| Message ID | 20250324104653.138663-3-sgarzare@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Enlightened vTPM support for SVSM on SEV-SNP | expand |
On Mon, Mar 24, 2025 at 11:46:47AM +0100, Stefano Garzarella wrote: > From: Stefano Garzarella <sgarzare@redhat.com> > > Helpers for the SVSM_VTPM_CMD calls used by the vTPM protocol defined by > the AMD SVSM spec [1]. > > The vTPM protocol follows the Official TPM 2.0 Reference Implementation > (originally by Microsoft, now part of the TCG) simulator protocol. > > [1] "Secure VM Service Module for SEV-SNP Guests" > Publication # 58019 Revision: 1.00 > > Co-developed-by: James Bottomley <James.Bottomley@HansenPartnership.com> > Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com> > Co-developed-by: Claudio Carvalho <cclaudio@linux.ibm.com> > Signed-off-by: Claudio Carvalho <cclaudio@linux.ibm.com> > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> > --- > v4: > - used svsm_vtpm_ prefix consistently [Jarkko] > - removed __packed where not needed [Jarkko] > - expanded headers to avoid obfuscation [Jarkko] > - used `buf` instead of `inbuf`/`outbuf` [Jarkko] > - added more documentation quoting the specification > - removed TPM_* macros since we only use TPM_SEND_COMMAND in one place > and don't want dependencies on external headers, but put the value > directly as specified in the AMD SVSM specification > - header renamed in tpm_svsm.h so it will fall under TPM DEVICE DRIVER > section [Borislav, Jarkko] > v3: > - renamed header and prefix to make clear it's related to the SVSM vTPM > protocol > - renamed fill/parse functions [Tom] > - removed link to the spec because those URLs are unstable [Borislav] > --- > include/linux/tpm_svsm.h | 149 +++++++++++++++++++++++++++++++++++++++ > 1 file changed, 149 insertions(+) > create mode 100644 include/linux/tpm_svsm.h > > diff --git a/include/linux/tpm_svsm.h b/include/linux/tpm_svsm.h > new file mode 100644 > index 000000000000..38e341f9761a > --- /dev/null > +++ b/include/linux/tpm_svsm.h > @@ -0,0 +1,149 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Copyright (C) 2023 James.Bottomley@HansenPartnership.com > + * Copyright (C) 2025 Red Hat, Inc. All Rights Reserved. > + * > + * Helpers for the SVSM_VTPM_CMD calls used by the vTPM protocol defined by the > + * AMD SVSM spec [1]. > + * > + * The vTPM protocol follows the Official TPM 2.0 Reference Implementation > + * (originally by Microsoft, now part of the TCG) simulator protocol. > + * > + * [1] "Secure VM Service Module for SEV-SNP Guests" > + * Publication # 58019 Revision: 1.00 > + */ > +#ifndef _TPM_SVSM_H_ > +#define _TPM_SVSM_H_ > + > +#include <linux/errno.h> > +#include <linux/string.h> > +#include <linux/types.h> > + > +#define SVSM_VTPM_MAX_BUFFER 4096 /* max req/resp buffer size */ > + > +/** > + * struct svsm_vtpm_request - Generic request for single word command > + * @cmd: The command to send > + * > + * Defined by AMD SVSM spec [1] in section "8.2 SVSM_VTPM_CMD Call" - > + * Table 15: vTPM Common Request/Response Structure > + * Byte Size In/Out Description > + * Offset (Bytes) > + * 0x000 4 In Platform command > + * Out Platform command response size > + */ > +struct svsm_vtpm_request { > + u32 cmd; > +}; > + > +/** > + * struct svsm_vtpm_response - Generic response > + * @size: The response size (zero if nothing follows) > + * > + * Defined by AMD SVSM spec [1] in section "8.2 SVSM_VTPM_CMD Call" - > + * Table 15: vTPM Common Request/Response Structure > + * Byte Size In/Out Description > + * Offset (Bytes) > + * 0x000 4 In Platform command > + * Out Platform command response size > + * > + * Note: most TCG Simulator commands simply return zero here with no indication > + * of success or failure. > + */ > +struct