KVM: SVM: do not allocate struct svm_cpu_data dynamically

The svm_data percpu variable is a pointer, but it is allocated via
svm_hardware_setup() when KVM is loaded.  Unlike hardware_enable()
this means that it is never NULL for the whole lifetime of KVM, and
static allocation does not waste any memory compared to the status quo.
It is also more efficient and more easily handled from assembly code,
so do it and don't look back.

Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: bonzini

arch/x86/kvm/svm/sev.c

@@ -196,7 +196,7 @@ static void sev_asid_free(struct kvm_sev_info *sev)
 	__set_bit(sev->asid, sev_reclaim_asid_bitmap);
 
 	for_each_possible_cpu(cpu) {
-		sd = per_cpu(svm_data, cpu);
+		sd = per_cpu_ptr(&svm_data, cpu);
 		sd->sev_vmcbs[sev->asid] = NULL;
 	}
 
@@ -2600,7 +2600,7 @@ void sev_es_unmap_ghcb(struct vcpu_svm *svm)
 
 void pre_sev_run(struct vcpu_svm *svm, int cpu)
 {
-	struct svm_cpu_data *sd = per_cpu(svm_data, cpu);
+	struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, cpu);
 	int asid = sev_get_asid(svm->vcpu.kvm);
 
 	/* Assign the asid allocated with this SEV guest */

arch/x86/kvm/svm/svm.c

@@ -245,7 +245,7 @@ struct kvm_ldttss_desc {
 	u32 zero1;
 } __attribute__((packed));
 
-DEFINE_PER_CPU(struct svm_cpu_data *, svm_data);
+DEFINE_PER_CPU(struct svm_cpu_data, svm_data);
 
 /*
  * Only MSR_TSC_AUX is switched via the user return hook.  EFER is switched via
@@ -581,12 +581,7 @@ static int svm_hardware_enable(void)
 		pr_err("%s: err EOPNOTSUPP on %d\n", __func__, me);
 		return -EINVAL;
 	}
-	sd = per_cpu(svm_data, me);
-	if (!sd) {
-		pr_err("%s: svm_data is NULL on %d\n", __func__, me);
-		return -EINVAL;
-	}
-
+	sd = per_cpu_ptr(&svm_data, me);
 	sd->asid_generation = 1;
 	sd->max_asid = cpuid_ebx(SVM_CPUID_FUNC) - 1;
 	sd->next_asid = sd->max_asid + 1;
@@ -646,41 +641,35 @@ static int svm_hardware_enable(void)
 
 static void svm_cpu_uninit(int cpu)
 {
-	struct svm_cpu_data *sd = per_cpu(svm_data, cpu);
+	struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, cpu);
 
-	if (!sd)
+	if (!sd->save_area)
 		return;
 
-	per_cpu(svm_data, cpu) = NULL;
 	kfree(sd->sev_vmcbs);
 	__free_page(sd->save_area);
-	kfree(sd);
+	sd->save_area = NULL;
 }
 
 static int svm_cpu_init(int cpu)
 {
-	struct svm_cpu_data *sd;
+	struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, cpu);
 	int ret = -ENOMEM;
 
-	sd = kzalloc(sizeof(struct svm_cpu_data), GFP_KERNEL);
-	if (!sd)
-		return ret;
+	memset(sd, 0, sizeof(struct svm_cpu_data));
 	sd->save_area = alloc_page(GFP_KERNEL | __GFP_ZERO);
 	if (!sd->save_area)
-		goto free_cpu_data;
+		return ret;
 
 	ret = sev_cpu_init(sd);
 	if (ret)
 		goto free_save_area;
 
-	per_cpu(svm_data, cpu) = sd;
-
 	return 0;
 
 free_save_area:
 	__free_page(sd->save_area);
-free_cpu_data:
-	kfree(sd);
+	sd->save_area = NULL;
 	return ret;
 
 }
@@ -1424,7 +1413,7 @@ static void svm_clear_current_vmcb(struct vmcb *vmcb)
 	int i;
 
 	for_each_online_cpu(i)
-		cmpxchg(&per_cpu(svm_data, i)->current_vmcb, vmcb, NULL);
+		cmpxchg(per_cpu_ptr(&svm_data.current_vmcb, i), vmcb, NULL);
 }
 
 static void svm_vcpu_free(struct kvm_vcpu *vcpu)
@@ -1449,7 +1438,7 @@ static void svm_vcpu_free(struct kvm_vcpu *vcpu)
 static void svm_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
-	struct svm_cpu_data *sd = per_cpu(svm_data, vcpu->cpu);
+	struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, vcpu->cpu);
 
 	if (sev_es_guest(vcpu->kvm))
 		sev_es_unmap_ghcb(svm);
@@ -1486,7 +1475,7 @@ static void svm_prepare_host_switch(struct kvm_vcpu *vcpu)
 static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
-	struct svm_cpu_data *sd = per_cpu(svm_data, cpu);
+	struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, cpu);
 
 	if (sd->current_vmcb != svm->vmcb) {
 		sd->current_vmcb = svm->vmcb;
@@ -3442,15 +3431,15 @@ static int svm_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 
 static void reload_tss(struct kvm_vcpu *vcpu)
 {
-	struct svm_cpu_data *sd = per_cpu(svm_data, vcpu->cpu);
+	struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, vcpu->cpu);
 
 	sd->tss_desc->type = 9; /* available 32/64-bit TSS */
 	load_TR_desc();
 }
 
 static void pre_svm_run(struct kvm_vcpu *vcpu)
 {
-	struct svm_cpu_data *sd = per_cpu(svm_data, vcpu->cpu);
+	struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, vcpu->cpu);
 	struct vcpu_svm *svm = to_svm(vcpu);
 
 	/*
@@ -3919,7 +3908,7 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu)
 	if (sev_es_guest(vcpu->kvm)) {
 		__svm_sev_es_vcpu_run(svm);
 	} else {
-		struct svm_cpu_data *sd = per_cpu(svm_data, vcpu->cpu);
+		struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, vcpu->cpu);
 
 		/*
 		 * Use a single vmcb (vmcb01 because it's always valid) for

arch/x86/kvm/svm/svm.h

@@ -293,7 +293,7 @@ struct svm_cpu_data {
 	struct vmcb **sev_vmcbs;
 };
 
-DECLARE_PER_CPU(struct svm_cpu_data *, svm_data);
+DECLARE_PER_CPU(struct svm_cpu_data, svm_data);
 
 void recalc_intercepts(struct vcpu_svm *svm);