static int mem_event_grab_slot(struct mem_event_domain *med, int foreign)
{
unsigned int avail_req;
if ( !med->ring_page )
return -ENOSYS;
mem_event_ring_lock(med);
avail_req = mem_event_ring_available(med);
if ( avail_req == 0 )
{
mem_event_ring_unlock(med);
return -EBUSY;
}
if ( !foreign )
med->target_producers++;
else
med->foreign_producers++;
mem_event_ring_unlock(med);
return 0;
}
int mem_event_get_response(struct domain *d, struct mem_event_domain *med, mem_event_response_t *rsp)
{
mem_event_front_ring_t *front_ring;
RING_IDX rsp_cons;
mem_event_ring_lock(med);
front_ring = &med->front_ring;
rsp_cons = front_ring->rsp_cons;
if ( !RING_HAS_UNCONSUMED_RESPONSES(front_ring) )
{
mem_event_ring_unlock(med);
return 0;
}
/* Copy response */
memcpy(rsp, RING_GET_RESPONSE(front_ring, rsp_cons), sizeof(*rsp));
rsp_cons++;
/* Update ring */
front_ring->rsp_cons = rsp_cons;
front_ring->sring->rsp_event = rsp_cons + 1;
/* Kick any waiters -- since we've just consumed an event,
* there may be additional space available in the ring. */
mem_event_wake(d, med);
mem_event_ring_unlock(med);
return 1;
}
static int mem_event_disable(struct domain *d, struct mem_event_domain *med)
{
if ( med->ring_page )
{
struct vcpu *v;
mem_event_ring_lock(med);
if ( !list_empty(&med->wq.list) )
{
mem_event_ring_unlock(med);
return -EBUSY;
}
/* Free domU's event channel and leave the other one unbound */
free_xen_event_channel(d, med->xen_port);
/* Unblock all vCPUs */
for_each_vcpu ( d, v )
{
if ( test_and_clear_bit(med->pause_flag, &v->pause_flags) )
{
vcpu_unpause(v);
med->blocked--;
}
}
destroy_ring_for_helper(&med->ring_page,
med->ring_pg_struct);
mem_event_ring_unlock(med);
}
return 0;
}
int mem_event_check_ring(struct domain *d)
{
struct vcpu *curr = current;
int free_requests;
int ring_full;
if ( !d->mem_event.ring_page )
return -1;
mem_event_ring_lock(d);
free_requests = RING_FREE_REQUESTS(&d->mem_event.front_ring);
if ( unlikely(free_requests < 2) )
{
gdprintk(XENLOG_INFO, "free request slots: %d\n", free_requests);
WARN_ON(free_requests == 0);
}
ring_full = free_requests < MEM_EVENT_RING_THRESHOLD ? 1 : 0;
if ( (curr->domain->domain_id == d->domain_id) && ring_full )
{
set_bit(_VPF_mem_event, &curr->pause_flags);
vcpu_sleep_nosync(curr);
}
mem_event_ring_unlock(d);
return ring_full;
}
/*
* This must be preceded by a call to claim_slot(), and is guaranteed to
* succeed. As a side-effect however, the vCPU may be paused if the ring is
* overly full and its continued execution would cause stalling and excessive
* waiting. The vCPU will be automatically unpaused when the ring clears.
*/
void mem_event_put_request(struct domain *d,
struct mem_event_domain *med,
mem_event_request_t *req)
{
mem_event_front_ring_t *front_ring;
int free_req;
unsigned int avail_req;
RING_IDX req_prod;
if ( current->domain != d )
{
req->flags |= MEM_EVENT_FLAG_FOREIGN;
#ifndef NDEBUG
if ( !(req->flags & MEM_EVENT_FLAG_VCPU_PAUSED) )
gdprintk(XENLOG_G_WARNING, "d%dv%d was not paused.\n",
d->domain_id, req->vcpu_id);
#endif
}
mem_event_ring_lock(med);
/* Due to the reservations, this step must succeed. */
front_ring = &med->front_ring;
free_req = RING_FREE_REQUESTS(front_ring);
ASSERT(free_req > 0);
/* Copy request */
req_prod = front_ring->req_prod_pvt;
memcpy(RING_GET_REQUEST(front_ring, req_prod), req, sizeof(*req));
req_prod++;
/* Update ring */
front_ring->req_prod_pvt = req_prod;
RING_PUSH_REQUESTS(front_ring);
/* We've actually *used* our reservation, so release the slot. */
mem_event_release_slot(d, med);
/* Give this vCPU a black eye if necessary, on the way out.
