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SubjectRe: [PATCH v3 03/13] xen/pvcalls: connect to the backend
On Fri, 11 Aug 2017, Boris Ostrovsky wrote:
> On 07/31/2017 06:57 PM, Stefano Stabellini wrote:
> > Implement the probe function for the pvcalls frontend. Read the
> > supported versions, max-page-order and function-calls nodes from
> > xenstore.
> >
> > Only one frontend<->backend connection is supported at any given time
> > for a guest. Store the active frontend device to a static pointer.
> >
> > Introduce a stub functions for the event handler.
> >
> > Signed-off-by: Stefano Stabellini <stefano@aporeto.com>
> > CC: boris.ostrovsky@oracle.com
> > CC: jgross@suse.com
> > ---
> > drivers/xen/pvcalls-front.c | 130 ++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 130 insertions(+)
> >
> > diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> > index a126195..2afe36d 100644
> > --- a/drivers/xen/pvcalls-front.c
> > +++ b/drivers/xen/pvcalls-front.c
> > @@ -84,12 +84,142 @@ static int pvcalls_front_remove(struct xenbus_device *dev)
> > static int pvcalls_front_probe(struct xenbus_device *dev,
> > const struct xenbus_device_id *id)
> > {
> > + int ret = -ENOMEM, evtchn, i;
> > + unsigned int max_page_order, function_calls, len;
> > + char *versions;
> > + grant_ref_t gref_head = 0;
> > + struct xenbus_transaction xbt;
> > + struct pvcalls_bedata *bedata = NULL;
> > + struct xen_pvcalls_sring *sring;
> > +
> > + if (pvcalls_front_dev != NULL) {
> > + dev_err(&dev->dev, "only one PV Calls connection supported\n");
> > + return -EINVAL;
> > + }
> > +
> > + versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
> > + if (!len)
> > + return -EINVAL;
> > + if (strcmp(versions, "1")) {
> > + kfree(versions);
> > + return -EINVAL;
> > + }
> > + kfree(versions);
> > + max_page_order = xenbus_read_unsigned(dev->otherend,
> > + "max-page-order", 0);
> > + if (max_page_order < PVCALLS_RING_ORDER)
> > + return -ENODEV;
> > + function_calls = xenbus_read_unsigned(dev->otherend,
> > + "function-calls", 0);
> > + if (function_calls != 1)
>
> XENBUS_FUNCTIONS_CALLS

XENBUS_FUNCTIONS_CALLS is actually defined as "1". I'll add a comment
instead.


> > + return -ENODEV;
> > + pr_info("%s max-page-order is %u\n", __func__, max_page_order);
> > +
> > + bedata = kzalloc(sizeof(struct pvcalls_bedata), GFP_KERNEL);
> > + if (!bedata)
> > + return -ENOMEM;
> > +
> > + dev_set_drvdata(&dev->dev, bedata);
> > + pvcalls_front_dev = dev;
> > + init_waitqueue_head(&bedata->inflight_req);
> > + for (i = 0; i < PVCALLS_NR_REQ_PER_RING; i++)
> > + bedata->rsp[i].req_id = PVCALLS_INVALID_ID;
> > +
> > + sring = (struct xen_pvcalls_sring *) __get_free_page(GFP_KERNEL |
> > + __GFP_ZERO);
> > + if (!sring)
> > + goto error;
> > + SHARED_RING_INIT(sring);
> > + FRONT_RING_INIT(&bedata->ring, sring, XEN_PAGE_SIZE);
> > +
> > + ret = xenbus_alloc_evtchn(dev, &evtchn);
> > + if (ret)
> > + goto error;
> > +
> > + bedata->irq = bind_evtchn_to_irqhandler(evtchn,
> > + pvcalls_front_event_handler,
> > + 0, "pvcalls-frontend", dev);
> > + if (bedata->irq < 0) {
>
> In the previous patch you free up irq if it is strictly >0. Should have
> been >=0.

OK


> > + ret = bedata->irq;
> > + goto error;
> > + }
> > +
> > + ret = gnttab_alloc_grant_references(1, &gref_head);
> > + if (ret < 0)
> > + goto error;
> > + bedata->ref = gnttab_claim_grant_reference(&gref_head);
> > + if (bedata->ref < 0) {
> > + ret = bedata->ref;
> > + goto error;
> > + }
> > + gnttab_grant_foreign_access_ref(bedata->ref, dev->otherend_id,
> > + virt_to_gfn((void *)sring), 0);
> > +
> > + again:
> > + ret = xenbus_transaction_start(&xbt);
> > + if (ret) {
> > + xenbus_dev_fatal(dev, ret, "starting transaction");
> > + goto error;
> > + }
> > + ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
> > + if (ret)
> > + goto error_xenbus;
> > + ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", bedata->ref);
> > + if (ret)
> > + goto error_xenbus;
> > + ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
> > + evtchn);
> > + if (ret)
> > + goto error_xenbus;
> > + ret = xenbus_transaction_end(xbt, 0);
> > + if (ret) {
> > + if (ret == -EAGAIN)
> > + goto again;
> > + xenbus_dev_fatal(dev, ret, "completing transaction");
> > + goto error;
> > + }
> > +
> > + INIT_LIST_HEAD(&bedata->socket_mappings);
> > + INIT_LIST_HEAD(&bedata->socketpass_mappings);
> > + spin_lock_init(&bedata->pvcallss_lock);
> > + xenbus_switch_state(dev, XenbusStateInitialised);
> > +
> > return 0;
> > +
> > + error_xenbus:
> > + xenbus_transaction_end(xbt, 1);
> > + xenbus_dev_fatal(dev, ret, "writing xenstore");
> > + error:
> > + pvcalls_front_remove(dev);
>
> Going back to the previous patch --- it seems to me that on some error
> paths certain structures may not be usable in pvcalls_front_remove().
> For example, socket_mappings list is definitely not initialized.

You are right, I'll fix that.


> > + return ret;
> > }
> >
> > static void pvcalls_front_changed(struct xenbus_device *dev,
> > enum xenbus_state backend_state)
> > {
> > + switch (backend_state) {
> > + case XenbusStateReconfiguring:
> > + case XenbusStateReconfigured:
> > + case XenbusStateInitialising:
> > + case XenbusStateInitialised:
> > + case XenbusStateUnknown:
> > + break;
> > +
> > + case XenbusStateInitWait:
> > + break;
> > +
> > + case XenbusStateConnected:
> > + xenbus_switch_state(dev, XenbusStateConnected);
> > + break;
> > +
> > + case XenbusStateClosed:
> > + if (dev->state == XenbusStateClosed)
> > + break;
> > + /* Missed the backend's CLOSING state -- fallthrough */
> > + case XenbusStateClosing:
> > + xenbus_frontend_closed(dev);
> > + break;
> > + }
> > }
> >
> > static struct xenbus_driver pvcalls_front_driver = {
>

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