Re: [PATCH v2 10/13] xen/pvcalls: implement poll command
On Wed, 26 Jul 2017, Boris Ostrovsky wrote:
> On 07/25/2017 05:22 PM, Stefano Stabellini wrote:
> > For active sockets, check the indexes and use the inflight_conn_req
> > waitqueue to wait.
> >
> > For passive sockets, send PVCALLS_POLL to the backend. Use the
> > inflight_accept_req waitqueue if an accept is outstanding. Otherwise use
> > the inflight_req waitqueue: inflight_req is awaken when a new response
> > is received; on wakeup we check whether the POLL response is arrived by
> > looking at the PVCALLS_FLAG_POLL_RET flag. We set the flag from
> > pvcalls_front_event_handler, if the response was for a POLL command.
> >
> > In pvcalls_front_event_handler, get the struct socket pointer from the
> > poll id (we previously converted struct socket* to uint64_t and used it
> > as id).
> >
> > Signed-off-by: Stefano Stabellini
> > CC: boris.ostrov...@oracle.com
> > CC: jgr...@suse.com
> > ---
> > drivers/xen/pvcalls-front.c | 134
> >
> > drivers/xen/pvcalls-front.h | 3 +
> > 2 files changed, 126 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> > index b4ca569..833b717 100644
> > --- a/drivers/xen/pvcalls-front.c
> > +++ b/drivers/xen/pvcalls-front.c
> > @@ -130,17 +130,35 @@ static irqreturn_t pvcalls_front_event_handler(int
> > irq, void *dev_id)
> > rsp = RING_GET_RESPONSE(&bedata->ring, bedata->ring.rsp_cons);
> >
> > req_id = rsp->req_id;
> > - src = (uint8_t *)&bedata->rsp[req_id];
> > - src += sizeof(rsp->req_id);
> > - dst = (uint8_t *)rsp;
> > - dst += sizeof(rsp->req_id);
> > - memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id));
> > - /*
> > -* First copy the rest of the data, then req_id. It is
> > -* paired with the barrier when accessing bedata->rsp.
> > -*/
> > - smp_wmb();
> > - WRITE_ONCE(bedata->rsp[req_id].req_id, rsp->req_id);
> > + if (rsp->cmd == PVCALLS_POLL) {
> > + struct socket *sock = (struct socket *) rsp->u.poll.id;
> > + struct sock_mapping *map =
> > + (struct sock_mapping *)
> > + READ_ONCE(sock->sk->sk_send_head);
> > +
> > + set_bit(PVCALLS_FLAG_POLL_RET,
> > + (void *)&map->passive.flags);
> > + /*
> > +* Set RET, then clear INFLIGHT. It pairs with
> > +* the checks at the beginning of
> > +* pvcalls_front_poll_passive.
> > +*/
> > + smp_wmb();
>
> virt_wmb() (here, below, and I think I saw it somewhere else)
This smp_wmb is an internal barrier to the frontend, it doesn't
synchronize with the backend. It synchronizes only within the frontend.
A uniprocessor frontend wouldn't actually need this barrier. I admit it
is a bit confusing, I'll add a comment about this.
> > + clear_bit(PVCALLS_FLAG_POLL_INFLIGHT,
> > + (void *)&map->passive.flags);
> > + } else {
> > + src = (uint8_t *)&bedata->rsp[req_id];
> > + src += sizeof(rsp->req_id);
> > + dst = (uint8_t *)rsp;
> > + dst += sizeof(rsp->req_id);
> > + memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id));
> > + /*
> > +* First copy the rest of the data, then req_id. It is
> > +* paired with the barrier when accessing bedata->rsp.
> > +*/
> > + smp_wmb();
> > + WRITE_ONCE(bedata->rsp[req_id].req_id, rsp->req_id);
> > + }
> >
> > done = 1;
> > bedata->ring.rsp_cons++;
> > @@ -707,6 +725,100 @@ int pvcalls_front_accept(struct socket *sock, struct
> > socket *newsock, int flags)
> > return ret;
> > }
> >
> > +static unsigned int pvcalls_front_poll_passive(struct file *file,
> > + struct pvcalls_bedata *bedata,
> > + struct sock_mapping *map,
> > + poll_table *wait)
> > +{
> > + int notify, req_id;
> > + struct xen_pvcalls_request *req;
> > +
> > + if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
> > +(void *)&map->passive.flags)) {
> > + poll_wait(file, &map->passive.inflight_accept_req, wait);
> > + return 0;
> > + }
> > +
> > + if (test_and_clear_bit(PVCALLS_FLAG_POLL_RET,
> > + (void *)&map->passive.flags))
> > + return POLLIN;
> > +
> > + /*
> > +* First check RET, then INFLIGHT. No barriers necessary to
> > +* ensure execution ordering because of the conditional
> > +* instructions creating control depende
Re: [PATCH v2 10/13] xen/pvcalls: implement poll command
On 07/25/2017 05:22 PM, Stefano Stabellini wrote:
> For active sockets, check the indexes and use the inflight_conn_req
> waitqueue to wait.