svsm_vtpm_response { > + u32 size; > +}; > + > +/** > + * struct svsm_vtpm_cmd_request - Structure for a TPM_SEND_COMMAND request > + * @cmd: The command to send (must be TPM_SEND_COMMAND) > + * @locality: The locality > + * @buf_size: The size of the input buffer following > + * @buf: A buffer of size buf_size > + * > + * Defined by AMD SVSM spec [1] in section "8.2 SVSM_VTPM_CMD Call" - > + * Table 16: TPM_SEND_COMMAND Request Structure > + * Byte Size Meaning > + * Offset (Bytes) > + * 0x000 4 Platform command (8) > + * 0x004 1 Locality (must-be-0) > + * 0x005 4 TPM Command size (in bytes) > + * 0x009 Variable TPM Command > + * > + * Note: the TCG Simulator expects @buf_size to be equal to the size of the > + * specific TPM command, otherwise an TPM_RC_COMMAND_SIZE error is returned. > + */ > +struct svsm_vtpm_cmd_request { > + u32 cmd; > + u8 locality; > + u32 buf_size; > + u8 buf[]; > +} __packed; > + > +/** > + * struct svsm_vtpm_cmd_response - Structure for a TPM_SEND_COMMAND response > + * @buf_size: The size of the output buffer following > + * @buf: A buffer of size buf_size > + * > + * Defined by AMD SVSM spec [1] in section "8.2 SVSM_VTPM_CMD Call" - > + * Table 17: TPM_SEND_COMMAND Response Structure > + * Byte Size Meaning > + * Offset (Bytes) > + * 0x000 4 Response size (in bytes) > + * 0x004 Variable Response > + */ > +struct svsm_vtpm_cmd_response { > + u32 buf_size; > + u8 buf[]; > +}; > + > +/** > + * svsm_vtpm_cmd_request_fill() - Fill a TPM_SEND_COMMAND request to be sent to SVSM > + * @req: The struct svsm_vtpm_cmd_request to fill > + * @locality: The locality > + * @buf: The buffer from where to copy the payload of the command > + * @len: The size of the buffer > + * > + * Return: 0 on success, negative error code on failure. > + */ > +static inline int > +svsm_vtpm_cmd_request_fill(struct svsm_vtpm_cmd_request *req, u8 locality, > + const u8 *buf, size_t len) > +{ > + if (len > SVSM_VTPM_MAX_BUFFER - sizeof(*req)) > + return -EINVAL; > + > + req->cmd = 8; /* TPM_SEND_COMMAND */ > + req->locality = locality; > + req->buf_size = len; > + > + memcpy(req->buf, buf, len); > + > + return 0; > +} > + > +/** > + * svsm_vtpm_cmd_response_parse() - Parse a TPM_SEND_COMMAND response received from SVSM > + * @resp: The struct svsm_vtpm_cmd_response to parse > + * @buf: The buffer where to copy the response > + * @len: The size of the buffer > + * > + * Return: buffer size filled with the response on success, negative error > + * code on failure. > + */ > +static inline int > +svsm_vtpm_cmd_response_parse(const struct svsm_vtpm_cmd_response *resp, u8 *buf, > + size_t len) > +{ > + if (len < resp->buf_size) > + return -E2BIG; > + > + if (resp->buf_size > SVSM_VTPM_MAX_BUFFER - sizeof(*resp)) > + return -EINVAL; // Invalid response from the platform TPM > + > + memcpy(buf, resp->buf, resp->buf_size); > + > + return resp->buf_size; > +} > + > +#endif /* _TPM_SVSM_H_ */ > -- > 2.49.0 > Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> BR, Jarkko
diff --git a/include/linux/tpm_svsm.h b/include/linux/tpm_svsm.h new file mode 100644 index 000000000000..38e341f9761a --- /dev/null +++ b/include/linux/tpm_svsm.h @@ -0,0 +1,149 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (C) 2023 James.Bottomley@HansenPartnership.com + * Copyright (C) 2025 Red Hat, Inc. All Rights Reserved. + * + * Helpers for the SVSM_VTPM_CMD calls used by the vTPM protocol defined by the + * AMD SVSM spec [1]. + * + * The vTPM protocol follows the Official TPM 2.0 Reference Implementation + * (originally by Microsoft, now part of the TCG) simulator protocol. + * + * [1] "Secure VM Service Module for SEV-SNP Guests" + * Publication # 58019 Revision: 1.00 + */ +#ifndef _TPM_SVSM_H_ +#define _TPM_SVSM_H_ + +#include <linux/errno.h> +#include <linux/string.h> +#include <linux/types.h> + +#define SVSM_VTPM_MAX_BUFFER 4096 /* max req/resp buffer size */ + +/** + * struct svsm_vtpm_request - Generic request for single word command + * @cmd: The command to send + * + * Defined by AMD SVSM spec [1] in section "8.2 SVSM_VTPM_CMD Call" - + * Table 15: vTPM Common Request/Response Structure + * Byte Size In/Out Description + * Offset (Bytes) + * 0x000 4 In Platform command + * Out Platform command response size + */ +struct svsm_vtpm_request { + u32 cmd; +}; + +/** + * struct svsm_vtpm_response - Generic response + * @size: The response size (zero if nothing follows) + * + * Defined by AMD SVSM spec [1] in section "8.2 SVSM_VTPM_CMD Call" - + * Table 15: vTPM Common Request/Response Structure + * Byte Size In/Out Description + * Offset (Bytes) + * 0x000 4 In Platform command + * Out Platform command response size + * + * Note: most TCG Simulator commands simply return zero here with no indication + * of success or failure. + */ +struct svsm_vtpm_response { + u32 size; +}; + +/** + * struct svsm_vtpm_cmd_request - Structure for a TPM_SEND_COMMAND request + * @cmd: The command to send (must be TPM_SEND_COMMAND) + * @locality: The locality + * @buf_size: The size of the input buffer following + * @buf: A buffer of size buf_size + * + * Defined by AMD SVSM spec [1] in section "8.2 SVSM_VTPM_CMD Call" - + * Table 16: TPM_SEND_COMMAND Request Structure + * Byte Size Meaning + * Offset (Bytes) + * 0x000 4 Platform command (8) + * 0x004 1 Locality (must-be-0) + * 0x005 4 TPM Command size (in bytes) + * 0x009 Variable TPM Command + * + * Note: the TCG Simulator expects @buf_size to be equal to the size of the + * specific TPM command, otherwise an TPM_RC_COMMAND_SIZE error is returned. + */ +struct svsm_vtpm_cmd_request { + u32 cmd; + u8 locality; + u32 buf_size; + u8 buf[]; +} __packed; + +/** + * struct svsm_vtpm_cmd_response - Structure for a TPM_SEND_COMMAND response + * @buf_size: The size of the output buffer following + * @buf: A buffer of size buf_size + * + * Defined by AMD SVSM spec [1] in section "8.2 SVSM_VTPM_CMD Call" - + * Table 17: TPM_SEND_COMMAND Response Structure + * Byte Size Meaning + * Offset (Bytes) + * 0x000 4 Response size (in bytes) + * 0x004 Variable Response + */ +struct svsm_vtpm_cmd_response { + u32 buf_size; + u8 buf[]; +}; + +/** + * svsm_vtpm_cmd_request_fill() - Fill a TPM_SEND_COMMAND request to be sent to SVSM + * @req: The struct svsm_vtpm_cmd_request to fill + * @locality: The locality + * @buf: The buffer from where to copy the payload of the command + * @len: The size of the buffer + * + * Return: 0 on success, negative error code on failure. + */ +static inline int +svsm_vtpm_cmd_request_fill(struct svsm_vtpm_cmd_request *req, u8 locality, + const u8 *buf, size_t len) +{ + if (len > SVSM_VTPM_MAX_BUFFER - sizeof(*req)) + return -EINVAL; + + req->cmd = 8; /* TPM_SEND_COMMAND */ + req->locality = locality; + req->buf_size = len; + + memcpy(req->buf, buf, len); + + return 0; +} + +/** + * svsm_vtpm_cmd_response_parse() - Parse a TPM_SEND_COMMAND response received from SVSM + * @resp: The struct svsm_vtpm_cmd_response to parse + * @buf: The buffer where to copy the response + * @len: The size of the buffer + * + * Return: buffer size filled with the response on success, negative error + * code on failure. + */ +static inline int +svsm_vtpm_cmd_response_parse(const struct svsm_vtpm_cmd_response *resp, u8 *buf, + size_t len) +{ + if (len < resp->buf_size) + return -E2BIG; + + if (resp->buf_size > SVSM_VTPM_MAX_BUFFER - sizeof(*resp)) + return -EINVAL; // Invalid response from the platform TPM + + memcpy(buf, resp->buf, resp->buf_size); + + return resp->buf_size; +} + +#endif /* _TPM_SVSM_H_ */