Re: [PATCH v3 4/4] x86/sev: register tpm-svsm platform device

[Tom Lendacky]

On 3/11/25 04:42, Stefano Garzarella wrote:
> SNP platform can provide a vTPM device emulated by SVSM.
> 
> The "tpm-svsm" device can be handled by the platform driver added
> by the previous commit in drivers/char/tpm/tpm_svsm.c
> 
> The driver will call snp_svsm_vtpm_probe() to check if SVSM is
> present and if it's support the vTPM protocol.
> 
> Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> ---
>  arch/x86/coco/sev/core.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
> index 2166bdff88b7..a2383457889e 100644
> --- a/arch/x86/coco/sev/core.c
> +++ b/arch/x86/coco/sev/core.c
> @@ -2664,6 +2664,11 @@ static struct platform_device sev_guest_device = {
>  	.id		= -1,
>  };
>  
> +static struct platform_device tpm_svsm_device = {
> +	.name		= "tpm-svsm",
> +	.id		= -1,
> +};
> +
>  static int __init snp_init_platform_device(void)
>  {
>  	if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
> @@ -2672,6 +2677,9 @@ static int __init snp_init_platform_device(void)
>  	if (platform_device_register(&sev_guest_device))
>  		return -ENODEV;
>  
> +	if (platform_device_register(&tpm_svsm_device))
> +		return -ENODEV;
> +

You could avoid registering the device if an SVSM isn't present. Not sure
if that is desirable or not.

Thanks,
Tom

>  	pr_info("SNP guest platform device initialized.\n");
>  	return 0;
>  }