Intel MIC Host Driver Changes for Virtio Devices.

This patch introduces the host "Virtio over PCIe" interface for
Intel MIC. It allows creating user space backends on the host and instantiating
virtio devices for them on the Intel MIC card. It uses the existing VRINGH
infrastructure in the kernel to access virtio rings from the host. A character
device per MIC is exposed with IOCTL, mmap and poll callbacks. This allows the
user space backend to:
(a) add/remove a virtio device via a device page.
(b) map (R/O) virtio rings and device page to user space.
(c) poll for availability of data.
(d) copy a descriptor or entire descriptor chain to/from the card.
(e) modify virtio configuration.
(f) handle virtio device reset.
The buffers are copied over using CPU copies for this initial patch
and host initiated MIC DMA support is planned for future patches.
The avail and desc virtio rings are in host memory and the used ring
is in card memory to maximize writes across PCIe for performance.

Co-author: Sudeep Dutt <sudeep.dutt@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Caz Yokoyama <Caz.Yokoyama@intel.com>
Signed-off-by: Dasaratharaman Chandramouli <dasaratharaman.chandramouli@intel.com>
Signed-off-by: Nikhil Rao <nikhil.rao@intel.com>
Signed-off-by: Harshavardhan R Kharche <harshavardhan.r.kharche@intel.com>
Signed-off-by: Sudeep Dutt <sudeep.dutt@intel.com>
Acked-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
Reviewed-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 221 insertions, 0 deletions

