![Rusty Russell](/assets/img/avatar_default.png)
This API change means that virtio_net can tell how much capacity remains for buffers. It's necessarily fuzzy, since VIRTIO_RING_F_INDIRECT_DESC means we can fit any number of descriptors in one, *if* we can kmalloc. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Dinesh Subhraveti <dineshs@us.ibm.com>
438 lines
11 KiB
C
438 lines
11 KiB
C
/* Virtio ring implementation.
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*
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* Copyright 2007 Rusty Russell IBM Corporation
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <linux/virtio.h>
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#include <linux/virtio_ring.h>
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#include <linux/virtio_config.h>
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#include <linux/device.h>
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#ifdef DEBUG
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/* For development, we want to crash whenever the ring is screwed. */
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#define BAD_RING(_vq, fmt, args...) \
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do { \
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dev_err(&(_vq)->vq.vdev->dev, \
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"%s:"fmt, (_vq)->vq.name, ##args); \
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BUG(); \
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} while (0)
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/* Caller is supposed to guarantee no reentry. */
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#define START_USE(_vq) \
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do { \
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if ((_vq)->in_use) \
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panic("%s:in_use = %i\n", \
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(_vq)->vq.name, (_vq)->in_use); \
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(_vq)->in_use = __LINE__; \
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mb(); \
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} while (0)
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#define END_USE(_vq) \
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do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; mb(); } while(0)
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#else
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#define BAD_RING(_vq, fmt, args...) \
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do { \
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dev_err(&_vq->vq.vdev->dev, \
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"%s:"fmt, (_vq)->vq.name, ##args); \
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(_vq)->broken = true; \
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} while (0)
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#define START_USE(vq)
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#define END_USE(vq)
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#endif
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struct vring_virtqueue
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{
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struct virtqueue vq;
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/* Actual memory layout for this queue */
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struct vring vring;
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/* Other side has made a mess, don't try any more. */
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bool broken;
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/* Host supports indirect buffers */
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bool indirect;
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/* Number of free buffers */
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unsigned int num_free;
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/* Head of free buffer list. */
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unsigned int free_head;
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/* Number we've added since last sync. */
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unsigned int num_added;
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/* Last used index we've seen. */
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u16 last_used_idx;
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/* How to notify other side. FIXME: commonalize hcalls! */
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void (*notify)(struct virtqueue *vq);
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#ifdef DEBUG
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/* They're supposed to lock for us. */
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unsigned int in_use;
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#endif
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/* Tokens for callbacks. */
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void *data[];
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};
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#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
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/* Set up an indirect table of descriptors and add it to the queue. */
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static int vring_add_indirect(struct vring_virtqueue *vq,
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struct scatterlist sg[],
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unsigned int out,
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unsigned int in)
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{
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struct vring_desc *desc;
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unsigned head;
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int i;
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desc = kmalloc((out + in) * sizeof(struct vring_desc), GFP_ATOMIC);
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if (!desc)
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return vq->vring.num;
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/* Transfer entries from the sg list into the indirect page */
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for (i = 0; i < out; i++) {
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desc[i].flags = VRING_DESC_F_NEXT;
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desc[i].addr = sg_phys(sg);
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desc[i].len = sg->length;
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desc[i].next = i+1;
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sg++;
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}
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for (; i < (out + in); i++) {
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desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
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desc[i].addr = sg_phys(sg);
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desc[i].len = sg->length;
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desc[i].next = i+1;
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sg++;
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}
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/* Last one doesn't continue. */
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desc[i-1].flags &= ~VRING_DESC_F_NEXT;
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desc[i-1].next = 0;
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/* We're about to use a buffer */
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vq->num_free--;
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/* Use a single buffer which doesn't continue */
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head = vq->free_head;
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vq->vring.desc[head].flags = VRING_DESC_F_INDIRECT;
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vq->vring.desc[head].addr = virt_to_phys(desc);
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vq->vring.desc[head].len = i * sizeof(struct vring_desc);
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/* Update free pointer */
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vq->free_head = vq->vring.desc[head].next;
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return head;
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}
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static int vring_add_buf(struct virtqueue *_vq,
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struct scatterlist sg[],
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unsigned int out,
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unsigned int in,
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void *data)
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{
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struct vring_virtqueue *vq = to_vvq(_vq);
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unsigned int i, avail, head, uninitialized_var(prev);
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START_USE(vq);
