Re: [PATCH v3 1/4] x86/sev: add SVSM vTPM probe/send_command functions
From: Tom Lendacky <thomas.lendacky@amd.com>
Date: 2025-03-14 15:27:14
Also in:
linux-integrity, lkml
On 3/11/25 04:42, Stefano Garzarella wrote:
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@HansenPartnership.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Co-developed-by: Claudio Carvalho <redacted>
Signed-off-by: Claudio Carvalho <redacted>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>One minor nit below, otherwise: Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
quoted hunk ↗ jump to hunk
--- 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 | 31 +++++++++++++++++++++++++++++++ 2 files changed, 38 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..2166bdff88b7 100644 --- a/arch/x86/coco/sev/core.c +++ b/arch/x86/coco/sev/core.c@@ -2628,6 +2628,37 @@ static int snp_issue_guest_request(struct snp_guest_req *req, struct snp_req_dat return ret; } +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)) == BIT_ULL(8);
It's a bool function, so this could simplified to just: return call.rcx_out & BIT_ULL(8); Thanks, Tom
+}
+EXPORT_SYMBOL_GPL(snp_svsm_vtpm_probe);
+
+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,