[RFC V5 PATCH 3/8] vhost: do not use vring_used_elem

From: Jason Wang
Date: Mon May 28 2018 - 22:13:30 EST

Instead of depending on the exported vring_used_elem, this patch
switches to use a new internal structure vhost_used_elem which embed
vring_used_elem in itself. This could be used to let vhost to record
extra metadata for the incoming packed ring layout.

Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
drivers/vhost/net.c | 19 +++++++-------
drivers/vhost/scsi.c | 10 ++++----
drivers/vhost/vhost.c | 68 ++++++++++++---------------------------------------
drivers/vhost/vhost.h | 18 ++++++++------
drivers/vhost/vsock.c | 6 ++---
5 files changed, 45 insertions(+), 76 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 826489c..3826f1f 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -341,10 +341,10 @@ static void vhost_zerocopy_signal_used(struct vhost_net *net,
int j = 0;

for (i = nvq->done_idx; i != nvq->upend_idx; i = (i + 1) % UIO_MAXIOV) {
- if (vq->heads[i].len == VHOST_DMA_FAILED_LEN)
+ if (vq->heads[i].elem.len == VHOST_DMA_FAILED_LEN)
vhost_net_tx_err(net);
- if (VHOST_DMA_IS_DONE(vq->heads[i].len)) {
- vq->heads[i].len = VHOST_DMA_CLEAR_LEN;
+ if (VHOST_DMA_IS_DONE(vq->heads[i].elem.len)) {
+ vq->heads[i].elem.len = VHOST_DMA_CLEAR_LEN;
++j;
} else
break;
@@ -367,7 +367,7 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success)
rcu_read_lock_bh();

/* set len to mark this desc buffers done DMA */
- vq->heads[ubuf->desc].len = success ?
+ vq->heads[ubuf->desc].elem.len = success ?
VHOST_DMA_DONE_LEN : VHOST_DMA_FAILED_LEN;
cnt = vhost_net_ubuf_put(ubufs);

@@ -426,7 +426,7 @@ static int vhost_net_enable_vq(struct vhost_net *n,

static int vhost_net_tx_get_vq_desc(struct vhost_net *net,
struct vhost_virtqueue *vq,
- struct vring_used_elem *used_elem,
+ struct vhost_used_elem *used_elem,
struct iovec iov[], unsigned int iov_size,
unsigned int *out_num, unsigned int *in_num)
{
@@ -477,7 +477,7 @@ static void handle_tx(struct vhost_net *net)
size_t hdr_size;
struct socket *sock;
struct vhost_net_ubuf_ref *uninitialized_var(ubufs);
- struct vring_used_elem used;
+ struct vhost_used_elem used;
bool zcopy, zcopy_used;
int sent_pkts = 0;

@@ -542,9 +542,10 @@ static void handle_tx(struct vhost_net *net)
struct ubuf_info *ubuf;
ubuf = nvq->ubuf_info + nvq->upend_idx;

- vq->heads[nvq->upend_idx].id =
- cpu_to_vhost32(vq, used.id);
- vq->heads[nvq->upend_idx].len = VHOST_DMA_IN_PROGRESS;
+ vq->heads[nvq->upend_idx].elem.id =
+ cpu_to_vhost32(vq, used.elem.id);
+ vq->heads[nvq->upend_idx].elem.len =
+ VHOST_DMA_IN_PROGRESS;
ubuf->callback = vhost_zerocopy_callback;
ubuf->ctx = nvq->ubufs;
ubuf->desc = nvq->upend_idx;
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 654c71f..ac11412 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -67,7 +67,7 @@ struct vhost_scsi_inflight {

struct vhost_scsi_cmd {
/* Descriptor from vhost_get_vq_desc() for virt_queue segment */
- struct vring_used_elem tvc_vq_used;
+ struct vhost_used_elem tvc_vq_used;
/* virtio-scsi initiator task attribute */
int tvc_task_attr;
/* virtio-scsi response incoming iovecs */
@@ -441,7 +441,7 @@ vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
struct virtio_scsi_event *event = &evt->event;
struct virtio_scsi_event __user *eventp;
- struct vring_used_elem used;
+ struct vhost_used_elem used;
unsigned out, in;
int ret;

@@ -785,7 +785,7 @@ static void vhost_scsi_submission_work(struct work_struct *work)
static void
vhost_scsi_send_bad_target(struct vhost_scsi *vs,
struct vhost_virtqueue *vq,
- struct vring_used_elem *used, unsigned out)
+ struct vhost_used_elem *used, unsigned out)
{
struct virtio_scsi_cmd_resp __user *resp;
struct virtio_scsi_cmd_resp rsp;
@@ -808,7 +808,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
struct virtio_scsi_cmd_req v_req;
struct virtio_scsi_cmd_req_pi v_req_pi;
struct vhost_scsi_cmd *cmd;
- struct vring_used_elem used;
+ struct vhost_used_elem used;
struct iov_iter out_iter, in_iter, prot_iter, data_iter;
u64 tag;
u32 exp_data_len, data_direction;
@@ -837,7 +837,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
ARRAY_SIZE(vq->iov), &out, &in,
NULL, NULL);
pr_debug("vhost_get_vq_desc: head: %d, out: %u in: %u\n",
- used.id, out, in);
+ used.elem.id, out, in);
/* Nothing new? Wait for eventfd to tell us they refilled. */
if (ret == -ENOSPC) {
if (unlikely(vhost_enable_notify(&vs->dev, vq))) {
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 296bd5e..2b2a776 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -728,41 +728,6 @@ static bool memory_access_ok(struct vhost_dev *d, struct vhost_umem *umem,
static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
struct iovec iov[], int iov_size, int access);

