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Diffstat (limited to 'drivers/virtio/virtio_ring.c')
-rw-r--r--drivers/virtio/virtio_ring.c532
1 files changed, 532 insertions, 0 deletions
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
new file mode 100644
index 00000000..68b91368
--- /dev/null
+++ b/drivers/virtio/virtio_ring.c
@@ -0,0 +1,532 @@
+/* Virtio ring implementation.
+ *
+ * Copyright 2007 Rusty Russell IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+#include <linux/virtio.h>
+#include <linux/virtio_ring.h>
+#include <linux/virtio_config.h>
+#include <linux/device.h>
+#include <linux/slab.h>
+
+/* virtio guest is communicating with a virtual "device" that actually runs on
+ * a host processor. Memory barriers are used to control SMP effects. */
+#ifdef CONFIG_SMP
+/* Where possible, use SMP barriers which are more lightweight than mandatory
+ * barriers, because mandatory barriers control MMIO effects on accesses
+ * through relaxed memory I/O windows (which virtio does not use). */
+#define virtio_mb() smp_mb()
+#define virtio_rmb() smp_rmb()
+#define virtio_wmb() smp_wmb()
+#else
+/* We must force memory ordering even if guest is UP since host could be
+ * running on another CPU, but SMP barriers are defined to barrier() in that
+ * configuration. So fall back to mandatory barriers instead. */
+#define virtio_mb() mb()
+#define virtio_rmb() rmb()
+#define virtio_wmb() wmb()
+#endif
+
+#ifdef DEBUG
+/* For development, we want to crash whenever the ring is screwed. */
+#define BAD_RING(_vq, fmt, args...) \
+ do { \
+ dev_err(&(_vq)->vq.vdev->dev, \
+ "%s:"fmt, (_vq)->vq.name, ##args); \
+ BUG(); \
+ } while (0)
+/* Caller is supposed to guarantee no reentry. */
+#define START_USE(_vq) \
+ do { \
+ if ((_vq)->in_use) \
+ panic("%s:in_use = %i\n", \
+ (_vq)->vq.name, (_vq)->in_use); \
+ (_vq)->in_use = __LINE__; \
+ } while (0)
+#define END_USE(_vq) \
+ do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0)
+#else
+#define BAD_RING(_vq, fmt, args...) \
+ do { \
+ dev_err(&_vq->vq.vdev->dev, \
+ "%s:"fmt, (_vq)->vq.name, ##args); \
+ (_vq)->broken = true; \
+ } while (0)
+#define START_USE(vq)
+#define END_USE(vq)
+#endif
+
+struct vring_virtqueue
+{
+ struct virtqueue vq;
+
+ /* Actual memory layout for this queue */
+ struct vring vring;
+
+ /* Other side has made a mess, don't try any more. */
+ bool broken;
+
+ /* Host supports indirect buffers */
+ bool indirect;
+
+ /* Host publishes avail event idx */
+ bool event;
+
+ /* Number of free buffers */
+ unsigned int num_free;
+ /* Head of free buffer list. */
+ unsigned int free_head;
+ /* Number we've added since last sync. */
+ unsigned int num_added;
+
+ /* Last used index we've seen. */
+ u16 last_used_idx;
+
+ /* How to notify other side. FIXME: commonalize hcalls! */
+ void (*notify)(struct virtqueue *vq);
+
+#ifdef DEBUG
+ /* They're supposed to lock for us. */
+ unsigned int in_use;
+#endif
+
+ /* Tokens for callbacks. */
+ void *data[];
+};
+
+#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
+
+/* Set up an indirect table of descriptors and add it to the queue. */
+static int vring_add_indirect(struct vring_virtqueue *vq,
+ struct scatterlist sg[],
+ unsigned int out,
+ unsigned int in,
+ gfp_t gfp)
+{
+ struct vring_desc *desc;
+ unsigned head;
+ int i;
+
+ desc = kmalloc((out + in) * sizeof(struct vring_desc), gfp);
+ if (!desc)
+ return -ENOMEM;
+
+ /* Transfer entries from the sg list into the indirect page */
+ for (i = 0; i < out; i++) {
+ desc[i].flags = VRING_DESC_F_NEXT;
+ desc[i].addr = sg_phys(sg);
+ desc[i].len = sg->length;
+ desc[i].next = i+1;
+ sg++;
+ }
+ for (; i < (out + in); i++) {
+ desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
+ desc[i].addr = sg_phys(sg);
+ desc[i].len = sg->length;
+ desc[i].next = i+1;
+ sg++;
+ }
+
+ /* Last one doesn't continue. */
+ desc[i-1].flags &= ~VRING_DESC_F_NEXT;
+ desc[i-1].next = 0;
+
+ /* We're about to use a buffer */
+ vq->num_free--;
+
+ /* Use a single buffer which doesn't continue */
+ head = vq->free_head;
+ vq->vring.desc[head].flags = VRING_DESC_F_INDIRECT;
+ vq->vring.desc[head].addr = virt_to_phys(desc);
+ vq->vring.desc[head].len = i * sizeof(struct vring_desc);
+
+ /* Update free pointer */
+ vq->free_head = vq->vring.desc[head].next;
+
+ return head;
+}
+
+int virtqueue_add_buf_gfp(struct virtqueue *_vq,
+ struct scatterlist sg[],
+ unsigned int out,
+ unsigned int in,
+ void *data,
+ gfp_t gfp)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ unsigned int i, avail, uninitialized_var(prev);
+ int head;
+
+ START_USE(vq);
+
+ BUG_ON(data == NULL);
+
+ /* If the host supports indirect descriptor tables, and we have multiple
+ * buffers, then go indirect. FIXME: tune this threshold */
+ if (vq->indirect && (out + in) > 1 && vq->num_free) {
+ head = vring_add_indirect(vq, sg, out, in, gfp);
+ if (likely(head >= 0))
+ goto add_head;
+ }
+
+ BUG_ON(out + in > vq->vring.num);
+ BUG_ON(out + in == 0);
+
+ if (vq->num_free < out + in) {
+ pr_debug("Can't add buf len %i - avail = %i\n",
