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Date: Fri, 11 Aug 2017 18:55:35 -0400
From: Boris Ostrovsky <boris.ostrovsky@...cle.com>
To: Stefano Stabellini <sstabellini@...nel.org>,
xen-devel@...ts.xen.org
Cc: linux-kernel@...r.kernel.org, jgross@...e.com,
Stefano Stabellini <stefano@...reto.com>
Subject: Re: [PATCH v3 03/13] xen/pvcalls: connect to the backend
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@...reto.com>
> CC: boris.ostrovsky@...cle.com
> CC: jgross@...e.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
> + 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.
> + 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.
-boris
> + 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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