-static int vhost_copy_to_user(struct vhost_virtqueue *vq, void __user *to,
- const void *from, unsigned size)
-{
- int ret;
-
- if (!vq->iotlb)
- return __copy_to_user(to, from, size);
- else {
- /* This function should be called after iotlb
- * prefetch, which means we're sure that all vq
- * could be access through iotlb. So -EAGAIN should
- * not happen in this case.
- */
- struct iov_iter t;
- void __user *uaddr = vhost_vq_meta_fetch(vq,
- (u64)(uintptr_t)to, size,
- VHOST_ADDR_USED);
-
- if (uaddr)
- return __copy_to_user(uaddr, from, size);
-
- ret = translate_desc(vq, (u64)(uintptr_t)to, size, vq->iotlb_iov,
- ARRAY_SIZE(vq->iotlb_iov),
- VHOST_ACCESS_WO);
- if (ret < 0)
- goto out;
- iov_iter_init(&t, WRITE, vq->iotlb_iov, ret, size);
- ret = copy_to_iter(from, size, &t);
- if (ret == size)
- ret = 0;
- }
-out:
- return ret;
-}
-
static int vhost_copy_from_user(struct vhost_virtqueue *vq, void *to,
void __user *from, unsigned size)
{
@@ -1958,7 +1923,7 @@ static int get_indirect(struct vhost_virtqueue *vq,
* never a valid descriptor number) if none was found. A negative code is
* returned on error. */
int vhost_get_vq_desc(struct vhost_virtqueue *vq,
- struct vring_used_elem *used,
+ struct vhost_used_elem *used,
struct iovec iov[], unsigned int iov_size,
unsigned int *out_num, unsigned int *in_num,
struct vhost_log *log, unsigned int *log_num)
@@ -2009,7 +1974,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
return -EFAULT;
}

- used->id = ring_head;
+ used->elem.id = ring_head;
head = vhost16_to_cpu(vq, ring_head);

/* If their number is silly, that's an error. */
@@ -2103,9 +2068,9 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
EXPORT_SYMBOL_GPL(vhost_get_vq_desc);

static void vhost_set_used_len(struct vhost_virtqueue *vq,
- struct vring_used_elem *used, int len)
+ struct vhost_used_elem *used, int len)
{
- used->len = cpu_to_vhost32(vq, len);
+ used->elem.len = cpu_to_vhost32(vq, len);
}

/* This is a multi-buffer version of vhost_get_desc, that works if
@@ -2119,7 +2084,7 @@ static void vhost_set_used_len(struct vhost_virtqueue *vq,
* returns number of buffer heads allocated, negative on error
*/
int vhost_get_bufs(struct vhost_virtqueue *vq,
- struct vring_used_elem *heads,
+ struct vhost_used_elem *heads,
int datalen,
unsigned *iovcount,
struct vhost_log *log,
@@ -2192,7 +2157,7 @@ EXPORT_SYMBOL_GPL(vhost_discard_vq_desc);

/* After we've used one of their buffers, we tell them about it. We'll then
* want to notify the guest, using eventfd. */
-int vhost_add_used(struct vhost_virtqueue *vq, struct vring_used_elem *used,
+int vhost_add_used(struct vhost_virtqueue *vq, struct vhost_used_elem *used,
int len)
{
vhost_set_used_len(vq, used, len);
@@ -2201,27 +2166,26 @@ int vhost_add_used(struct vhost_virtqueue *vq, struct vring_used_elem *used,
EXPORT_SYMBOL_GPL(vhost_add_used);

static int __vhost_add_used_n(struct vhost_virtqueue *vq,
- struct vring_used_elem *heads,
+ struct vhost_used_elem *heads,
unsigned count)
{
struct vring_used_elem __user *used;
u16 old, new;
- int start;
+ int start, i;

start = vq->last_used_idx & (vq->num - 1);
used = vq->used->ring + start;
- if (count == 1) {
- if (vhost_put_user(vq, heads[0].id, &used->id)) {
+ for (i = 0; i < count; i++) {
+ if (unlikely(vhost_put_user(vq, heads[i].elem.id,
+ &used[i].id))) {
vq_err(vq, "Failed to write used id");
return -EFAULT;
}
- if (vhost_put_user(vq, heads[0].len, &used->len)) {
+ if (unlikely(vhost_put_user(vq, heads[i].elem.len,
+ &used[i].len))) {
vq_err(vq, "Failed to write used len");
return -EFAULT;
}
- } else if (vhost_copy_to_user(vq, used, heads, count * sizeof *used)) {
- vq_err(vq, "Failed to write used");
- return -EFAULT;
}
if (unlikely(vq->log_used)) {
/* Make sure data is seen before log. */
@@ -2245,7 +2209,7 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq,

