linux-kernel - Re: [PATCH v3 1/4] x86/sev: add SVSM vTPM probe/send

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <d7e5a1d2-5fcc-bf7f-a67d-7871a1627c98@amd.com>
Date: Fri, 14 Mar 2025 10:27:07 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Stefano Garzarella <sgarzare@...hat.com>,
 Jarkko Sakkinen <jarkko@...nel.org>
Cc: Peter Huewe <peterhuewe@....de>, Jason Gunthorpe <jgg@...pe.ca>,
 x86@...nel.org, linux-kernel@...r.kernel.org, Borislav Petkov
 <bp@...en8.de>, linux-integrity@...r.kernel.org,
 Dov Murik <dovmurik@...ux.ibm.com>, Dionna Glaze <dionnaglaze@...gle.com>,
 linux-coco@...ts.linux.dev,
 James Bottomley <James.Bottomley@...senPartnership.com>,
 Claudio Carvalho <cclaudio@...ux.ibm.com>, Ingo Molnar <mingo@...hat.com>,
 "H. Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH v3 1/4] x86/sev: add SVSM vTPM probe/send_command
 functions

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@...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>
> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>

One minor nit below, otherwise:

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

> ---
> 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,