>
> For passive sockets, send PVCALLS_POLL to the backend. Use the
> inflight_accept_req waitqueue if an accept is outstanding. Otherwise use
> the inflight_req waitqueue: inflight_req is awaken when a new response
> is received; on wakeup we check whether the POLL response is arrived by
> looking at the PVCALLS_FLAG_POLL_RET flag. We set the flag from
> pvcalls_front_event_handler, if the response was for a POLL command.
>
> In pvcalls_front_event_handler, get the struct socket pointer from the
> poll id (we previously converted struct socket* to uint64_t and used it
> as id).
>
> Signed-off-by: Stefano Stabellini
> CC: boris.ostrov...@oracle.com
> CC: jgr...@suse.com
> ---
> drivers/xen/pvcalls-front.c | 134
>
> drivers/xen/pvcalls-front.h | 3 +
> 2 files changed, 126 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
> index b4ca569..833b717 100644
> --- a/drivers/xen/pvcalls-front.c
> +++ b/drivers/xen/pvcalls-front.c
> @@ -130,17 +130,35 @@ static irqreturn_t pvcalls_front_event_handler(int irq,
> void *dev_id)
> rsp = RING_GET_RESPONSE(&bedata->ring, bedata->ring.rsp_cons);
>
> req_id = rsp->req_id;
> - src = (uint8_t *)&bedata->rsp[req_id];
> - src += sizeof(rsp->req_id);
> - dst = (uint8_t *)rsp;
> - dst += sizeof(rsp->req_id);
> - memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id));
> - /*
> - * First copy the rest of the data, then req_id. It is
> - * paired with the barrier when accessing bedata->rsp.
> - */
> - smp_wmb();
> - WRITE_ONCE(bedata->rsp[req_id].req_id, rsp->req_id);
> + if (rsp->cmd == PVCALLS_POLL) {
> + struct socket *sock = (struct socket *) rsp->u.poll.id;
> + struct sock_mapping *map =
> + (struct sock_mapping *)
> + READ_ONCE(sock->sk->sk_send_head);
> +
> + set_bit(PVCALLS_FLAG_POLL_RET,
> + (void *)&map->passive.flags);
> + /*
> + * Set RET, then clear INFLIGHT. It pairs with
> + * the checks at the beginning of
> + * pvcalls_front_poll_passive.
> + */
> + smp_wmb();
virt_wmb() (here, below, and I think I saw it somewhere else)
> + clear_bit(PVCALLS_FLAG_POLL_INFLIGHT,
> + (void *)&map->passive.flags);
> + } else {
> + src = (uint8_t *)&bedata->rsp[req_id];
> + src += sizeof(rsp->req_id);
> + dst = (uint8_t *)rsp;
> + dst += sizeof(rsp->req_id);
> + memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id));
> + /*
> + * First copy the rest of the data, then req_id. It is
> + * paired with the barrier when accessing bedata->rsp.
> + */
> + smp_wmb();
> + WRITE_ONCE(bedata->rsp[req_id].req_id, rsp->req_id);
> + }
>
> done = 1;
> bedata->ring.rsp_cons++;
> @@ -707,6 +725,100 @@ int pvcalls_front_accept(struct socket *sock, struct
> socket *newsock, int flags)
> return ret;
> }
>
> +static unsigned int pvcalls_front_poll_passive(struct file *file,
> +struct pvcalls_bedata *bedata,
> +struct sock_mapping *map,
> +poll_table *wait)
> +{
> + int notify, req_id;
> + struct xen_pvcalls_request *req;
> +
> + if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
> + (void *)&map->passive.flags)) {
> + poll_wait(file, &map->passive.inflight_accept_req, wait);
> + return 0;
> + }
> +
> + if (test_and_clear_bit(PVCALLS_FLAG_POLL_RET,
> +(void *)&map->passive.flags))
> + return POLLIN;
> +
> + /*
> + * First check RET, then INFLIGHT. No barriers necessary to
> + * ensure execution ordering because of the conditional
> + * instructions creating control dependencies.
