From: Mike Larkin <mlarkin@nested.page>
Subject: Re: SEV-SNP: Log SEV-SNP guestmode
To: tech@openbsd.org
Date: Wed, 29 Jul 2026 09:39:46 -0700

On Wed, Jul 29, 2026 at 03:51:58PM +0200, hshoexer wrote:
> Hi,
>
> this diff is the first of series of diffs, that enable SEV-SNP guest
> support for OpenBSD.
>
> NB:  The definition SEV_STAT_SNP_ACTIVE is straight from the AMD
> documentation.  The use of "active" instead of "enabled" -- as with
> the other definitions -- feels inconsistent.  However, "SNP enabled"
> in the context of SNP means the host system is able to run VMs using
> SNP.  And "SNP active" means, the guest is actually using SNP.  And
> not just e.g. SEV-ES.
>
> ok?
>

ok mlarkin

> ---------------------------------------------
> diff --git a/sys/arch/amd64/amd64/identcpu.c b/sys/arch/amd64/amd64/identcpu.c
> index 51e8344d573..6c56d584eb0 100644
> --- a/sys/arch/amd64/amd64/identcpu.c
> +++ b/sys/arch/amd64/amd64/identcpu.c
> @@ -712,10 +712,13 @@ identifycpu(struct cpu_info *ci)
>  		    CPUID_AMDSEV_EDX_BITS);
>  		amd64_pos_cbit = (ci->ci_feature_amdsev_ebx & 0x3f);
>  		amd64_min_noes_asid = ci->ci_feature_amdsev_edx;
> -		if (cpu_sev_guestmode && CPU_IS_PRIMARY(ci))
> +		if (cpu_sev_guestmode && CPU_IS_PRIMARY(ci)) {
>  			printf("\n%s: SEV%s guest mode", ci->ci_dev->dv_xname,
> -			    ISSET(cpu_sev_guestmode, SEV_STAT_ES_ENABLED) ?
> -			    "-ES" : "");
> +			    ISSET(cpu_sev_guestmode, SEV_STAT_SNP_ACTIVE) ?
> +			    "-SNP" :
> +			    (ISSET(cpu_sev_guestmode, SEV_STAT_ES_ENABLED) ?
> +			    "-ES" : ""));
> +		}
>  	}
>
>  	printf("\n");
> diff --git a/sys/arch/amd64/include/specialreg.h b/sys/arch/amd64/include/specialreg.h
> index 5240f19351a..299c8fbc6c4 100644
> --- a/sys/arch/amd64/include/specialreg.h
> +++ b/sys/arch/amd64/include/specialreg.h
> @@ -737,6 +737,7 @@
>  #define MSR_SEV_STATUS	0xc0010131
>  #define		SEV_STAT_ENABLED	0x00000001
>  #define		SEV_STAT_ES_ENABLED	0x00000002
> +#define		SEV_STAT_SNP_ACTIVE	0x00000004
>
>  #define	MSR_LS_CFG	0xc0011020
>  #define		LS_CFG_DIS_LS2_SQUISH	0x02000000
>