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@xxxxxxxxxxxxx>
---
Documentation/driver-api/uio-howto.rst | 5 ++
drivers/uio/uio_hv_generic.c | 91 ++++++++++++++++++++++++++++++++++
2 files changed, 96 insertions(+)
diff --git a/Documentation/driver-api/uio-howto.rst b/Documentation/driver-api/uio-howto.rst
index 0030de9205fd..23509429c85c 100644
--- 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_buffer
+
Further information
===================
diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
index eab173665dd4..a2289122e99d 100644
--- a/drivers/uio/uio_hv_generic.c
+++ b/drivers/uio/uio_hv_generic.c
@@ -133,6 +133,94 @@ 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 * 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);
+ int ret;
+
+ /* Create host communication ring */
+ ret = vmbus_open(new_sc, ring_size * PAGE_SIZE,
+ ring_size * PAGE_SIZE, 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)
{
@@ -266,6 +354,7 @@ 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);
@@ -319,6 +408,8 @@ hyperv_module_init(void)
ring_size);
}
+ ring_buffer_bin_attr.size = 2 * ring_size * PAGE_SIZE;
+
if (recv_buffer_size > RECV_BUFFER_MAX) {
recv_buffer_size = RECV_BUFFER_MAX;
pr_info("Decreased receive_buffer_size to %u (max allowed)\n",
--
2.15.1
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