KVM: SVM: Move RESET emulation to svm_vcpu_reset()

Move RESET emulation for SVM vCPUs to svm_vcpu_reset(), and drop an extra
init_vmcb() from svm_create_vcpu() in the process.  Hopefully KVM will
someday expose a dedicated RESET ioctl(), and in the meantime separating
"create" from "RESET" is a nice cleanup.

Keep the call to svm_switch_vmcb() so that misuse of svm->vmcb at worst
breaks the guest, e.g. premature accesses doesn't cause a NULL pointer
dereference.

Cc: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210921000303.400537-10-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/sev.c

@@ -2631,11 +2631,11 @@ void sev_es_init_vmcb(struct vcpu_svm *svm)
 	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTINTTOIP, 1, 1);
 }
 
-void sev_es_create_vcpu(struct vcpu_svm *svm)
+void sev_es_vcpu_reset(struct vcpu_svm *svm)
 {
 	/*
-	 * Set the GHCB MSR value as per the GHCB specification when creating
-	 * a vCPU for an SEV-ES guest.
+	 * Set the GHCB MSR value as per the GHCB specification when emulating
+	 * vCPU RESET for an SEV-ES guest.
 	 */
 	set_ghcb_msr(svm, GHCB_MSR_SEV_INFO(GHCB_VERSION_MAX,
 					    GHCB_VERSION_MIN,

arch/x86/kvm/svm/svm.c

@@ -1303,6 +1303,19 @@ static void init_vmcb(struct kvm_vcpu *vcpu)
 
 }
 
+static void __svm_vcpu_reset(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+
+	svm_vcpu_init_msrpm(vcpu, svm->msrpm);
+
+	svm_init_osvw(vcpu);
+	vcpu->arch.microcode_version = 0x01000065;
+
+	if (sev_es_guest(vcpu->kvm))
+		sev_es_vcpu_reset(svm);
+}
+
 static void svm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
@@ -1311,6 +1324,9 @@ static void svm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	svm->virt_spec_ctrl = 0;
 
 	init_vmcb(vcpu);
+
+	if (!init_event)
+		__svm_vcpu_reset(vcpu);
 }
 
 void svm_switch_vmcb(struct vcpu_svm *svm, struct kvm_vmcb_info *target_vmcb)
@@ -1370,24 +1386,13 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
 
 	svm->vmcb01.ptr = page_address(vmcb01_page);
 	svm->vmcb01.pa = __sme_set(page_to_pfn(vmcb01_page) << PAGE_SHIFT);
+	svm_switch_vmcb(svm, &svm->vmcb01);
 
 	if (vmsa_page)
 		svm->vmsa = page_address(vmsa_page);
 
 	svm->guest_state_loaded = false;
 
-	svm_switch_vmcb(svm, &svm->vmcb01);
-	init_vmcb(vcpu);
-
-	svm_vcpu_init_msrpm(vcpu, svm->msrpm);
-
-	svm_init_osvw(vcpu);
-	vcpu->arch.microcode_version = 0x01000065;
-
-	if (sev_es_guest(vcpu->kvm))
-		/* Perform SEV-ES specific VMCB creation updates */
-		sev_es_create_vcpu(svm);
-
 	return 0;
 
 error_free_vmsa_page:

arch/x86/kvm/svm/svm.h

@@ -562,7 +562,7 @@ void sev_free_vcpu(struct kvm_vcpu *vcpu);
 int sev_handle_vmgexit(struct kvm_vcpu *vcpu);
 int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in);
 void sev_es_init_vmcb(struct vcpu_svm *svm);
-void sev_es_create_vcpu(struct vcpu_svm *svm);
+void sev_es_vcpu_reset(struct vcpu_svm *svm);
 void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector);
 void sev_es_prepare_guest_switch(struct vcpu_svm *svm, unsigned int cpu);
 void sev_es_unmap_ghcb(struct vcpu_svm *svm);