![Rusty Russell](/assets/img/avatar_default.png)
Now noone relies on this behavior, we simplify virtqueue_add_buf() so it return 0 or -errno. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Acked-by: Michael S. Tsirkin <mst@redhat.com>
723 lines
19 KiB
C
723 lines
19 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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#include <linux/slab.h>
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#include <linux/module.h>
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#include <linux/hrtimer.h>
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/* virtio guest is communicating with a virtual "device" that actually runs on
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* a host processor. Memory barriers are used to control SMP effects. */
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#ifdef CONFIG_SMP
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/* Where possible, use SMP barriers which are more lightweight than mandatory
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* barriers, because mandatory barriers control MMIO effects on accesses
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* through relaxed memory I/O windows (which virtio-pci does not use). */
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#define virtio_mb(vq) \
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do { if ((vq)->weak_barriers) smp_mb(); else mb(); } while(0)
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#define virtio_rmb(vq) \
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do { if ((vq)->weak_barriers) smp_rmb(); else rmb(); } while(0)
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#define virtio_wmb(vq) \
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do { if ((vq)->weak_barriers) smp_wmb(); else wmb(); } while(0)
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#else
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/* We must force memory ordering even if guest is UP since host could be
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* running on another CPU, but SMP barriers are defined to barrier() in that
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* configuration. So fall back to mandatory barriers instead. */
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#define virtio_mb(vq) mb()
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#define virtio_rmb(vq) rmb()
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#define virtio_wmb(vq) wmb()
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#endif
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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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} while (0)
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#define END_USE(_vq) \
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do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } 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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/* Can we use weak barriers? */
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bool weak_barriers;
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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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/* Host publishes avail event idx */
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bool event;
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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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/* Figure out if their kicks are too delayed. */
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bool last_add_time_valid;
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ktime_t last_add_time;
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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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gfp_t gfp)
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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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/*
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* We require lowmem mappings for the descriptors because
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* otherwise virt_to_phys will give us bogus addresses in the
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* virtqueue.
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*/
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gfp &= ~(__GFP_HIGHMEM | __GFP_HIGH);
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desc = kmalloc((out + in) * sizeof(struct vring_desc), gfp);
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if (!desc)
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return -ENOMEM;
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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->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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/**
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* virtqueue_add_buf - expose buffer to other end
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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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*
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* Caller must ensure we don't call this with other virtqueue operations
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* at the same time (except where noted).
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*
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* Returns zero or a negative error (ie. ENOSPC, ENOMEM).
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*/
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int virtqueue_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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gfp_t gfp)
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{
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struct vring_virtqueue *vq = to_vvq(_vq);
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unsigned int i, avail, uninitialized_var(prev);
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int head;
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START_USE(vq);
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BUG_ON(data == NULL);
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#ifdef DEBUG
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{
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ktime_t now = ktime_get();
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/* No kick or get, with .1 second between? Warn. */
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if (vq->last_add_time_valid)
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WARN_ON(ktime_to_ms(ktime_sub(now, vq->last_add_time))
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> 100);
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vq->last_add_time = now;
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vq->last_add_time_valid = true;
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}
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#endif
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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->vq.num_free) {
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head = vring_add_indirect(vq, sg, out, in, gfp);
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if (likely(head >= 0))
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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->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->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->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). */
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avail = (vq->vring.avail->idx & (vq->vring.num-1));
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vq->vring.avail->ring[avail] = head;
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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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virtio_wmb(vq);
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vq->vring.avail->idx++;
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vq->num_added++;
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/* This is very unlikely, but theoretically possible. Kick
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* just in case. */
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if (unlikely(vq->num_added == (1 << 16) - 1))
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virtqueue_kick(_vq);
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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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return 0;
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}
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EXPORT_SYMBOL_GPL(virtqueue_add_buf);
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/**
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* virtqueue_kick_prepare - first half of split virtqueue_kick call.
