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@xxxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> Co-developed-by: Claudio Carvalho <cclaudio@xxxxxxxxxxxxx>
> Signed-off-by: Claudio Carvalho <cclaudio@xxxxxxxxxxxxx>
> Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
One minor nit below, otherwise:
Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> ---
> 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,
