uio_hv_generic: support sub-channels

Use sysfs to allow supporting sub-channels. The userspace application
makes request to host to create sub-channels and the UIO kernel
driver populates the sysfs per-channel directory with a binary
attribute file that can be used to read/write ring.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/ABI/stable/sysfs-bus-vmbus b/Documentation/ABI/stable/sysfs-bus-vmbus
index e46be65d0e1d2fd3525111f8670d79d37dc39e53..0c9d9dcd2151d183e46c2f37a4392061424ca76b 100644 (file)
--- a/Documentation/ABI/stable/sysfs-bus-vmbus
+++ b/Documentation/ABI/stable/sysfs-bus-vmbus
@@ -132,3 +132,10 @@ KernelVersion:     4.16
 Contact:       Stephen Hemminger <sthemmin@microsoft.com>
 Description:   Monitor bit associated with channel
 Users:         Debugging tools and userspace drivers
+
+What:          /sys/bus/vmbus/devices/vmbus_*/channels/NN/ring
+Date:          January. 2018
+KernelVersion: 4.16
+Contact:       Stephen Hemminger <sthemmin@microsoft.com>
+Description:   Binary file created by uio_hv_generic for ring buffer
+Users:         Userspace drivers

diff --git a/Documentation/driver-api/uio-howto.rst b/Documentation/driver-api/uio-howto.rst
index 693e3bd84e79ae48df6519f03b7de330c488b038..92056c20e070649debad6b84b4442413c1611678 100644 (file)
--- a/Documentation/driver-api/uio-howto.rst
+++ b/Documentation/driver-api/uio-howto.rst
@@ -709,6 +709,11 @@ The vmbus device regions are mapped into uio device resources:
     3) Network receive buffer region
     4) Network send buffer region
 
+If a subchannel is created by a request to host, then the uio_hv_generic
+device driver will create a sysfs binary file for the per-channel ring buffer.
+For example:
+       /sys/bus/vmbus/devices/3811fe4d-0fa0-4b62-981a-74fc1084c757/channels/21/ring
+
 Further information
 ===================
 

diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
index 8ca549032c27342ff01c219ee298d1d1d0c613fb..f695a7e8c314585c8b0df8ab88f44d897986839b 100644 (file)
--- a/drivers/uio/uio_hv_generic.c
+++ b/drivers/uio/uio_hv_generic.c
@@ -121,6 +121,94 @@ static void hv_uio_rescind(struct vmbus_channel *channel)
        uio_event_notify(&pdata->info);
 }
 
+/*
+ * Handle fault when looking for sub channel ring buffer
+ * Subchannel ring buffer is same as resource 0 which is main ring buffer
+ * This is derived from uio_vma_fault
+ */
+static int hv_uio_vma_fault(struct vm_fault *vmf)
+{
+       struct vm_area_struct *vma = vmf->vma;
+       void *ring_buffer = vma->vm_private_data;
+       struct page *page;
+       void *addr;
+
+       addr = ring_buffer + (vmf->pgoff << PAGE_SHIFT);
+       page = virt_to_page(addr);
+       get_page(page);
+       vmf->page = page;
+       return 0;
+}
+
+static const struct vm_operations_struct hv_uio_vm_ops = {
+       .fault = hv_uio_vma_fault,
+};
+
+/* Sysfs API to allow mmap of the ring buffers */
+static int hv_uio_ring_mmap(struct file *filp, struct kobject *kobj,
+                           struct bin_attribute *attr,
+                           struct vm_area_struct *vma)
+{
+       struct vmbus_channel *channel
+               = container_of(kobj, struct vmbus_channel, kobj);
+       unsigned long requested_pages, actual_pages;
+
+       if (vma->vm_end < vma->vm_start)
+               return -EINVAL;
+
+       /* only allow 0 for now */
+       if (vma->vm_pgoff > 0)
+               return -EINVAL;
+
+       requested_pages = vma_pages(vma);
+       actual_pages = 2 * HV_RING_SIZE;
+       if (requested_pages > actual_pages)
+               return -EINVAL;
+
+       vma->vm_private_data = channel->ringbuffer_pages;
+       vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
+       vma->vm_ops = &hv_uio_vm_ops;
+       return 0;
+}
+
+static struct bin_attribute ring_buffer_bin_attr __ro_after_init = {
+       .attr = {
+               .name = "ring",
+               .mode = 0600,
+               /* size is set at init time */
+       },
+       .mmap = hv_uio_ring_mmap,
+};
+
+/* Callback from VMBUS subystem when new channel created. */
+static void
+hv_uio_new_channel(struct vmbus_channel *new_sc)
+{
+       struct hv_device *hv_dev = new_sc->primary_channel->device_obj;
+       struct device *device = &hv_dev->device;
+       struct hv_uio_private_data *pdata = hv_get_drvdata(hv_dev);
+       const size_t ring_bytes = HV_RING_SIZE * PAGE_SIZE;
+       int ret;
+
+       /* Create host communication ring */
+       ret = vmbus_open(new_sc, ring_bytes, ring_bytes, NULL, 0,
+                        hv_uio_channel_cb, pdata);
+       if (ret) {
+               dev_err(device, "vmbus_open subchannel failed: %d\n", ret);
+               return;
+       }
+
+       /* Disable interrupts on sub channel */
+       new_sc->inbound.ring_buffer->interrupt_mask = 1;
+       set_channel_read_mode(new_sc, HV_CALL_ISR);
+
+       ret = sysfs_create_bin_file(&new_sc->kobj, &ring_buffer_bin_attr);
+       if (ret) {
+               dev_err(device, "sysfs create ring bin file failed; %d\n", ret);
+               vmbus_close(new_sc);
+       }
+}
+
 static void
 hv_uio_cleanup(struct hv_device *dev, struct hv_uio_private_data *pdata)
 {
@@ -236,6 +324,7 @@ hv_uio_probe(struct hv_device *dev,
        }
 
        vmbus_set_chn_rescind_callback(dev->channel, hv_uio_rescind);
+       vmbus_set_sc_create_callback(dev->channel, hv_uio_new_channel);
 
        hv_set_drvdata(dev, pdata);