diff --git a/drivers/misc/mic/host/mic_fops.c b/drivers/misc/mic/host/mic_fops.c
new file mode 100644
index 000000000000..661469ad339d
--- /dev/null
+++ b/drivers/misc/mic/host/mic_fops.c
@@ -0,0 +1,221 @@
+/*
+ * Intel MIC Platform Software Stack (MPSS)
+ *
+ * Copyright(c) 2013 Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * The full GNU General Public License is included in this distribution in
+ * the file called "COPYING".
+ *
+ * Intel MIC Host driver.
+ *
+ */
+#include <linux/poll.h>
+
+#include <linux/mic_common.h>
+#include "../common/mic_device.h"
+#include "mic_device.h"
+#include "mic_fops.h"
+#include "mic_virtio.h"
+
+int mic_open(struct inode *inode, struct file *f)
+{
+        struct mic_vdev *mvdev;
+        struct mic_device *mdev = container_of(inode->i_cdev,
+                struct mic_device, cdev);
+
+        mvdev = kzalloc(sizeof(*mvdev), GFP_KERNEL);
+        if (!mvdev)
+                return -ENOMEM;
+
+        init_waitqueue_head(&mvdev->waitq);
+        INIT_LIST_HEAD(&mvdev->list);
+        mvdev->mdev = mdev;
+        mvdev->virtio_id = -1;
+
+        f->private_data = mvdev;
+        return 0;
+}
+
+int mic_release(struct inode *inode, struct file *f)
+{
+        struct mic_vdev *mvdev = (struct mic_vdev *)f->private_data;
+
+        if (-1 != mvdev->virtio_id)
+                mic_virtio_del_device(mvdev);
+        f->private_data = NULL;
+        kfree(mvdev);
+        return 0;
+}
+
+long mic_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
+{
+        struct mic_vdev *mvdev = (struct mic_vdev *)f->private_data;
+        void __user *argp = (void __user *)arg;
+        int ret;
+
+        switch (cmd) {
+        case MIC_VIRTIO_ADD_DEVICE:
+        {
+                ret = mic_virtio_add_device(mvdev, argp);
+                if (ret < 0) {
+                        dev_err(mic_dev(mvdev),
+                                "%s %d errno ret %d\n",
+                                __func__, __LINE__, ret);
+                        return ret;
+                }
+                break;
+        }
+        case MIC_VIRTIO_COPY_DESC:
+        {
+                struct mic_copy_desc copy;
+
+                ret = mic_vdev_inited(mvdev);
+                if (ret)
+                        return ret;
+
+                if (copy_from_user(&copy, argp, sizeof(copy)))
+                        return -EFAULT;
+
+                dev_dbg(mic_dev(mvdev),
+                        "%s %d === iovcnt 0x%x vr_idx 0x%x update_used %d\n",
+                        __func__, __LINE__, copy.iovcnt, copy.vr_idx,
+                        copy.update_used);
+
+                ret = mic_virtio_copy_desc(mvdev, &copy);
+                if (ret < 0) {
+                        dev_err(mic_dev(mvdev),
+                                "%s %d errno ret %d\n",
+                                __func__, __LINE__, ret);
+                        return ret;
+                }
+                if (copy_to_user(
+                        &((struct mic_copy_desc __user *)argp)->out_len,
+                        &copy.out_len, sizeof(copy.out_len))) {
+                        dev_err(mic_dev(mvdev), "%s %d errno ret %d\n",
+                                __func__, __LINE__, -EFAULT);
+                        return -EFAULT;
+                }
+                break;
+        }
+        case MIC_VIRTIO_CONFIG_CHANGE:
+        {
+                ret = mic_vdev_inited(mvdev);
+                if (ret)
+                        return ret;
+
+                ret = mic_virtio_config_change(mvdev, argp);
+                if (ret < 0) {
+                        dev_err(mic_dev(mvdev),
+                                "%s %d errno ret %d\n",
+                                __func__, __LINE__, ret);
+                        return ret;
+                }
+                break;
+        }
+        default:
+                return -ENOIOCTLCMD;
+        };
+        return 0;
+}
+
+/*
+ * We return POLLIN | POLLOUT from poll when new buffers are enqueued, and
+ * not when previously enqueued buffers may be available. This means that
+ * in the card->host (TX) path, when userspace is unblocked by poll it
+ * must drain all available descriptors or it can stall.
+ */
+unsigned int mic_poll(struct file *f, poll_table *wait)
+{
+        struct mic_vdev *mvdev = (struct mic_vdev *)f->private_data;
+        int mask = 0;
+
+        poll_wait(f, &mvdev->waitq, wait);
+
+        if (mic_vdev_inited(mvdev))
+                mask = POLLERR;
+        else if (mvdev->poll_wake) {
+                mvdev->poll_wake = 0;
+                mask = POLLIN | POLLOUT;
+        }
+
+        return mask;
+}
+
+static inline int
+mic_query_offset(struct mic_vdev *mvdev, unsigned long offset,
+        unsigned long *size, unsigned long *pa)
+{
+        struct mic_device *mdev = mvdev->mdev;
+        unsigned long start = MIC_DP_SIZE;
+        int i;
+
+        /*
+         * MMAP interface is as follows:
+         * offset                               region
+         * 0x0                                  virtio device_page
+         * 0x1000                               first vring
+         * 0x1000 + size of 1st vring           second vring
+         * ....
+         */
+        if (!offset) {
+                *pa = virt_to_phys(mdev->dp);
+                *size = MIC_DP_SIZE;
+                return 0;
+        }
+
+        for (i = 0; i < mvdev->dd->num_vq; i++) {
+                struct mic_vringh *mvr = &mvdev->mvr[i];
+                if (offset == start) {
+                        *pa = virt_to_phys(mvr->vring.va);
+                        *size = mvr->vring.len;
+                        return 0;
+                }
+                start += mvr->vring.len;
+        }
+        return -1;
+}
+
+/*
+ * Maps the device page and virtio rings to user space for readonly access.
+ */
+int
+mic_mmap(struct file *f, struct vm_area_struct *vma)
+{
+        struct mic_vdev *mvdev = (struct mic_vdev *)f->private_data;
+        unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
+        unsigned long pa, size = vma->vm_end - vma->vm_start, size_rem = size;
+        int i, err;
+
+        err = mic_vdev_inited(mvdev);
+        if (err)
+                return err;
+
+        if (vma->vm_flags & VM_WRITE)
+                return -EACCES;
+
+        while (size_rem) {
+                i = mic_query_offset(mvdev, offset, &size, &pa);
+                if (i < 0)
+                        return -EINVAL;
+                err = remap_pfn_range(vma, vma->vm_start + offset,
+                        pa >> PAGE_SHIFT, size, vma->vm_page_prot);
+                if (err)
+                        return err;
+                dev_dbg(mic_dev(mvdev),
+                        "%s %d type %d size 0x%lx off 0x%lx pa 0x%lx vma 0x%lx\n",
+                        __func__, __LINE__, mvdev->virtio_id, size, offset,
+                        pa, vma->vm_start + offset);
+                size_rem -= size;
+                offset += size;
+        }
+        return 0;
+}