[PATCH v2 0/1] evtchn: make EVTCHNOP_reset suitable for kexec

[Vitaly Kuznetsov <vkuznets@redhat.com>]

With the help from David Vrabel (thanks!) I was able to make event channel
rebinding work in both kexec/kdump cases. A guest should do the following
on kexec/kdump:
1) Figure out store/console interdomain mapping
2) Call PHYSDEVOP_unmap_pirq if needed
3) Call EVTCHNOP_reset
4) Rebind store/console channels with EVTCHNOP_bind_interdomain
5) Update HVM_PARAM_CONSOLE_EVTCHN/HVM_PARAM_STORE_EVTCHN

Here is an example of guest code (to be called from kexec/kdump handlers):

void xen_hvm_reset_eventchannels(void)
{
	struct evtchn_status status;
	struct physdev_unmap_pirq unmap_irq;
	struct evtchn_close close;
	struct evtchn_reset reset;
	struct evtchn_bind_interdomain int_bind;
	struct xen_hvm_param xhv;
	uint64_t store_evtchn = 0, console_evtchn = 0;
	domid_t store_domain = 0, console_domain = 0;
	evtchn_port_t store_rem_port = 0, console_rem_port = 0;
	int port, rc = -ENOENT;

	memset(&status, 0, sizeof(status));
	status.dom = DOMID_SELF;
	if (hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &store_evtchn) == 0) {
		pr_debug("xen: need to rebind store evtchn %d\n",
			 (uint32_t)store_evtchn);
		status.port = store_evtchn;
		rc = HYPERVISOR_event_channel_op(EVTCHNOP_status, &status);
		if (!rc && status.status == EVTCHNSTAT_interdomain) {
			pr_debug("xen: store port: %d, interdomain %d:%d",
				 status.port, status.u.interdomain.dom,
				 status.u.interdomain.port);
			store_domain = status.u.interdomain.dom;
			store_rem_port = status.u.interdomain.port;
		}
	}
	if (hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN, &console_evtchn) == 0) {
		pr_debug("xen: need to rebind console evtchn %d\n",
			 (uint32_t)console_evtchn);
		status.port = console_evtchn;
		rc = HYPERVISOR_event_channel_op(EVTCHNOP_status, &status);
		if (!rc && status.status == EVTCHNSTAT_interdomain) {
			pr_debug("xen: console port: %d, interdomain %d:%d",
				 status.port, status.u.interdomain.dom,
				 status.u.interdomain.port);
			console_domain = status.u.interdomain.dom;
			console_rem_port = status.u.interdomain.port;
		}
	}

	for (port = 0; port < xen_evtchn_max_channels(); port++) {
		status.dom = DOMID_SELF;
		status.port = port;
		rc = HYPERVISOR_event_channel_op(EVTCHNOP_status, &status);
		if (rc < 0)
			continue;
		if (status.status != EVTCHNSTAT_closed) {
			close.port = port;
			if (HYPERVISOR_event_channel_op(EVTCHNOP_close,
							&close) != 0)
				pr_warn("xen: failed to close evtchn %d\n",
					port);
		}

		if (status.status == EVTCHNSTAT_pirq) {
			unmap_irq.pirq = status.u.pirq;
			unmap_irq.domid = DOMID_SELF;
			pr_warn("xen: unmapping previously mapped pirq %d\n",
				unmap_irq.pirq);
			if (HYPERVISOR_physdev_op(PHYSDEVOP_unmap_pirq,
						  &unmap_irq) != 0)
				pr_warn("xen: failed to unmap pirq %d\n",
					unmap_irq.pirq);
		}
	}

	reset.dom = DOMID_SELF;
	if (HYPERVISOR_event_channel_op(EVTCHNOP_reset, &reset))
		pr_warn("failed to reset all event channels!\n");

	if (store_rem_port > 0) {
		int_bind.remote_dom = store_domain;
		int_bind.remote_port = store_rem_port;
		pr_debug("rebinding store: %d -> %d:%d\n", int_bind.local_port,
			 int_bind.remote_port, int_bind.remote_dom);
		if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain, &int_bind))
			pr_warn("failed to rebind store!\n");
		if (int_bind.local_port != store_evtchn) {
			xhv.domid = DOMID_SELF;
			xhv.index = HVM_PARAM_STORE_EVTCHN;
			xhv.value = int_bind.local_port;
			if (HYPERVISOR_hvm_op(HVMOP_set_param, &xhv)) {
				pr_warn("Cannot set HVM_PARAM_STORE_EVTCHN!\n");
			}
		}
	}

	if (console_rem_port > 0) {
		int_bind.remote_dom = console_domain;
		int_bind.remote_port = console_rem_port;
		pr_debug("rebinding console: %d -> %d:%d\n", int_bind.local_port,
			 int_bind.remote_port, int_bind.remote_dom);
		if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_interdomain, &int_bind))
			pr_warn("failed to rebind console!\n");
		if (int_bind.local_port != console_evtchn) {
			xhv.domid = DOMID_SELF;
			xhv.index = HVM_PARAM_CONSOLE_EVTCHN;
			xhv.value = int_bind.local_port;
			if (HYPERVISOR_hvm_op(HVMOP_set_param, &xhv)) {
				pr_warn("Cannot set HVM_PARAM_CONSOLE_EVTCHN!\n");
			}
		}
	}
}

Vitaly Kuznetsov (1):
  evtchn: make EVTCHNOP_reset suitable for kexec

 xen/common/event_channel.c | 11 +++++++++++
 xen/common/event_fifo.c    |  1 +
 2 files changed, 12 insertions(+)

-- 
1.9.3