linux-kernel - Re: [PATCH v13 09/26] KVM: SEV: Add KVM_SEV_SNP_LAUNCH

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Date: Fri, 19 Apr 2024 13:52:24 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Michael Roth <michael.roth@....com>
Cc: kvm@...r.kernel.org, linux-coco@...ts.linux.dev, linux-mm@...ck.org, 
	linux-crypto@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org, 
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	thomas.lendacky@....com, hpa@...or.com, ardb@...nel.org, seanjc@...gle.com, 
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	sathyanarayanan.kuppuswamy@...ux.intel.com, alpergun@...gle.com, 
	jarkko@...nel.org, ashish.kalra@....com, nikunj.dadhania@....com, 
	pankaj.gupta@....com, liam.merwick@...cle.com, 
	Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v13 09/26] KVM: SEV: Add KVM_SEV_SNP_LAUNCH_START command

On Thu, Apr 18, 2024 at 9:42 PM Michael Roth <michael.roth@....com> wrote:
> +/* As defined by SEV-SNP Firmware ABI, under "Guest Policy". */
> +#define SNP_POLICY_MASK_API_MAJOR      GENMASK_ULL(15, 8)
> +#define SNP_POLICY_MASK_API_MINOR      GENMASK_ULL(7, 0)
> +
> +#define SNP_POLICY_MASK_VALID          (SNP_POLICY_MASK_SMT            | \
> +                                        SNP_POLICY_MASK_RSVD_MBO       | \
> +                                        SNP_POLICY_MASK_DEBUG          | \
> +                                        SNP_POLICY_MASK_SINGLE_SOCKET  | \
> +                                        SNP_POLICY_MASK_API_MAJOR      | \
> +                                        SNP_POLICY_MASK_API_MINOR)
> +
> +/* KVM's SNP support is compatible with 1.51 of the SEV-SNP Firmware ABI */
> +#define SNP_POLICY_API_MAJOR           1
> +#define SNP_POLICY_API_MINOR           51

> +static inline bool sev_version_greater_or_equal(u8 major, u8 minor)
> +{
> +       if (major < SNP_POLICY_API_MAJOR)
> +               return true;

Should it perhaps refuse version 0.x? With something like a

#define SNP_POLICY_API_MAJOR_MIN    1

to make it a bit more future proof (and testable).

> +       major = (params.policy & SNP_POLICY_MASK_API_MAJOR);

This should be >> 8. Do the QEMU patches not set the API version? :)

Paolo