* See the comments above wake_blocked() for more information
* on how this mechanism works to avoid waiting. */
avail_req = mem_event_ring_available(med);
if( current->domain == d && avail_req < d->max_vcpus )
mem_event_mark_and_pause(current, med);
mem_event_ring_unlock(med);
notify_via_xen_event_channel(d, med->xen_port);
}
void mem_event_get_response(struct domain *d, mem_event_response_t *rsp)
{
mem_event_front_ring_t *front_ring;
RING_IDX rsp_cons;
mem_event_ring_lock(d);
front_ring = &d->mem_event.front_ring;
rsp_cons = front_ring->rsp_cons;
/* Copy response */
memcpy(rsp, RING_GET_RESPONSE(front_ring, rsp_cons), sizeof(*rsp));
rsp_cons++;
/* Update ring */
front_ring->rsp_cons = rsp_cons;
front_ring->sring->rsp_event = rsp_cons + 1;
mem_event_ring_unlock(d);
}
void mem_event_put_request(struct domain *d, mem_event_request_t *req)
{
mem_event_front_ring_t *front_ring;
RING_IDX req_prod;
mem_event_ring_lock(d);
front_ring = &d->mem_event.front_ring;
req_prod = front_ring->req_prod_pvt;
/* Copy request */
memcpy(RING_GET_REQUEST(front_ring, req_prod), req, sizeof(*req));
req_prod++;
/* Update ring */
front_ring->req_prod_pvt = req_prod;
RING_PUSH_REQUESTS(front_ring);
mem_event_ring_unlock(d);
notify_via_xen_event_channel(d, d->mem_event.xen_port);
}
static int mem_event_enable(
struct domain *d,
xen_domctl_mem_event_op_t *mec,
struct mem_event_domain *med,
int pause_flag,
int param,
xen_event_channel_notification_t notification_fn)
{
int rc;
unsigned long ring_gfn = d->arch.hvm_domain.params[param];
/* Only one helper at a time. If the helper crashed,
* the ring is in an undefined state and so is the guest.
*/
if ( med->ring_page )
return -EBUSY;
/* The parameter defaults to zero, and it should be
* set to something */
if ( ring_gfn == 0 )
return -ENOSYS;
mem_event_ring_lock_init(med);
mem_event_ring_lock(med);
rc = prepare_ring_for_helper(d, ring_gfn, &med->ring_pg_struct,
&med->ring_page);
if ( rc < 0 )
goto err;
/* Set the number of currently blocked vCPUs to 0. */
med->blocked = 0;
/* Allocate event channel */
rc = alloc_unbound_xen_event_channel(d, 0, current->domain->domain_id,
notification_fn);
if ( rc < 0 )
goto err;
med->xen_port = mec->port = rc;
/* Prepare ring buffer */
FRONT_RING_INIT(&med->front_ring,
(mem_event_sring_t *)med->ring_page,
PAGE_SIZE);
/* Save the pause flag for this particular ring. */
med->pause_flag = pause_flag;
/* Initialize the last-chance wait queue. */
init_waitqueue_head(&med->wq);
mem_event_ring_unlock(med);
return 0;
err:
destroy_ring_for_helper(&med->ring_page,
med->ring_pg_struct);
mem_event_ring_unlock(med);
return rc;
}
void mem_event_cancel_slot(struct domain *d, struct mem_event_domain *med)
{
mem_event_ring_lock(med);
mem_event_release_slot(d, med);
mem_event_ring_unlock(med);
}