Re: [PATCH v11 5/8] KVM: SEV: Move init of SNP guest state into sev_init_vmcb()

["Nikunj A. Dadhania" <nikunj@amd.com>]

On 8/20/2025 5:18 AM, Sean Christopherson wrote:
> Move the initialization of SNP guest state from svm_vcpu_reset() into
> sev_init_vmcb() to reduce the number of paths that deal with INIT/RESET
> for SEV+ vCPUs from 4+ to 1.  Plumb in @init_event as necessary.
> 
> Opportunistically check for an SNP guest outside of
> sev_snp_init_protected_guest_state() so that sev_init_vmcb() is consistent
> with respect to checking for SEV-ES+ and SNP+ guests.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Reviewed-by: Nikunj A Dadhania <nikunj@amd.com>

> ---
>  arch/x86/kvm/svm/sev.c | 16 +++++++++-------
>  arch/x86/kvm/svm/svm.c |  9 +++------
>  arch/x86/kvm/svm/svm.h |  4 +---
>  3 files changed, 13 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index c17cc4eb0fe1..c5726b091680 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1975,7 +1975,7 @@ static void sev_migrate_from(struct kvm *dst_kvm, struct kvm *src_kvm)
>  	kvm_for_each_vcpu(i, dst_vcpu, dst_kvm) {
>  		dst_svm = to_svm(dst_vcpu);
>  
> -		sev_init_vmcb(dst_svm);
> +		sev_init_vmcb(dst_svm, false);
>  
>  		if (!dst->es_active)
>  			continue;
> @@ -3887,7 +3887,7 @@ static int snp_begin_psc(struct vcpu_svm *svm, struct psc_buffer *psc)
>  /*
>   * Invoked as part of svm_vcpu_reset() processing of an init event.
>   */
> -void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu)
> +static void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu)
>  {
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  	struct kvm_memory_slot *slot;
> @@ -3895,9 +3895,6 @@ void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu)
>  	kvm_pfn_t pfn;
>  	gfn_t gfn;
>  
> -	if (!sev_snp_guest(vcpu->kvm))
> -		return;
> -
>  	guard(mutex)(&svm->sev_es.snp_vmsa_mutex);
>  
>  	if (!svm->sev_es.snp_ap_waiting_for_reset)
> @@ -4546,8 +4543,10 @@ static void sev_es_init_vmcb(struct vcpu_svm *svm)
>  	svm_clr_intercept(svm, INTERCEPT_XSETBV);
>  }
>  
> -void sev_init_vmcb(struct vcpu_svm *svm)
> +void sev_init_vmcb(struct vcpu_svm *svm, bool init_event)
>  {
> +	struct kvm_vcpu *vcpu = &svm->vcpu;
> +
>  	svm->vmcb->control.nested_ctl |= SVM_NESTED_CTL_SEV_ENABLE;
>  	clr_exception_intercept(svm, UD_VECTOR);
>  
> @@ -4557,7 +4556,10 @@ void sev_init_vmcb(struct vcpu_svm *svm)
>  	 */
>  	clr_exception_intercept(svm, GP_VECTOR);
>  
> -	if (sev_es_guest(svm->vcpu.kvm))
> +	if (init_event && sev_snp_guest(vcpu->kvm))
> +		sev_snp_init_protected_guest_state(vcpu);
> +
> +	if (sev_es_guest(vcpu->kvm))
>  		sev_es_init_vmcb(svm);
>  }
>  
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 3d4c14e0244f..8ed135dbd649 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -1083,7 +1083,7 @@ static void svm_recalc_intercepts_after_set_cpuid(struct kvm_vcpu *vcpu)
>  	svm_recalc_msr_intercepts(vcpu);
>  }
>  
> -static void init_vmcb(struct kvm_vcpu *vcpu)
> +static void init_vmcb(struct kvm_vcpu *vcpu, bool init_event)
>  {
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  	struct vmcb *vmcb = svm->vmcb01.ptr;
> @@ -1221,7 +1221,7 @@ static void init_vmcb(struct kvm_vcpu *vcpu)
>  		svm_set_intercept(svm, INTERCEPT_BUSLOCK);
>  
>  	if (sev_guest(vcpu->kvm))
> -		sev_init_vmcb(svm);
> +		sev_init_vmcb(svm, init_event);
>  
>  	svm_hv_init_vmcb(vmcb);
>  
> @@ -1256,10 +1256,7 @@ static void svm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>  	svm->spec_ctrl = 0;
>  	svm->virt_spec_ctrl = 0;
>  
> -	if (init_event)
> -		sev_snp_init_protected_guest_state(vcpu);
> -
> -	init_vmcb(vcpu);
> +	init_vmcb(vcpu, init_event);
>  
>  	if (!init_event)
>  		__svm_vcpu_reset(vcpu);
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index cf2569b5451a..321480ebe62f 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -826,7 +826,7 @@ void avic_refresh_virtual_apic_mode(struct kvm_vcpu *vcpu);
>  /* sev.c */
>  
>  int pre_sev_run(struct vcpu_svm *svm, int cpu);
> -void sev_init_vmcb(struct vcpu_svm *svm);
> +void sev_init_vmcb(struct vcpu_svm *svm, bool init_event);
>  void sev_vcpu_after_set_cpuid(struct vcpu_svm *svm);
>  int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in);
>  void sev_es_vcpu_reset(struct vcpu_svm *svm);
> @@ -864,7 +864,6 @@ int sev_cpu_init(struct svm_cpu_data *sd);
>  int sev_dev_get_attr(u32 group, u64 attr, u64 *val);
>  extern unsigned int max_sev_asid;
>  void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code);
> -void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu);
>  int sev_gmem_prepare(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, int max_order);
>  void sev_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end);
>  int sev_private_max_mapping_level(struct kvm *kvm, kvm_pfn_t pfn);
> @@ -891,7 +890,6 @@ static inline int sev_cpu_init(struct svm_cpu_data *sd) { return 0; }
>  static inline int sev_dev_get_attr(u32 group, u64 attr, u64 *val) { return -ENXIO; }
>  #define max_sev_asid 0
>  static inline void sev_handle_rmp_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u64 error_code) {}
> -static inline void sev_snp_init_protected_guest_state(struct kvm_vcpu *vcpu) {}
>  static inline int sev_gmem_prepare(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, int max_order)
>  {
>  	return 0;