IB/ipath: Performance improvements via mmap of queues

Improve performance of userspace post receive, post SRQ receive, and
poll CQ operations for ipath by allowing userspace to directly mmap()
receive queues and completion queues.  This eliminates the copying
between userspace and the kernel in the data path.

Signed-off-by: Ralph Campbell <ralph.campbell@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 122 insertions, 0 deletions

diff --git a/drivers/infiniband/hw/ipath/ipath_mmap.c b/drivers/infiniband/hw/ipath/ipath_mmap.c
new file mode 100644
index 000000000000..11b7378ff214
--- /dev/null
+++ b/drivers/infiniband/hw/ipath/ipath_mmap.c
@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2006 QLogic, Inc. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *      - Redistributions of source code must retain the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer.
+ *
+ *      - Redistributions in binary form must reproduce the above
+ *        copyright notice, this list of conditions and the following
+ *        disclaimer in the documentation and/or other materials
+ *        provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/vmalloc.h>
+#include <linux/mm.h>
+#include <linux/errno.h>
+#include <asm/pgtable.h>
+
+#include "ipath_verbs.h"
+
+/**
+ * ipath_release_mmap_info - free mmap info structure
+ * @ref: a pointer to the kref within struct ipath_mmap_info
+ */
+void ipath_release_mmap_info(struct kref *ref)
+{
+	struct ipath_mmap_info *ip =
+		container_of(ref, struct ipath_mmap_info, ref);
+
+	vfree(ip->obj);
+	kfree(ip);
+}
+
+/*
+ * open and close keep track of how many times the CQ is mapped,
+ * to avoid releasing it.
+ */
+static void ipath_vma_open(struct vm_area_struct *vma)
+{
+	struct ipath_mmap_info *ip = vma->vm_private_data;
+
+	kref_get(&ip->ref);
+	ip->mmap_cnt++;
+}
+
+static void ipath_vma_close(struct vm_area_struct *vma)
+{
+	struct ipath_mmap_info *ip = vma->vm_private_data;
+
+	ip->mmap_cnt--;
+	kref_put(&ip->ref, ipath_release_mmap_info);
+}
+
+static struct vm_operations_struct ipath_vm_ops = {
+	.open =     ipath_vma_open,
+	.close =    ipath_vma_close,
+};
+
+/**
+ * ipath_mmap - create a new mmap region
+ * @context: the IB user context of the process making the mmap() call
+ * @vma: the VMA to be initialized
+ * Return zero if the mmap is OK. Otherwise, return an errno.
+ */
+int ipath_mmap(struct ib_ucontext *context, struct vm_area_struct *vma)
+{
+	struct ipath_ibdev *dev = to_idev(context->device);
+	unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
+	unsigned long size = vma->vm_end - vma->vm_start;
+	struct ipath_mmap_info *ip, **pp;
+	int ret = -EINVAL;
+
+	/*
+	 * Search the device's list of objects waiting for a mmap call.
+	 * Normally, this list is very short since a call to create a
+	 * CQ, QP, or SRQ is soon followed by a call to mmap().
+	 */
+	spin_lock_irq(&dev->pending_lock);
+	for (pp = &dev->pending_mmaps; (ip = *pp); pp = &ip->next) {
+		/* Only the creator is allowed to mmap the object */
+		if (context != ip->context || (void *) offset != ip->obj)
+			continue;
+		/* Don't allow a mmap larger than the object. */
+		if (size > ip->size)
+			break;
+
+		*pp = ip->next;
+		spin_unlock_irq(&dev->pending_lock);
+
+		ret = remap_vmalloc_range(vma, ip->obj, 0);
+		if (ret)
+			goto done;
+		vma->vm_ops = &ipath_vm_ops;
+		vma->vm_private_data = ip;
+		ipath_vma_open(vma);
+		goto done;
+	}
+	spin_unlock_irq(&dev->pending_lock);
+done:
+	return ret;
+}