Commit c2b8cdfa authored by David Woodhouse's avatar David Woodhouse Committed by Paolo Bonzini
Browse files

KVM: x86/xen: Only do in-kernel acceleration of hypercalls for guest CPL0 



There are almost no hypercalls which are valid from CPL > 0, and definitely
none which are handled by the kernel.

Fixes: 2fd6df2f ("KVM: x86/xen: intercept EVTCHNOP_send from guests")
Reported-by: default avatarMichal Luczaj <mhal@rbox.co>
Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: default avatarSean Christopherson <seanjc@google.com>
Cc: stable@kernel.org
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 4ea9439f

arch/x86/kvm/xen.c

+11 −1
Original line number Diff line number Diff line
@@ -1227,6 +1227,7 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu) 
	bool longmode;

	u64 input, params[6], r = -ENOSYS;

	bool handled = false;

	u8 cpl;



	input = (u64)kvm_register_read(vcpu, VCPU_REGS_RAX);
@@ -1254,9 +1255,17 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu) 
		params[5] = (u64)kvm_r9_read(vcpu);

	}

#endif

	cpl = static_call(kvm_x86_get_cpl)(vcpu);

	trace_kvm_xen_hypercall(input, params[0], params[1], params[2],

				params[3], params[4], params[5]);



	/*

	 * Only allow hypercall acceleration for CPL0. The rare hypercalls that

	 * are permitted in guest userspace can be handled by the VMM.

	 */

	if (unlikely(cpl > 0))

		goto handle_in_userspace;



	switch (input) {

	case __HYPERVISOR_xen_version:

		if (params[0] == XENVER_version && vcpu->kvm->arch.xen.xen_version) {
@@ -1291,10 +1300,11 @@ int kvm_xen_hypercall(struct kvm_vcpu *vcpu) 
	if (handled)

		return kvm_xen_hypercall_set_result(vcpu, r);



handle_in_userspace:

	vcpu->run->exit_reason = KVM_EXIT_XEN;

	vcpu->run->xen.type = KVM_EXIT_XEN_HCALL;

	vcpu->run->xen.u.hcall.longmode = longmode;

	vcpu->run->xen.u.hcall.cpl = static_call(kvm_x86_get_cpl)(vcpu);

	vcpu->run->xen.u.hcall.cpl = cpl;

	vcpu->run->xen.u.hcall.input = input;

	vcpu->run->xen.u.hcall.params[0] = params[0];

	vcpu->run->xen.u.hcall.params[1] = params[1];