linux-kernel - Re: [PATCH Part2 RFC v2 21/37] KVM: SVM: Add KVM_SNP

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Date:   Thu, 6 May 2021 14:25:50 -0600
From:   Peter Gonda <pgonda@...gle.com>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        kvm list <kvm@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, jroedel@...e.de,
        "Lendacky, Thomas" <thomas.lendacky@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...el.com>,
        David Rientjes <rientjes@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>, peterz@...radead.org,
        "H. Peter Anvin" <hpa@...or.com>, tony.luck@...el.com
Subject: Re: [PATCH Part2 RFC v2 21/37] KVM: SVM: Add KVM_SNP_INIT command

On Fri, Apr 30, 2021 at 6:44 AM Brijesh Singh <brijesh.singh@....com> wrote:
>
> The KVM_SNP_INIT command is used by the hypervisor to initialize the
> SEV-SNP platform context. In a typical workflow, this command should be the
> first command issued. When creating SEV-SNP guest, the VMM must use this
> command instead of the KVM_SEV_INIT or KVM_SEV_ES_INIT.
>
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> ---
>  arch/x86/kvm/svm/sev.c   | 18 ++++++++++++++++--
>  include/uapi/linux/kvm.h |  3 +++
>  2 files changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 200d227f9232..ea74dd9e03d3 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -230,8 +230,9 @@ static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
>
>  static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
>  {
> +       bool es_active = (argp->id == KVM_SEV_ES_INIT || argp->id == KVM_SEV_SNP_INIT);
>         struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
> -       bool es_active = argp->id == KVM_SEV_ES_INIT;
> +       bool snp_active = argp->id == KVM_SEV_SNP_INIT;
>         int asid, ret;
>
>         if (kvm->created_vcpus)
> @@ -242,12 +243,16 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
>                 return ret;
>
>         sev->es_active = es_active;
> +       sev->snp_active = snp_active;
>         asid = sev_asid_new(sev);
>         if (asid < 0)
>                 goto e_no_asid;
>         sev->asid = asid;
>
> -       ret = sev_platform_init(&argp->error);
> +       if (snp_active)
> +               ret = sev_snp_init(&argp->error);
> +       else
> +               ret = sev_platform_init(&argp->error);
>         if (ret)
>                 goto e_free;
>
> @@ -583,6 +588,9 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
>         save->pkru = svm->vcpu.arch.pkru;
>         save->xss  = svm->vcpu.arch.ia32_xss;
>
> +       if (sev_snp_guest(svm->vcpu.kvm))
> +               save->sev_features |= SVM_SEV_FEATURES_SNP_ACTIVE;
> +
>         /*
>          * SEV-ES will use a VMSA that is pointed to by the VMCB, not
>          * the traditional VMSA that is part of the VMCB. Copy the
> @@ -1525,6 +1533,12 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
>         }
>
>         switch (sev_cmd.id) {
> +       case KVM_SEV_SNP_INIT:
> +               if (!sev_snp_enabled) {
> +                       r = -ENOTTY;
> +                       goto out;
> +               }
> +               fallthrough;
>         case KVM_SEV_ES_INIT:
>                 if (!sev_es_enabled) {
>                         r = -ENOTTY;
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 3fd9a7e9d90c..aaa2d62f09b5 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1678,6 +1678,9 @@ enum sev_cmd_id {
>         /* Guest Migration Extension */
>         KVM_SEV_SEND_CANCEL,
>
> +       /* SNP specific commands */
> +       KVM_SEV_SNP_INIT,
> +

Do you want to reserve some more enum values for SEV in case
additional functionality is added, or is this very unlikely?

>         KVM_SEV_NR_MAX,
>  };
>
> --
> 2.17.1
>