2007-10-22 08:03:36 +07:00
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#ifndef _LINUX_VIRTIO_H
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#define _LINUX_VIRTIO_H
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/* Everything a virtio driver needs to work with any particular virtio
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* implementation. */
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#include <linux/types.h>
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#include <linux/scatterlist.h>
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#include <linux/spinlock.h>
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#include <linux/device.h>
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#include <linux/mod_devicetable.h>
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2010-04-29 21:26:37 +07:00
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#include <linux/gfp.h>
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2007-10-22 08:03:36 +07:00
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/**
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* virtqueue - a queue to register buffers for sending or receiving.
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2009-06-13 11:16:35 +07:00
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* @list: the chain of virtqueues for this device
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2007-10-22 08:03:36 +07:00
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* @callback: the function to call when buffers are consumed (can be NULL).
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2009-06-13 11:16:35 +07:00
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* @name: the name of this virtqueue (mainly for debugging)
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* @vdev: the virtio device this queue was created for.
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* @priv: a pointer for the virtqueue implementation to use.
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*/
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struct virtqueue {
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struct list_head list;
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void (*callback)(struct virtqueue *vq);
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const char *name;
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struct virtio_device *vdev;
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void *priv;
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};
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/**
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* operations for virtqueue
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* virtqueue_add_buf: expose buffer to other end
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2007-10-22 08:03:36 +07:00
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* vq: the struct virtqueue we're talking about.
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* sg: the description of the buffer(s).
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* out_num: the number of sg readable by other side
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* in_num: the number of sg which are writable (after readable ones)
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* data: the token identifying the buffer.
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* gfp: how to do memory allocations (if necessary).
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* Returns remaining capacity of queue (sg segments) or a negative error.
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* virtqueue_kick: update after add_buf
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* vq: the struct virtqueue
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* After one or more add_buf calls, invoke this to kick the other side.
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* virtqueue_get_buf: get the next used buffer
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* vq: the struct virtqueue we're talking about.
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* len: the length written into the buffer
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* Returns NULL or the "data" token handed to add_buf.
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* virtqueue_disable_cb: disable callbacks
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* vq: the struct virtqueue we're talking about.
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2008-04-07 11:30:28 +07:00
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* Note that this is not necessarily synchronous, hence unreliable and only
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* useful as an optimization.
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2010-04-12 20:19:07 +07:00
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* virtqueue_enable_cb: restart callbacks after disable_cb.
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2007-10-22 08:03:36 +07:00
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* vq: the struct virtqueue we're talking about.
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virtio: fix race in enable_cb
There is a race in virtio_net, dealing with disabling/enabling the callback.
I saw the following oops:
kernel BUG at /space/kvm/drivers/virtio/virtio_ring.c:218!
illegal operation: 0001 [#1] SMP
Modules linked in: sunrpc dm_mod
CPU: 2 Not tainted 2.6.25-rc1zlive-host-10623-gd358142-dirty #99
Process swapper (pid: 0, task: 000000000f85a610, ksp: 000000000f873c60)
Krnl PSW : 0404300180000000 00000000002b81a6 (vring_disable_cb+0x16/0x20)
R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:0 CC:3 PM:0 EA:3
Krnl GPRS: 0000000000000001 0000000000000001 0000000010005800 0000000000000001
000000000f3a0900 000000000f85a610 0000000000000000 0000000000000000
0000000000000000 000000000f870000 0000000000000000 0000000000001237
000000000f3a0920 000000000010ff74 00000000002846f6 000000000fa0bcd8
Krnl Code: 00000000002b819a: a7110001 tmll %r1,1
00000000002b819e: a7840004 brc 8,2b81a6
00000000002b81a2: a7f40001 brc 15,2b81a4
>00000000002b81a6: a51b0001 oill %r1,1
00000000002b81aa: 40102000 sth %r1,0(%r2)
00000000002b81ae: 07fe bcr 15,%r14
00000000002b81b0: eb7ff0380024 stmg %r7,%r15,56(%r15)
00000000002b81b6: a7f13e00 tmll %r15,15872
Call Trace:
([<000000000fa0bcd0>] 0xfa0bcd0)
[<00000000002b8350>] vring_interrupt+0x5c/0x6c
[<000000000010ab08>] do_extint+0xb8/0xf0
[<0000000000110716>] ext_no_vtime+0x16/0x1a
[<0000000000107e72>] cpu_idle+0x1c2/0x1e0
The problem can be triggered with a high amount of host->guest traffic.
I think its the following race:
poll says netif_rx_complete
poll calls enable_cb
enable_cb opens the interrupt mask
a new packet comes, an interrupt is triggered----\
enable_cb sees that there is more work |
enable_cb disables the interrupt |
. V
. interrupt is delivered
. skb_recv_done does atomic napi test, ok
some waiting disable_cb is called->check fails->bang!
