kvm: svm: Always set svm->last_cpu on VMRUN

Previously, this field was only set when using SEV. Set it for all
vCPU configurations, so that it can be communicated to userspace for
diagnosing potential hardware errors.
Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Oliver Upton <oupton@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Message-Id: <20200603235623.245638-3-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/sev.c

@@ -1189,7 +1189,6 @@ void pre_sev_run(struct vcpu_svm *svm, int cpu)
 	    svm->last_cpu == cpu)
 		return;
 
-	svm->last_cpu = cpu;
 	sd->sev_vmcbs[asid] = svm->vmcb;
 	svm->vmcb->control.tlb_ctl = TLB_CONTROL_FLUSH_ASID;
 	mark_dirty(svm->vmcb, VMCB_ASID);

arch/x86/kvm/svm/svm.c

@@ -3396,6 +3396,7 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
 	 */
 	x86_spec_ctrl_set_guest(svm->spec_ctrl, svm->virt_spec_ctrl);
 
+	svm->last_cpu = vcpu->cpu;
 	__svm_vcpu_run(svm->vmcb_pa, (unsigned long *)&svm->vcpu.arch.regs);
 
 #ifdef CONFIG_X86_64