linux-kernel - Re: [PATCH v6 7/8] KVM: SVM: Add support to initialize SEV/SNP functionality in KVM

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Message-ID: <a2b711b5-e0d3-4abf-9a21-0553e69788f9@amd.com>
Date: Wed, 12 Mar 2025 08:34:03 -0500
From: "Kalra, Ashish" <ashish.kalra@....com>
To: seanjc@...gle.com, pbonzini@...hat.com, tglx@...utronix.de,
 mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
 hpa@...or.com, thomas.lendacky@....com, john.allen@....com,
 herbert@...dor.apana.org.au
Cc: michael.roth@....com, dionnaglaze@...gle.com, nikunj@....com,
 ardb@...nel.org, kevinloughlin@...gle.com, Neeraj.Upadhyay@....com,
 aik@....com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-crypto@...r.kernel.org, linux-coco@...ts.linux.dev
Subject: Re: [PATCH v6 7/8] KVM: SVM: Add support to initialize SEV/SNP
 functionality in KVM

Hello Sean,

On 3/6/2025 5:11 PM, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@....com>
> 
> Move platform initialization of SEV/SNP from CCP driver probe time to
> KVM module load time so that KVM can do SEV/SNP platform initialization
> explicitly if it actually wants to use SEV/SNP functionality.
> 
> Add support for KVM to explicitly call into the CCP driver at load time
> to initialize SEV/SNP. If required, this behavior can be altered with KVM
> module parameters to not do SEV/SNP platform initialization at module load
> time. Additionally, a corresponding SEV/SNP platform shutdown is invoked
> during KVM module unload time.
> 
> Continue to support SEV deferred initialization as the user may have the
> file containing SEV persistent data for SEV INIT_EX available only later
> after module load/init.
> 
> Suggested-by: Sean Christopherson <seanjc@...gle.com>
> Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> ---
>  arch/x86/kvm/svm/sev.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 0bc708ee2788..7be4e1647903 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -2933,6 +2933,7 @@ void __init sev_set_cpu_caps(void)
>  void __init sev_hardware_setup(void)
>  {
>  	unsigned int eax, ebx, ecx, edx, sev_asid_count, sev_es_asid_count;
> +	struct sev_platform_init_args init_args = {0};
>  	bool sev_snp_supported = false;
>  	bool sev_es_supported = false;
>  	bool sev_supported = false;
> @@ -3059,6 +3060,15 @@ void __init sev_hardware_setup(void)
>  	sev_supported_vmsa_features = 0;
>  	if (sev_es_debug_swap_enabled)
>  		sev_supported_vmsa_features |= SVM_SEV_FEAT_DEBUG_SWAP;
> +
> +	if (!sev_enabled)
> +		return;
> +
> +	/*
> +	 * Do both SNP and SEV initialization at KVM module load.
> +	 */
> +	init_args.probe = true;
> +	sev_platform_init(&init_args);
>  }
>  
>  void sev_hardware_unsetup(void)
> @@ -3074,6 +3084,8 @@ void sev_hardware_unsetup(void)
>  
>  	misc_cg_set_capacity(MISC_CG_RES_SEV, 0);
>  	misc_cg_set_capacity(MISC_CG_RES_SEV_ES, 0);
> +
> +	sev_platform_shutdown();
>  }
>  
>  int sev_cpu_init(struct svm_cpu_data *sd)

I am looking for feedback on this patch.

Can we go ahead and merge this patch or are you looking for anything
to be changed specifically for this patch ?

The SNP CipherTextHiding support and SEV firmware hotloading patch-sets
are gated on this patch series, so it will be nice to have some feedback
on moving this patch-set forward.

Thanks,
Ashish