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* @vq: the struct virtqueue
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*
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* Instead of virtqueue_kick(), you can do:
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* if (virtqueue_kick_prepare(vq))
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* virtqueue_notify(vq);
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*
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* This is sometimes useful because the virtqueue_kick_prepare() needs
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* to be serialized, but the actual virtqueue_notify() call does not.
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*/
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bool virtqueue_kick_prepare(struct virtqueue *_vq)
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{
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struct vring_virtqueue *vq = to_vvq(_vq);
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u16 new, old;
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bool needs_kick;
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START_USE(vq);
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/* We need to expose available array entries before checking avail
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* event. */
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virtio_mb(vq);
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old = vq->vring.avail->idx - vq->num_added;
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new = vq->vring.avail->idx;
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vq->num_added = 0;
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#ifdef DEBUG
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if (vq->last_add_time_valid) {
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WARN_ON(ktime_to_ms(ktime_sub(ktime_get(),
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vq->last_add_time)) > 100);
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}
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vq->last_add_time_valid = false;
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#endif
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if (vq->event) {
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needs_kick = vring_need_event(vring_avail_event(&vq->vring),
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new, old);
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} else {
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needs_kick = !(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY);
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}
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END_USE(vq);
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return needs_kick;
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}
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EXPORT_SYMBOL_GPL(virtqueue_kick_prepare);
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/**
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* virtqueue_notify - second half of split virtqueue_kick call.
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* @vq: the struct virtqueue
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*
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* This does not need to be serialized.
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*/
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void virtqueue_notify(struct virtqueue *_vq)
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{
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struct vring_virtqueue *vq = to_vvq(_vq);
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/* Prod other side to tell it about changes. */
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vq->notify(_vq);
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}
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EXPORT_SYMBOL_GPL(virtqueue_notify);
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/**
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* virtqueue_kick - update after add_buf
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* @vq: the struct virtqueue
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*
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* After one or more virtqueue_add_buf calls, invoke this to kick
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* the other side.
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*
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* Caller must ensure we don't call this with other virtqueue
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* operations at the same time (except where noted).
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*/
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void virtqueue_kick(struct virtqueue *vq)
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{
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if (virtqueue_kick_prepare(vq))
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virtqueue_notify(vq);
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}
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EXPORT_SYMBOL_GPL(virtqueue_kick);
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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->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->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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/**
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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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*
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* If the driver wrote data into the buffer, @len will be set to the
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* amount written. This means you don't need to clear the buffer
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* beforehand to ensure there's no data leakage in the case of short
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* writes.
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*
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* Caller must ensure we don't call this with other virtqueue
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* operations at the same time (except where noted).
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*
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* Returns NULL if there are no used buffers, or the "data" token
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* handed to virtqueue_add_buf().
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*/
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void *virtqueue_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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u16 last_used;
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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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/* Only get used array entries after they have been exposed by host. */
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virtio_rmb(vq);
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last_used = (vq->last_used_idx & (vq->vring.num - 1));
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i = vq->vring.used->ring[last_used].id;
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*len = vq->vring.used->ring[last_used].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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/* If we expect an interrupt for the next entry, tell host
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* by writing event index and flush out the write before
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* the read in the next get_buf call. */
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if (!(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)) {
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vring_used_event(&vq->vring) = vq->last_used_idx;
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virtio_mb(vq);
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}
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#ifdef DEBUG
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vq->last_add_time_valid = false;
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#endif
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END_USE(vq);
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return ret;
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}
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EXPORT_SYMBOL_GPL(virtqueue_get_buf);
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/**
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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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*
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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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*
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* Unlike other operations, this need not be serialized.
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*/
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void virtqueue_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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EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
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/**
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* virtqueue_enable_cb - restart callbacks after disable_cb.
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* @vq: the struct virtqueue we're talking about.
