linux-kernel - [PATCH 03/18] xen/pvcalls: initialize the module and register the xenbus backend

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Date:   Mon, 15 May 2017 13:35:55 -0700
From:   Stefano Stabellini <sstabellini@...nel.org>
To:     xen-devel@...ts.xen.org
Cc:     linux-kernel@...r.kernel.org, sstabellini@...nel.org,
        jgross@...e.com, boris.ostrovsky@...cle.com,
        Stefano Stabellini <stefano@...reto.com>
Subject: [PATCH 03/18] xen/pvcalls: initialize the module and register the xenbus backend

The pvcalls backend has one ioworker per cpu: the ioworkers are
implemented as a cpu bound workqueue, and will deal with the actual
socket and data ring reads/writes.

ioworkers are global: we only have one set for all the frontends. They
process requests on their wqs list in order, once they are done with a
request, they'll remove it from the list. A spinlock is used for
protecting the list. Each ioworker is bound to a different cpu to
maximize throughput.

Signed-off-by: Stefano Stabellini <stefano@...reto.com>
CC: boris.ostrovsky@...cle.com
CC: jgross@...e.com
---
 drivers/xen/pvcalls-back.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
index 2dbf7d8..46a889a 100644
--- a/drivers/xen/pvcalls-back.c
+++ b/drivers/xen/pvcalls-back.c
@@ -25,6 +25,26 @@
 #include <xen/xenbus.h>
 #include <xen/interface/io/pvcalls.h>
 
+struct pvcalls_ioworker {
+	struct work_struct register_work;
+	atomic_t io;
+	struct list_head wqs;
+	spinlock_t lock;
+	int num;
+};
+
+struct pvcalls_back_global {
+	struct pvcalls_ioworker *ioworkers;
+	int nr_ioworkers;
+	struct workqueue_struct *wq;
+	struct list_head privs;
+	struct rw_semaphore privs_lock;
+} pvcalls_back_global;
+
+static void pvcalls_back_ioworker(struct work_struct *work)
+{
+}
+
 static int pvcalls_back_probe(struct xenbus_device *dev,
 			      const struct xenbus_device_id *id)
 {
@@ -59,3 +79,47 @@ static int pvcalls_back_uevent(struct xenbus_device *xdev,
 	.uevent = pvcalls_back_uevent,
 	.otherend_changed = pvcalls_back_changed,
 };
+
+static int __init pvcalls_back_init(void)
+{
+	int ret, i, cpu;
+
+	if (!xen_domain())
+		return -ENODEV;
+
+	ret = xenbus_register_backend(&pvcalls_back_driver);
+	if (ret < 0)
+		return ret;
+
+	init_rwsem(&pvcalls_back_global.privs_lock);
+	INIT_LIST_HEAD(&pvcalls_back_global.privs);
+	pvcalls_back_global.wq = alloc_workqueue("pvcalls_io", 0, 0);
+	if (!pvcalls_back_global.wq)
+		goto error;
+	pvcalls_back_global.nr_ioworkers = num_online_cpus();
+	pvcalls_back_global.ioworkers = kzalloc(
+		sizeof(*pvcalls_back_global.ioworkers) *
+		pvcalls_back_global.nr_ioworkers, GFP_KERNEL);
+	if (!pvcalls_back_global.ioworkers)
+		goto error;
+	i = 0;
+	for_each_online_cpu(cpu) {
+		pvcalls_back_global.ioworkers[i].num = i;
+		atomic_set(&pvcalls_back_global.ioworkers[i].io, 1);
+		spin_lock_init(&pvcalls_back_global.ioworkers[i].lock);
+		INIT_LIST_HEAD(&pvcalls_back_global.ioworkers[i].wqs);
+		INIT_WORK(&pvcalls_back_global.ioworkers[i].register_work,
+			pvcalls_back_ioworker);
+		i++;
+	}
+	return 0;
+
+error:
+	if (pvcalls_back_global.wq)
+		destroy_workqueue(pvcalls_back_global.wq);
+	xenbus_unregister_driver(&pvcalls_back_driver);
+	kfree(pvcalls_back_global.ioworkers);
+	memset(&pvcalls_back_global, 0, sizeof(pvcalls_back_global));
+	return -ENOMEM;
+}
+module_init(pvcalls_back_init);
-- 
1.9.1