/* After we've used one of their buffers, we tell them about it. We'll then
* want to notify the guest, using eventfd. */
-int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
+int vhost_add_used_n(struct vhost_virtqueue *vq, struct vhost_used_elem *heads,
unsigned count)
{
int start, n, r;
@@ -2329,7 +2293,7 @@ EXPORT_SYMBOL_GPL(vhost_signal);
/* And here's the combo meal deal. Supersize me! */
void vhost_add_used_and_signal(struct vhost_dev *dev,
struct vhost_virtqueue *vq,
- struct vring_used_elem *used, int len)
+ struct vhost_used_elem *used, int len)
{
vhost_add_used(vq, used, len);
vhost_signal(dev, vq);
@@ -2339,7 +2303,7 @@ EXPORT_SYMBOL_GPL(vhost_add_used_and_signal);
/* multi-buffer version of vhost_add_used_and_signal */
void vhost_add_used_and_signal_n(struct vhost_dev *dev,
struct vhost_virtqueue *vq,
- struct vring_used_elem *heads, unsigned count)
+ struct vhost_used_elem *heads, unsigned count)
{
vhost_add_used_n(vq, heads, count);
vhost_signal(dev, vq);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index a7cc7e7..8dea44b 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -34,6 +34,10 @@ struct vhost_poll {
struct vhost_dev *dev;
};

+struct vhost_used_elem {
+ struct vring_used_elem elem;
+};
+
void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn);
void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work);
bool vhost_has_work(struct vhost_dev *dev);
@@ -126,7 +130,7 @@ struct vhost_virtqueue {
struct iovec iov[UIO_MAXIOV];
struct iovec iotlb_iov[64];
struct iovec *indirect;
- struct vring_used_elem *heads;
+ struct vhost_used_elem *heads;
/* Protected by virtqueue mutex. */
struct vhost_umem *umem;
struct vhost_umem *iotlb;
@@ -182,12 +186,12 @@ bool vhost_vq_access_ok(struct vhost_virtqueue *vq);
bool vhost_log_access_ok(struct vhost_dev *);

int vhost_get_vq_desc(struct vhost_virtqueue *,
- struct vring_used_elem *used_elem,
+ struct vhost_used_elem *used_elem,
struct iovec iov[], unsigned int iov_count,
unsigned int *out_num, unsigned int *in_num,
struct vhost_log *log, unsigned int *log_num);
int vhost_get_bufs(struct vhost_virtqueue *vq,
- struct vring_used_elem *heads,
+ struct vhost_used_elem *heads,
int datalen,
unsigned *iovcount,
struct vhost_log *log,
@@ -198,13 +202,13 @@ void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);

int vhost_vq_init_access(struct vhost_virtqueue *);
int vhost_add_used(struct vhost_virtqueue *vq,
- struct vring_used_elem *elem, int len);
-int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads,
+ struct vhost_used_elem *elem, int len);
+int vhost_add_used_n(struct vhost_virtqueue *vq, struct vhost_used_elem *heads,
unsigned count);
void vhost_add_used_and_signal(struct vhost_dev *, struct vhost_virtqueue *,
- struct vring_used_elem *, int len);
+ struct vhost_used_elem *, int len);
void vhost_add_used_and_signal_n(struct vhost_dev *, struct vhost_virtqueue *,
- struct vring_used_elem *heads, unsigned count);
+ struct vhost_used_elem *heads, unsigned count);
void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *);
void vhost_disable_notify(struct vhost_dev *, struct vhost_virtqueue *);
bool vhost_vq_avail_empty(struct vhost_dev *, struct vhost_virtqueue *);
diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 59a01cd..695694f 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -98,7 +98,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,

for (;;) {
struct virtio_vsock_pkt *pkt;
- struct vring_used_elem used;
+ struct vhost_used_elem used;
struct iov_iter iov_iter;
unsigned out, in;
size_t nbytes;
@@ -146,7 +146,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
break;
}

- len = vhost32_to_cpu(vq, used.len);
+ len = vhost32_to_cpu(vq, used.elem.len);
iov_iter_init(&iov_iter, READ, &vq->iov[out], in, len);

nbytes = copy_to_iter(&pkt->hdr, sizeof(pkt->hdr), &iov_iter);
@@ -346,7 +346,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
dev);
struct virtio_vsock_pkt *pkt;
- struct vring_used_elem used;
+ struct vhost_used_elem used;
int ret;
unsigned int out, in;
bool added = false;
--
2.7.4