvdata(pdev);
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tpm_chip_unregister(chip);
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}
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/*
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* tpm_svsm_remove() lives in .exit.text. For drivers registered via
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* module_platform_driver_probe() this is ok because they cannot get unbound
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* at runtime. So mark the driver struct with __refdata to prevent modpost
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* triggering a section mismatch warning.
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*/
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static struct platform_driver tpm_svsm_driver __refdata = {
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.remove = __exit_p(tpm_svsm_remove),
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.driver = {
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.name = "tpm-svsm",
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},
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};
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module_platform_driver_probe(tpm_svsm_driver, tpm_svsm_probe);
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MODULE_DESCRIPTION("SNP SVSM vTPM Driver");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("platform:tpm-svsm");
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