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    SubjectRe: [PATCH v6 06/18] xen/pvcalls: handle commands from the frontend
    On Tue, 4 Jul 2017, Juergen Gross wrote:
    > On 03/07/17 23:08, Stefano Stabellini wrote:
    > > When the other end notifies us that there are commands to be read
    > > (pvcalls_back_event), wake up the backend thread to parse the command.
    > >
    > > The command ring works like most other Xen rings, so use the usual
    > > ring macros to read and write to it. The functions implementing the
    > > commands are empty stubs for now.
    > >
    > > Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
    > > CC: boris.ostrovsky@oracle.com
    > > CC: jgross@suse.com
    > > ---
    > > drivers/xen/pvcalls-back.c | 144 ++++++++++++++++++++++++++++++++++++++++-----
    > > 1 file changed, 129 insertions(+), 15 deletions(-)
    > >
    > > diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
    > > index e4c2e46..9e00971 100644
    > > --- a/drivers/xen/pvcalls-back.c
    > > +++ b/drivers/xen/pvcalls-back.c
    > > @@ -47,16 +47,135 @@ struct pvcalls_fedata {
    > > struct list_head socket_mappings;
    > > struct radix_tree_root socketpass_mappings;
    > > struct semaphore socket_lock;
    > > - struct workqueue_struct *wq;
    > > - struct work_struct register_work;

    I realize that this changes should actually be folded in the previous
    patch (wq and register_work shouldn't be added in the first place). I'll
    fix the patches.