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BUG_ON(data == NULL);
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/* If the host supports indirect descriptor tables, and we have multiple
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* buffers, then go indirect. FIXME: tune this threshold */
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if (vq->indirect && (out + in) > 1 && vq->num_free) {
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head = vring_add_indirect(vq, sg, out, in);
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if (head != vq->vring.num)
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goto add_head;
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}
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BUG_ON(out + in > vq->vring.num);
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BUG_ON(out + in == 0);
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if (vq->num_free < out + in) {
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pr_debug("Can't add buf len %i - avail = %i\n",
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out + in, vq->num_free);
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/* FIXME: for historical reasons, we force a notify here if
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* there are outgoing parts to the buffer. Presumably the
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* host should service the ring ASAP. */
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if (out)
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vq->notify(&vq->vq);
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END_USE(vq);
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return -ENOSPC;
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}
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/* We're about to use some buffers from the free list. */
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vq->num_free -= out + in;
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head = vq->free_head;
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for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) {
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vq->vring.desc[i].flags = VRING_DESC_F_NEXT;
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vq->vring.desc[i].addr = sg_phys(sg);
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vq->vring.desc[i].len = sg->length;
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prev = i;
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sg++;
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}
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for (; in; i = vq->vring.desc[i].next, in--) {
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vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
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vq->vring.desc[i].addr = sg_phys(sg);
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vq->vring.desc[i].len = sg->length;
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prev = i;
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sg++;
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}
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/* Last one doesn't continue. */
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vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT;
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/* Update free pointer */
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vq->free_head = i;
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add_head:
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/* Set token. */
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vq->data[head] = data;
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/* Put entry in available array (but don't update avail->idx until they
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* do sync). FIXME: avoid modulus here? */
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avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num;
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vq->vring.avail->ring[avail] = head;
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pr_debug("Added buffer head %i to %p\n", head, vq);
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END_USE(vq);
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/* If we're indirect, we can fit many (assuming not OOM). */
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if (vq->indirect)
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return vq->num_free ? vq->vring.num : 0;
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return vq->num_free;
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}
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static void vring_kick(struct virtqueue *_vq)
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{
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struct vring_virtqueue *vq = to_vvq(_vq);
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START_USE(vq);
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/* Descriptors and available array need to be set before we expose the
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* new available array entries. */
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wmb();
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vq->vring.avail->idx += vq->num_added;
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vq->num_added = 0;
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/* Need to update avail index before checking if we should notify */
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mb();
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if (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
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/* Prod other side to tell it about changes. */
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vq->notify(&vq->vq);
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END_USE(vq);
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}
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static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
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{
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unsigned int i;
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/* Clear data ptr. */
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vq->data[head] = NULL;
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/* Put back on free list: find end */
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i = head;
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/* Free the indirect table */
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if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT)
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kfree(phys_to_virt(vq->vring.desc[i].addr));
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while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
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i = vq->vring.desc[i].next;
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vq->num_free++;
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}
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vq->vring.desc[i].next = vq->free_head;
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vq->free_head = head;
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/* Plus final descriptor */
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vq->num_free++;
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}
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static inline bool more_used(const struct vring_virtqueue *vq)
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{
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return vq->last_used_idx != vq->vring.used->idx;
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}
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static void *vring_get_buf(struct virtqueue *_vq, unsigned int *len)
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{
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struct vring_virtqueue *vq = to_vvq(_vq);
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void *ret;
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unsigned int i;
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START_USE(vq);
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if (unlikely(vq->broken)) {
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END_USE(vq);
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return NULL;
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}
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if (!more_used(vq)) {
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pr_debug("No more buffers in queue\n");
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END_USE(vq);
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return NULL;
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}
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i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
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*len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;
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if (unlikely(i >= vq->vring.num)) {
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BAD_RING(vq, "id %u out of range\n", i);