+ out + in, vq->num_free);
+ /* FIXME: for historical reasons, we force a notify here if
+ * there are outgoing parts to the buffer. Presumably the
+ * host should service the ring ASAP. */
+ if (out)
+ vq->notify(&vq->vq);
+ END_USE(vq);
+ return -ENOSPC;
+ }
+
+ /* We're about to use some buffers from the free list. */
+ vq->num_free -= out + in;
+
+ head = vq->free_head;
+ for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) {
+ vq->vring.desc[i].flags = VRING_DESC_F_NEXT;
+ vq->vring.desc[i].addr = sg_phys(sg);
+ vq->vring.desc[i].len = sg->length;
+ prev = i;
+ sg++;
+ }
+ for (; in; i = vq->vring.desc[i].next, in--) {
+ vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
+ vq->vring.desc[i].addr = sg_phys(sg);
+ vq->vring.desc[i].len = sg->length;
+ prev = i;
+ sg++;
+ }
+ /* Last one doesn't continue. */
+ vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT;
+
+ /* Update free pointer */
+ vq->free_head = i;
+
+add_head:
+ /* Set token. */
+ vq->data[head] = data;
+
+ /* Put entry in available array (but don't update avail->idx until they
+ * do sync). FIXME: avoid modulus here? */
+ avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num;
+ vq->vring.avail->ring[avail] = head;
+
+ pr_debug("Added buffer head %i to %p\n", head, vq);
+ END_USE(vq);
+
+ return vq->num_free;
+}
+EXPORT_SYMBOL_GPL(virtqueue_add_buf_gfp);
+
+void virtqueue_kick(struct virtqueue *_vq)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ u16 new, old;
+ START_USE(vq);
+ /* Descriptors and available array need to be set before we expose the
+ * new available array entries. */
+ virtio_wmb();
+
+ old = vq->vring.avail->idx;
+ new = vq->vring.avail->idx = old + vq->num_added;
+ vq->num_added = 0;
+
+ /* Need to update avail index before checking if we should notify */
+ virtio_mb();
+
+ if (vq->event ?
+ vring_need_event(vring_avail_event(&vq->vring), new, old) :
+ !(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
+ /* Prod other side to tell it about changes. */
+ vq->notify(&vq->vq);
+
+ END_USE(vq);
+}
+EXPORT_SYMBOL_GPL(virtqueue_kick);
+
+static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
+{
+ unsigned int i;
+
+ /* Clear data ptr. */
+ vq->data[head] = NULL;
+
+ /* Put back on free list: find end */
+ i = head;
+
+ /* Free the indirect table */
+ if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT)
+ kfree(phys_to_virt(vq->vring.desc[i].addr));
+
+ while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
+ i = vq->vring.desc[i].next;
+ vq->num_free++;
+ }
+
+ vq->vring.desc[i].next = vq->free_head;
+ vq->free_head = head;
+ /* Plus final descriptor */
+ vq->num_free++;
+}
+
+static inline bool more_used(const struct vring_virtqueue *vq)
+{
+ return vq->last_used_idx != vq->vring.used->idx;
+}
+
+void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+ void *ret;
+ unsigned int i;
+
+ START_USE(vq);
+
+ if (unlikely(vq->broken)) {
+ END_USE(vq);
+ return NULL;
+ }
+
+ if (!more_used(vq)) {
+ pr_debug("No more buffers in queue\n");
+ END_USE(vq);
+ return NULL;
+ }
+
+ /* Only get used array entries after they have been exposed by host. */
+ virtio_rmb();
+
+ i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
+ *len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;
+
+ if (unlikely(i >= vq->vring.num)) {
+ BAD_RING(vq, "id %u out of range\n", i);
+ return NULL;
+ }
+ if (unlikely(!vq->data[i])) {
+ BAD_RING(vq, "id %u is not a head!\n", i);
+ return NULL;
+ }
+
+ /* detach_buf clears data, so grab it now. */
+ ret = vq->data[i];
+ detach_buf(vq, i);
+ vq->last_used_idx++;
+ /* If we expect an interrupt for the next entry, tell host
+ * by writing event index and flush out the write before
+ * the read in the next get_buf call. */
+ if (!(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)) {
+ vring_used_event(&vq->vring) = vq->last_used_idx;
+ virtio_mb();
+ }
+
+ END_USE(vq);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(virtqueue_get_buf);
+
+void virtqueue_disable_cb(struct virtqueue *_vq)
+{
+ struct vring_virtqueue *vq = to_vvq(_vq);
+
+ vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
+}
+EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
+
+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();
+ if (unlikely(more_used(vq))) {
+ END_USE(vq);
+ return false;
+ }
+
+ END_USE(vq);
+ return true;
+}
+EXPORT_SYMBOL_GPL(virtqueue_enable_cb);
+
+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();
+ 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);
+
+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->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 num,
+ unsigned int vring_align,
+ struct virtio_device *vdev,
+ 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->notify = notify;
+ 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;
+#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->num_free = num;
+ 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);
+
+MODULE_LICENSE("GPL");
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