> + */
> +
> + if (test_and_set_bit(PVCALLS_FLAG_POLL_INFLIGHT,
> + (void *)&map->passive.flags)) {
> + poll_wait(file, &bedata->inflight_req, wait);
> + return 0;
> + }
> +
> + spin_lock(&bedata->pvcallss_lock);
> + req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
> + if (RING_FULL(&bedata-
[PATCH v2 10/13] xen/pvcalls: implement poll command
For active sockets, check the indexes and use the inflight_conn_req
waitqueue to wait.
For passive sockets, send PVCALLS_POLL to the backend. Use the
inflight_accept_req waitqueue if an accept is outstanding. Otherwise use
the inflight_req waitqueue: inflight_req is awaken when a new response
is received; on wakeup we check whether the POLL response is arrived by
looking at the PVCALLS_FLAG_POLL_RET flag. We set the flag from
pvcalls_front_event_handler, if the response was for a POLL command.
In pvcalls_front_event_handler, get the struct socket pointer from the
poll id (we previously converted struct socket* to uint64_t and used it
as id).
Signed-off-by: Stefano Stabellini
CC: boris.ostrov...@oracle.com
CC: jgr...@suse.com
---
drivers/xen/pvcalls-front.c | 134
drivers/xen/pvcalls-front.h | 3 +
2 files changed, 126 insertions(+), 11 deletions(-)
diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index b4ca569..833b717 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -130,17 +130,35 @@ static irqreturn_t pvcalls_front_event_handler(int irq,
void *dev_id)
rsp = RING_GET_RESPONSE(&bedata->ring, bedata->ring.rsp_cons);
req_id = rsp->req_id;
- src = (uint8_t *)&bedata->rsp[req_id];
- src += sizeof(rsp->req_id);
- dst = (uint8_t *)rsp;
- dst += sizeof(rsp->req_id);
- memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id));
- /*
-* First copy the rest of the data, then req_id. It is
-* paired with the barrier when accessing bedata->rsp.
-*/
- smp_wmb();
- WRITE_ONCE(bedata->rsp[req_id].req_id, rsp->req_id);
+ if (rsp->cmd == PVCALLS_POLL) {
+ struct socket *sock = (struct socket *) rsp->u.poll.id;
+ struct sock_mapping *map =
+ (struct sock_mapping *)
+ READ_ONCE(sock->sk->sk_send_head);
+
+ set_bit(PVCALLS_FLAG_POLL_RET,
+ (void *)&map->passive.flags);
+ /*
+* Set RET, then clear INFLIGHT. It pairs with
+* the checks at the beginning of
+* pvcalls_front_poll_passive.
+*/
+ smp_wmb();
+ clear_bit(PVCALLS_FLAG_POLL_INFLIGHT,
+ (void *)&map->passive.flags);
+ } else {
+ src = (uint8_t *)&bedata->rsp[req_id];
+ src += sizeof(rsp->req_id);
+ dst = (uint8_t *)rsp;
+ dst += sizeof(rsp->req_id);
+ memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id));
+ /*
+* First copy the rest of the data, then req_id. It is
+* paired with the barrier when accessing bedata->rsp.
+*/
+ smp_wmb();
+ WRITE_ONCE(bedata->rsp[req_id].req_id, rsp->req_id);
+ }
done = 1;
bedata->ring.rsp_cons++;
@@ -707,6 +725,100 @@ int pvcalls_front_accept(struct socket *sock, struct
socket *newsock, int flags)
return ret;
}
+static unsigned int pvcalls_front_poll_passive(struct file *file,
+ struct pvcalls_bedata *bedata,
+ struct sock_mapping *map,
+ poll_table *wait)
+{
+ int notify, req_id;
+ struct xen_pvcalls_request *req;
+
+ if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
+(void *)&map->passive.flags)) {
+ poll_wait(file, &map->passive.inflight_accept_req, wait);
+ return 0;
+ }
+
+ if (test_and_clear_bit(PVCALLS_FLAG_POLL_RET,
+ (void *)&map->passive.flags))
+ return POLLIN;
+
+ /*
+* First check RET, then INFLIGHT. No barriers necessary to
+* ensure execution ordering because of the conditional
+* instructions creating control dependencies.
+*/
+
+ if (test_and_set_bit(PVCALLS_FLAG_POLL_INFLIGHT,
+(void *)&map->passive.flags)) {
+ poll_wait(file, &bedata->inflight_req, wait);
+ return 0;
+ }
+
+ spin_lock(&bedata->pvcallss_lock);
+ req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
+ if (RING_FULL(&bedata->ring) ||
+ READ_ONCE(bedata->rsp[req_id].req_id) != PVCALLS_INVALID_ID) {
+ spin_unlock(&bedata->pvcallss_lock);
+ return -EAGAIN;
+ }
+ req = RIN