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*
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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.
|
|
*
|
|
* Caller must ensure we don't call this with other virtqueue
|
|
* operations at the same time (except where noted).
|
|
*/
|
|
bool virtqueue_enable_cb(struct virtqueue *_vq)
|
|
{
|
|
struct vring_virtqueue *vq = to_vvq(_vq);
|
|
|
|
START_USE(vq);
|
|
|
|
/* We optimistically turn back on interrupts, then check if there was
|
|
* more to do. */
|
|
/* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to
|
|
* either clear the flags bit or point the event index at the next
|
|
* entry. Always do both to keep code simple. */
|
|
vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
|
|
vring_used_event(&vq->vring) = vq->last_used_idx;
|
|
virtio_mb(vq);
|
|
if (unlikely(more_used(vq))) {
|
|
END_USE(vq);
|
|
return false;
|
|
}
|
|
|
|
END_USE(vq);
|
|
return true;
|
|
}
|
|
EXPORT_SYMBOL_GPL(virtqueue_enable_cb);
|
|
|
|
/**
|
|
* virtqueue_enable_cb_delayed - restart callbacks after disable_cb.
|
|
* @vq: the struct virtqueue we're talking about.
|
|
*
|
|
* This re-enables callbacks but hints to the other side to delay
|
|
* interrupts until most of the available buffers have been processed;
|
|
* it returns "false" if there are many pending buffers in the queue,
|
|
* to detect a possible race between the driver checking for more work,
|
|
* and enabling callbacks.
|
|
*
|
|
* Caller must ensure we don't call this with other virtqueue
|
|
* operations at the same time (except where noted).
|
|
*/
|
|
bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
|
|
{
|
|
struct vring_virtqueue *vq = to_vvq(_vq);
|
|
u16 bufs;
|
|
|
|
START_USE(vq);
|
|
|
|
/* We optimistically turn back on interrupts, then check if there was
|
|
* more to do. */
|
|
/* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to
|
|
* either clear the flags bit or point the event index at the next
|
|
* entry. Always do both to keep code simple. */
|
|
vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
|
|
/* TODO: tune this threshold */
|
|
bufs = (u16)(vq->vring.avail->idx - vq->last_used_idx) * 3 / 4;
|
|
vring_used_event(&vq->vring) = vq->last_used_idx + bufs;
|
|
virtio_mb(vq);
|
|
if (unlikely((u16)(vq->vring.used->idx - vq->last_used_idx) > bufs)) {
|
|
END_USE(vq);
|
|
return false;
|
|
}
|
|
|
|
END_USE(vq);
|
|
return true;
|
|
}
|
|
EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed);
|
|
|
|
/**
|
|
* virtqueue_detach_unused_buf - detach first unused buffer
|
|
* @vq: the struct virtqueue we're talking about.
|
|
*
|
|
* Returns NULL or the "data" token handed to virtqueue_add_buf().
|
|
* This is not valid on an active queue; it is useful only for device
|
|
* shutdown.
