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Message-ID: <20250324104653.138663-2-sgarzare@redhat.com>
Date: Mon, 24 Mar 2025 11:46:46 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Jarkko Sakkinen <jarkko@...nel.org>
Cc: Joerg Roedel <jroedel@...e.de>,
Ingo Molnar <mingo@...hat.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Peter Huewe <peterhuewe@....de>,
Tom Lendacky <thomas.lendacky@....com>,
Thomas Gleixner <tglx@...utronix.de>,
x86@...nel.org,
James Bottomley <James.Bottomley@...senPartnership.com>,
linux-kernel@...r.kernel.org,
Borislav Petkov <bp@...en8.de>,
Jason Gunthorpe <jgg@...pe.ca>,
"H. Peter Anvin" <hpa@...or.com>,
linux-coco@...ts.linux.dev,
Claudio Carvalho <cclaudio@...ux.ibm.com>,
Dov Murik <dovmurik@...ux.ibm.com>,
Dionna Glaze <dionnaglaze@...gle.com>,
linux-integrity@...r.kernel.org,
Stefano Garzarella <sgarzare@...hat.com>
Subject: [PATCH v4 1/4] x86/sev: add SVSM vTPM probe/send_command functions
From: Stefano Garzarella <sgarzare@...hat.com>
Add two new functions to probe and send commands to the SVSM vTPM.
They leverage the two calls defined by the AMD SVSM specification [1]
for the vTPM protocol: SVSM_VTPM_QUERY and SVSM_VTPM_CMD.
Expose these functions to be used by other modules such as a tpm
driver.
[1] "Secure VM Service Module for SEV-SNP Guests"
Publication # 58019 Revision: 1.00
Co-developed-by: James Bottomley <James.Bottomley@...senPartnership.com>
Signed-off-by: James Bottomley <James.Bottomley@...senPartnership.com>
Co-developed-by: Claudio Carvalho <cclaudio@...ux.ibm.com>
Signed-off-by: Claudio Carvalho <cclaudio@...ux.ibm.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
---
v4:
- added Tom's R-b
- added functions documentation [Jarkko]
- simplified TPM_SEND_COMMAND check [Tom/Jarkko]
v3:
- removed link to the spec because those URLs are unstable [Borislav]
- squashed "x86/sev: add SVSM call macros for the vTPM protocol" patch
in this one [Borislav]
- slimmed down snp_svsm_vtpm_probe() [Borislav]
- removed features check and any print related [Tom]
---
arch/x86/include/asm/sev.h | 7 +++++
arch/x86/coco/sev/core.c | 59 ++++++++++++++++++++++++++++++++++++++
2 files changed, 66 insertions(+)
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index ba7999f66abe..09471d058ce5 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -384,6 +384,10 @@ struct svsm_call {
#define SVSM_ATTEST_SERVICES 0
#define SVSM_ATTEST_SINGLE_SERVICE 1
+#define SVSM_VTPM_CALL(x) ((2ULL << 32) | (x))
+#define SVSM_VTPM_QUERY 0
+#define SVSM_VTPM_CMD 1
+
#ifdef CONFIG_AMD_MEM_ENCRYPT
extern u8 snp_vmpl;
@@ -481,6 +485,9 @@ void snp_msg_free(struct snp_msg_desc *mdesc);
int snp_send_guest_request(struct snp_msg_desc *mdesc, struct snp_guest_req *req,
struct snp_guest_request_ioctl *rio);
+bool snp_svsm_vtpm_probe(void);
+int snp_svsm_vtpm_send_command(u8 *buffer);
+
void __init snp_secure_tsc_prepare(void);
void __init snp_secure_tsc_init(void);
diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 96c7bc698e6b..034aab7e76d2 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -2628,6 +2628,65 @@ static int snp_issue_guest_request(struct snp_guest_req *req, struct snp_req_dat
return ret;
}
+/**
+ * snp_svsm_vtpm_probe() - Probe if SVSM provides a vTPM device
+ *
+ * This function checks that there is SVSM and that it supports at least
+ * TPM_SEND_COMMAND which is the only request we use so far.
+ *
+ * Return: true if the platform provides a vTPM SVSM device, false otherwise.
+ */
+bool snp_svsm_vtpm_probe(void)
+{
+ struct svsm_call call = {};
+
+ /* The vTPM device is available only if a SVSM is present */
+ if (!snp_vmpl)
+ return false;
+
+ call.caa = svsm_get_caa();
+ call.rax = SVSM_VTPM_CALL(SVSM_VTPM_QUERY);
+
+ if (svsm_perform_call_protocol(&call))
+ return false;
+
+ /* Check platform commands contains TPM_SEND_COMMAND - platform command 8 */
+ return call.rcx_out & BIT_ULL(8);
+}
+EXPORT_SYMBOL_GPL(snp_svsm_vtpm_probe);
+
+/**
+ * snp_svsm_vtpm_send_command() - execute a vTPM operation on SVSM
+ * @buffer: A buffer used to both send the command and receive the response.
+ *
+ * This function executes a SVSM_VTPM_CMD call as defined by
+ * "Secure VM Service Module for SEV-SNP Guests" Publication # 58019 Revision: 1.00
+ *
+ * All command request/response buffers have a common structure as specified by
+ * the following table:
+ * Byte Size In/Out Description
+ * Offset (Bytes)
+ * 0x000 4 In Platform command
+ * Out Platform command response size
+ *
+ * Each command can build upon this common request/response structure to create
+ * a structure specific to the command.
+ * See include/linux/tpm_svsm.h for more details.
+ *
+ * Return: 0 on success, -errno on failure
+ */
+int snp_svsm_vtpm_send_command(u8 *buffer)
+{
+ struct svsm_call call = {};
+
+ call.caa = svsm_get_caa();
+ call.rax = SVSM_VTPM_CALL(SVSM_VTPM_CMD);
+ call.rcx = __pa(buffer);
+
+ return svsm_perform_call_protocol(&call);
+}
+EXPORT_SYMBOL_GPL(snp_svsm_vtpm_send_command);
+
static struct platform_device sev_guest_device = {
.name = "sev-guest",
.id = -1,
--
2.49.0
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