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poll would do napi check
poll would do disable_cb
The fix is to let enable_cb not disable the interrupt again, but expect the
caller to do the cleanup if it returns false. In that case, the interrupt is
only disabled, if the napi test_set_bit was successful.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (cleaned up doco)
2008-03-14 20:17:05 +07:00
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* This re-enables callbacks; it returns "false" if there are pending
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* buffers in the queue, to detect a possible race between the driver
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* checking for more work, and enabling callbacks.
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2011-05-20 06:11:14 +07:00
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* virtqueue_enable_cb_delayed: restart callbacks after disable_cb.
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* vq: the struct virtqueue we're talking about.
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* This re-enables callbacks but hints to the other side to delay
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* interrupts until most of the available buffers have been processed;
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* it returns "false" if there are many pending buffers in the queue,
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* to detect a possible race between the driver checking for more work,
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* and enabling callbacks.
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2010-04-12 20:19:07 +07:00
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* virtqueue_detach_unused_buf: detach first unused buffer
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2010-01-18 20:45:23 +07:00
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* vq: the struct virtqueue we're talking about.
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* Returns NULL or the "data" token handed to add_buf
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2011-10-19 15:10:59 +07:00
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* virtqueue_get_vring_size: return the size of the virtqueue's vring
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* vq: the struct virtqueue containing the vring of interest.
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* Returns the size of the vring.
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*
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* Locking rules are straightforward: the driver is responsible for
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* locking. No two operations may be invoked simultaneously, with the exception
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* of virtqueue_disable_cb.
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*
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* All operations can be called in any context.
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*/
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2010-04-29 21:26:37 +07:00
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int virtqueue_add_buf_gfp(struct virtqueue *vq,
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struct scatterlist sg[],
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unsigned int out_num,
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unsigned int in_num,
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void *data,
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gfp_t gfp);
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static inline int virtqueue_add_buf(struct virtqueue *vq,
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struct scatterlist sg[],
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unsigned int out_num,
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unsigned int in_num,
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void *data)
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{
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return virtqueue_add_buf_gfp(vq, sg, out_num, in_num, data, GFP_ATOMIC);
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}
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void virtqueue_kick(struct virtqueue *vq);
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void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len);
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void virtqueue_disable_cb(struct virtqueue *vq);
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bool virtqueue_enable_cb(struct virtqueue *vq);
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2010-04-12 20:18:25 +07:00
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2011-05-20 06:11:14 +07:00
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bool virtqueue_enable_cb_delayed(struct virtqueue *vq);
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2010-04-12 20:19:07 +07:00
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void *virtqueue_detach_unused_buf(struct virtqueue *vq);
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2010-04-12 20:18:25 +07:00
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2011-10-19 15:10:59 +07:00
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unsigned int virtqueue_get_vring_size(struct virtqueue *vq);
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2007-10-22 08:03:36 +07:00
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/**
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* virtio_device - representation of a device using virtio
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* @index: unique position on the virtio bus
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* @dev: underlying device.
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* @id: the device type identification (used to match it with a driver).
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* @config: the configuration ops for this device.
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* @vqs: the list of virtqueues for this device.
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2008-05-03 09:50:50 +07:00
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* @features: the features supported by both driver and device.
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* @priv: private pointer for the driver's use.
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*/
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struct virtio_device {
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int index;
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struct device dev;
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struct virtio_device_id id;
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struct virtio_config_ops *config;
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struct list_head vqs;
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/* Note that this is a Linux set_bit-style bitmap. */
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unsigned long features[1];
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void *priv;
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};
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2010-03-06 11:44:15 +07:00
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#define dev_to_virtio(dev) container_of(dev, struct virtio_device, dev)
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int register_virtio_device(struct virtio_device *dev);
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void unregister_virtio_device(struct virtio_device *dev);
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/**
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* virtio_driver - operations for a virtio I/O driver
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* @driver: underlying device driver (populate name and owner).
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* @id_table: the ids serviced by this driver.
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* @feature_table: an array of feature numbers supported by this driver.
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* @feature_table_size: number of entries in the feature table array.
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2009-06-13 11:16:33 +07:00
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* @probe: the function to call when a device is found. Returns 0 or -errno.
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* @remove: the function to call when a device is removed.
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* @config_changed: optional function to call when the device configuration
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* changes; may be called in interrupt context.
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*/
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struct virtio_driver {
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struct device_driver driver;
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const struct virtio_device_id *id_table;
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const unsigned int *feature_table;
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unsigned int feature_table_size;
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int (*probe)(struct virtio_device *dev);
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void (*remove)(struct virtio_device *dev);
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void (*config_changed)(struct virtio_device *dev);
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};
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int register_virtio_driver(struct virtio_driver *drv);
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void unregister_virtio_driver(struct virtio_driver *drv);
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#endif /* _LINUX_VIRTIO_H */
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