linux-kernel - Re: [RFC PATCH 3/4] crypto: ccp - Add an API to return the supported SEV-SNP policy bits

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Message-ID: <aMHP5EO-ucJGdHXz@google.com>
Date: Wed, 10 Sep 2025 12:22:12 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, x86@...nel.org, 
	linux-crypto@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	Ingo Molnar <mingo@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Michael Roth <michael.roth@....com>, Ashish Kalra <ashish.kalra@....com>, 
	Herbert Xu <herbert@...dor.apana.org.au>, David Miller <davem@...emloft.net>
Subject: Re: [RFC PATCH 3/4] crypto: ccp - Add an API to return the supported
 SEV-SNP policy bits

On Fri, Aug 22, 2025, Tom Lendacky wrote:
> @@ -1014,6 +1031,7 @@ void *snp_alloc_firmware_page(gfp_t mask);
>  void snp_free_firmware_page(void *addr);
>  void sev_platform_shutdown(void);
>  bool sev_is_snp_ciphertext_hiding_supported(void);
> +u64 sev_get_snp_policy_bits(void);
>  
>  #else	/* !CONFIG_CRYPTO_DEV_SP_PSP */
>  
> @@ -1052,6 +1070,8 @@ static inline void sev_platform_shutdown(void) { }
>  
>  static inline bool sev_is_snp_ciphertext_hiding_supported(void) { return false; }
>  
> +static inline u64 sev_get_snp_policy_bits(void) { return 0; }

I don't think you need a stub (the ciphertext hiding one should have been omitted
too).  arch/x86/kvm/svm/sev.c depends on CONFIG_KVM_AMD_SEV=y, which in turn
depends on CRYPTO_DEV_SP_PSP=y, so nothing will ever actually need the stub.  I
bet the same holds true for the majority of these stubs.