|
|
*/
|
|
void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
|
|
{
|
|
struct vring_virtqueue *vq = to_vvq(_vq);
|
|
unsigned int i;
|
|
void *buf;
|
|
|
|
START_USE(vq);
|
|
|
|
for (i = 0; i < vq->vring.num; i++) {
|
|
if (!vq->data[i])
|
|
continue;
|
|
/* detach_buf clears data, so grab it now. */
|
|
buf = vq->data[i];
|
|
detach_buf(vq, i);
|
|
vq->vring.avail->idx--;
|
|
END_USE(vq);
|
|
return buf;
|
|
}
|
|
/* That should have freed everything. */
|
|
BUG_ON(vq->vq.num_free != vq->vring.num);
|
|
|
|
END_USE(vq);
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf);
|
|
|
|
irqreturn_t vring_interrupt(int irq, void *_vq)
|
|
{
|
|
struct vring_virtqueue *vq = to_vvq(_vq);
|
|
|
|
if (!more_used(vq)) {
|
|
pr_debug("virtqueue interrupt with no work for %p\n", vq);
|
|
return IRQ_NONE;
|
|
}
|
|
|
|
if (unlikely(vq->broken))
|
|
return IRQ_HANDLED;
|
|
|
|
pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
|
|
if (vq->vq.callback)
|
|
vq->vq.callback(&vq->vq);
|
|
|
|
return IRQ_HANDLED;
|
|
}
|
|
EXPORT_SYMBOL_GPL(vring_interrupt);
|
|
|
|
struct virtqueue *vring_new_virtqueue(unsigned int index,
|
|
unsigned int num,
|
|
unsigned int vring_align,
|
|
struct virtio_device *vdev,
|
|
bool weak_barriers,
|
|
void *pages,
|
|
void (*notify)(struct virtqueue *),
|
|
void (*callback)(struct virtqueue *),
|
|
const char *name)
|
|
{
|
|
struct vring_virtqueue *vq;
|
|
unsigned int i;
|
|
|
|
/* We assume num is a power of 2. */
|
|
if (num & (num - 1)) {
|
|
dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
|
|
return NULL;
|
|
}
|
|
|
|
vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL);
|
|
if (!vq)
|
|
return NULL;
|
|
|
|
vring_init(&vq->vring, num, pages, vring_align);
|
|
vq->vq.callback = callback;
|
|
vq->vq.vdev = vdev;
|
|
vq->vq.name = name;
|
|
vq->vq.num_free = num;
|
|
vq->vq.index = index;
|
|
vq->notify = notify;
|
|
vq->weak_barriers = weak_barriers;
|
|
vq->broken = false;
|
|
vq->last_used_idx = 0;
|
|
vq->num_added = 0;
|
|
list_add_tail(&vq->vq.list, &vdev->vqs);
|
|
#ifdef DEBUG
|
|
vq->in_use = false;
|
|
vq->last_add_time_valid = false;
|
|
#endif
|
|
|
|
vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
|
|
vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
|
|
|
|
/* No callback? Tell other side not to bother us. */
|
|
if (!callback)
|
|
vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
|
|
|
|
/* Put everything in free lists. */
|
|
vq->free_head = 0;
|
|
for (i = 0; i < num-1; i++) {
|
|
vq->vring.desc[i].next = i+1;
|
|
vq->data[i] = NULL;
|
|
}
|
|
vq->data[i] = NULL;
|
|
|
|
return &vq->vq;
|
|
}
|
|
EXPORT_SYMBOL_GPL(vring_new_virtqueue);
|
|
|
|
void vring_del_virtqueue(struct virtqueue *vq)
|
|
{
|
|
list_del(&vq->list);
|
|
kfree(to_vvq(vq));
|
|
}
|
|
EXPORT_SYMBOL_GPL(vring_del_virtqueue);
|
|
|
|
/* Manipulates transport-specific feature bits. */
|
|
void vring_transport_features(struct virtio_device *vdev)
|
|
{
|
|
unsigned int i;
|
|
|
|
for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
|
|
switch (i) {
|
|
case VIRTIO_RING_F_INDIRECT_DESC:
|
|
break;
|
|
case VIRTIO_RING_F_EVENT_IDX:
|
|
break;
|
|
default:
|
|
/* We don't understand this bit. */
|
|
clear_bit(i, vdev->features);
|
|
}
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(vring_transport_features);
|
|
|
|
/**
|
|
* virtqueue_get_vring_size - return the size of the virtqueue's vring
|
|
* @vq: the struct virtqueue containing the vring of interest.
|
|
*
|
|
* Returns the size of the vring. This is mainly used for boasting to
|
|
* userspace. Unlike other operations, this need not be serialized.
|
|
*/
|
|
unsigned int virtqueue_get_vring_size(struct virtqueue *_vq)
|
|
{
|
|
|
|
struct vring_virtqueue *vq = to_vvq(_vq);
|
|
|
|
return vq->vring.num;
|
|
}
|
|
EXPORT_SYMBOL_GPL(virtqueue_get_vring_size);
|
|
|
|
MODULE_LICENSE("GPL");
|