linux-kernel - Re: [PATCH v5 4/4] x86/sev: register tpm-svsm platform device

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Message-ID: <1c985127-626c-cd09-4dfc-c5607185de85@amd.com>
Date: Mon, 31 Mar 2025 11:10:26 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Stefano Garzarella <sgarzare@...hat.com>,
 Jarkko Sakkinen <jarkko@...nel.org>
Cc: linux-kernel@...r.kernel.org, Jason Gunthorpe <jgg@...pe.ca>,
 James Bottomley <James.Bottomley@...senPartnership.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>, Borislav Petkov <bp@...en8.de>,
 linux-integrity@...r.kernel.org, Peter Huewe <peterhuewe@....de>,
 Ingo Molnar <mingo@...hat.com>, linux-coco@...ts.linux.dev,
 Dov Murik <dovmurik@...ux.ibm.com>, Thomas Gleixner <tglx@...utronix.de>,
 Joerg Roedel <jroedel@...e.de>, x86@...nel.org,
 Dionna Glaze <dionnaglaze@...gle.com>,
 Claudio Carvalho <cclaudio@...ux.ibm.com>, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v5 4/4] x86/sev: register tpm-svsm platform device

On 3/31/25 05:38, Stefano Garzarella wrote:
> From: Stefano Garzarella <sgarzare@...hat.com>
> 
> 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
> 
> Register the device unconditionally. The support check (e.g. SVSM, cmd)
> is in snp_svsm_vtpm_probe(), keeping all logic in one place.
> This function is called during the driver's probe along with other
> setup tasks like memory allocation.
> 
> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>

> ---
> v4:
> - explained better why we register it anyway in the commit message
> ---
>  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 efb43c9d3d30..acbd9bc526b1 100644
> --- a/arch/x86/coco/sev/core.c
> +++ b/arch/x86/coco/sev/core.c
> @@ -2689,6 +2689,11 @@ 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))
> @@ -2697,6 +2702,9 @@ 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;
> +
>  	pr_info("SNP guest platform device initialized.\n");
>  	return 0;
>  }