KVM: SEV: Move init of SNP guest state into sev_init_vmcb()

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.

Reviewed-by: Nikunj A Dadhania <nikunj@amd.com>
Link: https://lore.kernel.org/r/20250819234833.3080255-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

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;
@@ -3887,17 +3887,14 @@ 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;
 	struct page *page;
 	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);
 }
 

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);

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;