Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxxxxxxxxxx>
---
hw/dataplane/vring.h | 8 +++++--
hw/virtio-blk.c | 62 ++++++++++++++++++++++++++++++++++++++++++--------
2 files changed, 59 insertions(+), 11 deletions(-)
diff --git a/hw/dataplane/vring.h b/hw/dataplane/vring.h
index 7099a99..b07d4f6 100644
--- a/hw/dataplane/vring.h
+++ b/hw/dataplane/vring.h
@@ -76,7 +76,7 @@ static void vring_setup(Vring *vring, VirtIODevice *vdev, int n)
* Stolen from linux-2.6/drivers/vhost/vhost.c.
*/
static unsigned int vring_pop(Vring *vring,
- struct iovec iov[], unsigned int iov_size,
+ struct iovec iov[], struct iovec *iov_end,
unsigned int *out_num, unsigned int *in_num)
{
struct vring_desc desc;
@@ -138,10 +138,14 @@ static unsigned int vring_pop(Vring *vring,
return ret;
}
continue; */
- fprintf(stderr, "virtio-blk indirect vring not supported\n");
+ fprintf(stderr, "Indirect vring not supported\n");
exit(1);
}
+ if (iov >= iov_end) {
+ fprintf(stderr, "Not enough vring iovecs\n");
+ exit(1);
+ }
iov->iov_base = phys_to_host(vring, desc.addr);
iov->iov_len = desc.len;
iov++;
diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index 2c1cce8..91f1bab 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -24,6 +24,7 @@
enum {
SEG_MAX = 126, /* maximum number of I/O segments */
VRING_MAX = SEG_MAX + 2, /* maximum number of vring descriptors */
+ REQ_MAX = VRING_MAX / 2, /* maximum number of requests in the vring */
};
typedef struct VirtIOBlock
@@ -58,20 +59,63 @@ static void handle_io(EventHandler *handler)
fprintf(stderr, "io completion happened\n");
}
+static void process_request(struct iovec iov[], unsigned int out_num, unsigned int in_num)
+{
+ /* Virtio block requests look like this: */
+ struct virtio_blk_outhdr *outhdr; /* iov[0] */
+ /* data[] ... */
+ struct virtio_blk_inhdr *inhdr; /* iov[out_num + in_num - 1] */
+
+ if (unlikely(out_num == 0 || in_num == 0 ||
+ iov[0].iov_len != sizeof *outhdr ||
+ iov[out_num + in_num - 1].iov_len != sizeof *inhdr)) {
+ fprintf(stderr, "virtio-blk invalid request\n");
+ exit(1);
+ }
+
+ outhdr = iov[0].iov_base;
+ inhdr = iov[out_num + in_num - 1].iov_base;
+
+ fprintf(stderr, "virtio-blk request type=%#x sector=%#lx\n",
+ outhdr->type, outhdr->sector);
+}
+
static void handle_notify(EventHandler *handler)
{
VirtIOBlock *s = container_of(handler, VirtIOBlock, notify_handler);
- struct iovec iov[VRING_MAX];
- unsigned int out_num, in_num;
- int head;
- head = vring_pop(&s->vring, iov, ARRAY_SIZE(iov), &out_num, &in_num);
- if (unlikely(head >= vring_get_num(&s->vring))) {
- fprintf(stderr, "false alarm, nothing on vring\n");
- return;
- }
+ /* There is one array of iovecs into which all new requests are extracted
+ * from the vring. Requests are read from the vring and the translated
+ * descriptors are written to the iovecs array. The iovecs do not have to
+ * persist across handle_notify() calls because the kernel copies the
+ * iovecs on io_submit().
+ *
+ * Handling io_submit() EAGAIN may require storing the requests across
+ * handle_notify() calls until the kernel has sufficient resources to
+ * accept more I/O. This is not implemented yet.
+ */
+ struct iovec iovec[VRING_MAX];
+ struct iovec *iov, *end = &iovec[VRING_MAX];
+
+ /* When a request is read from the vring, the index of the first descriptor
+ * (aka head) is returned so that the completed request can be pushed onto
+ * the vring later.
+ *
+ * The number of hypervisor read-only iovecs is out_num. The number of
+ * hypervisor write-only iovecs is in_num.
+ */
+ unsigned int head, out_num = 0, in_num = 0;
+
+ for (iov = iovec; ; iov += out_num + in_num) {
+ head = vring_pop(&s->vring, iov, end, &out_num, &in_num);
+ if (head >= vring_get_num(&s->vring)) {
+ break; /* no more requests */
+ }
+
+ fprintf(stderr, "head=%u out_num=%u in_num=%u\n", head, out_num, in_num);
- fprintf(stderr, "head=%u out_num=%u in_num=%u\n", head, out_num, in_num);
+ process_request(iov, out_num, in_num);
+ }
}
static void *data_plane_thread(void *opaque)
--
1.7.10.4
--
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