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

Tom Lendacky
2025-01-07T16:43:04Z

On 1/3/25 14:01, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@amd.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@amd.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)