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Commit 37b96a49 authored by Stephen Hemminger's avatar Stephen Hemminger Committed by Greg Kroah-Hartman
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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: default avatarStephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent cf21be91

Documentation/ABI/stable/sysfs-bus-vmbus

+7 −0
Original line number Diff line number Diff line
@@ -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

Documentation/driver-api/uio-howto.rst

+5 −0
Original line number Diff line number Diff line
@@ -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

===================

drivers/uio/uio_hv_generic.c

+89 −0
Original line number Diff line number Diff line
@@ -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);