linux-kernel - Re: [PATCH v3 6/7] KVM: SVM: Add support to initialize SEV/SNP functionality in KVM

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Message-ID: <6241f868-98ee-592b-9475-7e6cec09d977@amd.com>
Date: Tue, 7 Jan 2025 10:42:55 -0600
From: Tom Lendacky <thomas.lendacky@....com>
To: Ashish Kalra <Ashish.Kalra@....com>, 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,
 john.allen@....com, herbert@...dor.apana.org.au, davem@...emloft.net
Cc: michael.roth@....com, dionnaglaze@...gle.com, kvm@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
 linux-coco@...ts.linux.dev
Subject: Re: [PATCH v3 6/7] KVM: SVM: Add support to initialize SEV/SNP
 functionality in KVM

On 1/3/25 14:01, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@....com>
> 
> Remove platform initialization of SEV/SNP from PSP driver probe time and

Actually, you're not removing it, yet...

> move it to KVM module load time so that KVM can do SEV/SNP platform
> initialization explicitly if it actually wants to use SEV/SNP
> functionality.
> 
> With this patch, KVM will explicitly call into the PSP driver at load time
> to initialize SEV/SNP by default but this behavior can be altered with KVM
> module parameters to not do SEV/SNP platform initialization at module load
> time if required. Additionally SEV/SNP platform shutdown is invoked during
> KVM module unload time.
> 
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> ---
>  arch/x86/kvm/svm/sev.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 943bd074a5d3..0dc8294582c6 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -444,7 +444,6 @@ static int __sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp,
>  	if (ret)
>  		goto e_no_asid;
>  
> -	init_args.probe = false;
>  	ret = sev_platform_init(&init_args);
>  	if (ret)
>  		goto e_free;
> @@ -2953,6 +2952,7 @@ 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};

Will this cause issues if KVM is built-in and INIT_EX is being used
(init_ex_path ccp parameter)? The probe parameter is used for
initialization done before the filesystem is available.

Thanks,
Tom

>  	bool sev_snp_supported = false;
>  	bool sev_es_supported = false;
>  	bool sev_supported = false;
> @@ -3069,6 +3069,16 @@ 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;
> +
> +	/*
> +	 * NOTE: Always do SNP INIT regardless of sev_snp_supported
> +	 * as SNP INIT has to be done to launch legacy SEV/SEV-ES
> +	 * VMs in case SNP is enabled system-wide.
> +	 */
> +	sev_platform_init(&init_args);
>  }
>  
>  void sev_hardware_unsetup(void)
> @@ -3084,6 +3094,9 @@ void sev_hardware_unsetup(void)
>  
>  	misc_cg_set_capacity(MISC_CG_RES_SEV, 0);
>  	misc_cg_set_capacity(MISC_CG_RES_SEV_ES, 0);
> +
> +	/* Do SEV and SNP Shutdown */
> +	sev_platform_shutdown();
>  }
>  
>  int sev_cpu_init(struct svm_cpu_data *sd)