kvm: vmx: Add last_cpu to struct vcpu_vmx

As we already do in svm, record the last logical processor on which a
vCPU has run, so that it can be communicated to userspace for
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: <20200603235623.245638-4-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

@@ -6734,6 +6734,7 @@ reenter_guest:
 	if (vcpu->arch.cr2 != read_cr2())
 		write_cr2(vcpu->arch.cr2);
 
+	vmx->last_cpu = vcpu->cpu;
 	vmx->fail = __vmx_vcpu_run(vmx, (unsigned long *)&vcpu->arch.regs,
 				   vmx->loaded_vmcs->launched);
 

arch/x86/kvm/vmx/vmx.h

@@ -300,6 +300,9 @@ struct vcpu_vmx {
 	u64 ept_pointer;
 
 	struct pt_desc pt_desc;
+
+	/* which host CPU was used for running this vcpu */
+	unsigned int last_cpu;
 };
 
 enum ept_pointers_status {