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return NULL;
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}
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if (unlikely(!vq->data[i])) {
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BAD_RING(vq, "id %u is not a head!\n", i);
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return NULL;
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}
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/* detach_buf clears data, so grab it now. */
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ret = vq->data[i];
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detach_buf(vq, i);
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vq->last_used_idx++;
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END_USE(vq);
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return ret;
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}
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static void vring_disable_cb(struct virtqueue *_vq)
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{
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struct vring_virtqueue *vq = to_vvq(_vq);
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vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
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}
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static bool vring_enable_cb(struct virtqueue *_vq)
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{
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struct vring_virtqueue *vq = to_vvq(_vq);
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START_USE(vq);
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/* We optimistically turn back on interrupts, then check if there was
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* more to do. */
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vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
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mb();
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if (unlikely(more_used(vq))) {
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END_USE(vq);
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return false;
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}
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END_USE(vq);
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return true;
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}
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irqreturn_t vring_interrupt(int irq, void *_vq)
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{
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struct vring_virtqueue *vq = to_vvq(_vq);
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if (!more_used(vq)) {
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pr_debug("virtqueue interrupt with no work for %p\n", vq);
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return IRQ_NONE;
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}
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if (unlikely(vq->broken))
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return IRQ_HANDLED;
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pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
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if (vq->vq.callback)
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vq->vq.callback(&vq->vq);
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return IRQ_HANDLED;
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}
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EXPORT_SYMBOL_GPL(vring_interrupt);
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static struct virtqueue_ops vring_vq_ops = {
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.add_buf = vring_add_buf,
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.get_buf = vring_get_buf,
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.kick = vring_kick,
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.disable_cb = vring_disable_cb,
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.enable_cb = vring_enable_cb,
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};
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struct virtqueue *vring_new_virtqueue(unsigned int num,
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unsigned int vring_align,
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struct virtio_device *vdev,
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void *pages,
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void (*notify)(struct virtqueue *),
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void (*callback)(struct virtqueue *),
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const char *name)
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{
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struct vring_virtqueue *vq;
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unsigned int i;
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/* We assume num is a power of 2. */
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if (num & (num - 1)) {
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dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
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return NULL;
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}
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vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL);
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if (!vq)
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return NULL;
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vring_init(&vq->vring, num, pages, vring_align);
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vq->vq.callback = callback;
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vq->vq.vdev = vdev;
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vq->vq.vq_ops = &vring_vq_ops;
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vq->vq.name = name;
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vq->notify = notify;
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vq->broken = false;
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vq->last_used_idx = 0;
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vq->num_added = 0;
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list_add_tail(&vq->vq.list, &vdev->vqs);
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#ifdef DEBUG
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vq->in_use = false;
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#endif
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vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
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/* No callback? Tell other side not to bother us. */
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if (!callback)
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vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
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/* Put everything in free lists. */
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vq->num_free = num;
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vq->free_head = 0;
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for (i = 0; i < num-1; i++)
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vq->vring.desc[i].next = i+1;
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return &vq->vq;
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}
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EXPORT_SYMBOL_GPL(vring_new_virtqueue);
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void vring_del_virtqueue(struct virtqueue *vq)
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{
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list_del(&vq->list);
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kfree(to_vvq(vq));
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}
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EXPORT_SYMBOL_GPL(vring_del_virtqueue);
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/* Manipulates transport-specific feature bits. */
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void vring_transport_features(struct virtio_device *vdev)
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{
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unsigned int i;
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for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
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switch (i) {
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case VIRTIO_RING_F_INDIRECT_DESC:
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break;
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default:
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/* We don't understand this bit. */
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clear_bit(i, vdev->features);
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}
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}
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}
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EXPORT_SYMBOL_GPL(vring_transport_features);
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MODULE_LICENSE("GPL");
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