    > > };
    > >
    > > -static void pvcalls_back_work(struct work_struct *work)
    > > +static int pvcalls_back_socket(struct xenbus_device *dev,
    > > + struct xen_pvcalls_request *req)
    > > {
    > > + return 0;
    > > +}
    > > +
    > > +static int pvcalls_back_connect(struct xenbus_device *dev,
    > > + struct xen_pvcalls_request *req)
    > > +{
    > > + return 0;
    > > +}
    > > +
    > > +static int pvcalls_back_release(struct xenbus_device *dev,
    > > + struct xen_pvcalls_request *req)
    > > +{
    > > + return 0;
    > > +}
    > > +
    > > +static int pvcalls_back_bind(struct xenbus_device *dev,
    > > + struct xen_pvcalls_request *req)
    > > +{
    > > + return 0;
    > > +}
    > > +
    > > +static int pvcalls_back_listen(struct xenbus_device *dev,
    > > + struct xen_pvcalls_request *req)
    > > +{
    > > + return 0;
    > > +}
    > > +
    > > +static int pvcalls_back_accept(struct xenbus_device *dev,
    > > + struct xen_pvcalls_request *req)
    > > +{
    > > + return 0;
    > > +}
    > > +
    > > +static int pvcalls_back_poll(struct xenbus_device *dev,
    > > + struct xen_pvcalls_request *req)
    > > +{
    > > + return 0;
    > > +}
    > > +
    > > +static int pvcalls_back_handle_cmd(struct xenbus_device *dev,
    > > + struct xen_pvcalls_request *req)
    > > +{
    > > + int ret = 0;
    > > +
    > > + switch (req->cmd) {
    > > + case PVCALLS_SOCKET:
    > > + ret = pvcalls_back_socket(dev, req);
    > > + break;
    > > + case PVCALLS_CONNECT:
    > > + ret = pvcalls_back_connect(dev, req);
    > > + break;
    > > + case PVCALLS_RELEASE:
    > > + ret = pvcalls_back_release(dev, req);
    > > + break;
    > > + case PVCALLS_BIND:
    > > + ret = pvcalls_back_bind(dev, req);
    > > + break;
    > > + case PVCALLS_LISTEN:
    > > + ret = pvcalls_back_listen(dev, req);
    > > + break;
    > > + case PVCALLS_ACCEPT:
    > > + ret = pvcalls_back_accept(dev, req);
    > > + break;
    > > + case PVCALLS_POLL:
    > > + ret = pvcalls_back_poll(dev, req);
    > > + break;
    > > + default:
    > > + {
    > > + struct pvcalls_fedata *fedata;
    > > + struct xen_pvcalls_response *rsp;
    > > +
    > > + fedata = dev_get_drvdata(&dev->dev);
    > > + rsp = RING_GET_RESPONSE(
    > > + &fedata->ring, fedata->ring.rsp_prod_pvt++);
    > > + rsp->req_id = req->req_id;
    > > + rsp->cmd = req->cmd;
    > > + rsp->ret = -ENOTSUPP;
    > > + break;
    > > + }
    > > + }
    > > + return ret;
    > > +}
    > > +
    > > +static void pvcalls_back_work(struct pvcalls_fedata *fedata)
    > > +{
    > > + int notify, notify_all = 0, more = 1;
    > > + struct xen_pvcalls_request req;
    > > + struct xenbus_device *dev = fedata->dev;
    > > +
    > > + while (more) {
    > > + while (RING_HAS_UNCONSUMED_REQUESTS(&fedata->ring)) {
    > > + RING_COPY_REQUEST(&fedata->ring,
    > > + fedata->ring.req_cons++,
    > > + &req);
    > > +
    > > + if (!pvcalls_back_handle_cmd(dev, &req)) {
    > > + RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(
    > > + &fedata->ring, notify);
    > > + notify_all += notify;
    > > + }
    > > + }
    > > +
    > > + if (notify_all) {
    > > + notify_remote_via_irq(fedata->irq);
    > > + notify_all = 0;
    > > + }
    > > +
    > > + RING_FINAL_CHECK_FOR_REQUESTS(&fedata->ring, more);
    > > + }
    > > }
    > >
    > > static irqreturn_t pvcalls_back_event(int irq, void *dev_id)
    > > {
    > > + struct xenbus_device *dev = dev_id;
    > > + struct pvcalls_fedata *fedata = NULL;
    > > +
    > > + if (dev == NULL)
    > > + return IRQ_HANDLED;
    > > +
    > > + fedata = dev_get_drvdata(&dev->dev);
    > > + if (fedata == NULL)
    > > + return IRQ_HANDLED;
    > > +
    > > + pvcalls_back_work(fedata);
    > > return IRQ_HANDLED;
    > > }
    > >
    > > @@ -87,18 +206,15 @@ static int backend_connect(struct xenbus_device *dev)
    > > goto error;
    > > }
    > >
    > > - err = bind_interdomain_evtchn_to_irqhandler(dev->otherend_id, evtchn,
    > > - pvcalls_back_event, 0,
    > > - "pvcalls-backend", dev);
    > > + err = bind_interdomain_evtchn_to_irq(dev->otherend_id, evtchn);
    > > if (err < 0)
    > > goto error;
    > > fedata->irq = err;
    > > -
    > > - fedata->wq = alloc_workqueue("pvcalls_back_wq", WQ_UNBOUND, 1);
    > > - if (!fedata->wq) {
    > > - err = -ENOMEM;
    > > +
    > > + err = request_threaded_irq(fedata->irq, NULL, pvcalls_back_event,
    > > + IRQF_ONESHOT, "pvcalls-back", dev);
    > > + if (err < 0)
    > > goto error;
    > > - }
    > >
    > > err = xenbus_map_ring_valloc(dev, &ring_ref, 1, (void**)&fedata->sring);
    > > if (err < 0)
    > > @@ -107,7 +223,6 @@ static int backend_connect(struct xenbus_device *dev)
    > > BACK_RING_INIT(&fedata->ring, fedata->sring, XEN_PAGE_SIZE * 1);
    > > fedata->dev = dev;
    > >
    > > - INIT_WORK(&fedata->register_work, pvcalls_back_work);
    > > INIT_LIST_HEAD(&fedata->socket_mappings);
    > > INIT_RADIX_TREE(&fedata->socketpass_mappings, GFP_KERNEL);
    > > sema_init(&fedata->socket_lock, 1);
    > > @@ -116,15 +231,14 @@ static int backend_connect(struct xenbus_device *dev)
    > > down(&pvcalls_back_global.frontends_lock);
    > > list_add_tail(&fedata->list, &pvcalls_back_global.frontends);
    > > up(&pvcalls_back_global.frontends_lock);
    > > - queue_work(fedata->wq, &fedata->register_work);
    > > +
    > > + pvcalls_back_work(fedata);
    >
    > Is this call really necessary? I believe this is racy in case an event
    > is coming in at the same time.

    No, it is not. I'll remove it.


    > >
    > > return 0;
    > >
    > > error:
    > > if (fedata->sring != NULL)
    > > xenbus_unmap_ring_vfree(dev, fedata->sring);
    > > - if (fedata->wq)
    > > - destroy_workqueue(fedata->wq);
    > > unbind_from_irqhandler(fedata->irq, dev);
    >
    > Is it secure to unbind the irq handler _after_ unmapping the ring?

    Good point, I'll change the order.

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