Hi Jan,
On 28/09/2020 11:58, Jan Beulich wrote:
Before and after XSA-342 there has been an asymmetry in how not really
usable ports get treated in do_poll(): Ones beyond a certain boundary
(max_evtchns originally, valid_evtchns subsequently) did get refused
with -EINVAL, while lower ones were accepted despite there potentially
being no way to wake the vCPU again from its polling state. Arrange to
also honor evtchn_usable() output in the decision.
Requested-by: Andrew Cooper <andrew.coop...@citrix.com>
Signed-off-by: Jan Beulich <jbeul...@suse.com>
With one request (see below):
Reviewed-by: Julien Grall <jgr...@amazon.com>
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -1427,13 +1427,13 @@ static long do_poll(struct sched_poll *s
if ( __copy_from_guest_offset(&port, sched_poll->ports, i, 1) )
goto out;
- rc = -EINVAL;
- if ( !port_is_valid(d, port) )
- goto out;
-
- rc = 0;
- if ( evtchn_port_is_pending(d, port) )
+ rc = evtchn_port_poll(d, port);
+ if ( rc )
+ {
+ if ( rc > 0 )
+ rc = 0;
This check wasn't obvious to me until I spent some times understanding
how evtchn_port_poll() is working. I think it would be worth to...
goto out;
+ }
}
if ( sched_poll->nr_ports == 1 )
--- a/xen/include/xen/event.h
+++ b/xen/include/xen/event.h
@@ -240,19 +240,6 @@ static inline bool evtchn_is_pending(con
return evtchn_usable(evtchn) && d->evtchn_port_ops->is_pending(d, evtchn);
}
-static inline bool evtchn_port_is_pending(struct domain *d, evtchn_port_t port)
-{
- struct evtchn *evtchn = evtchn_from_port(d, port);
- bool rc;
- unsigned long flags;
-
- spin_lock_irqsave(&evtchn->lock, flags);
- rc = evtchn_is_pending(d, evtchn);
- spin_unlock_irqrestore(&evtchn->lock, flags);
-
- return rc;
-}
-
static inline bool evtchn_is_masked(const struct domain *d,
const struct evtchn *evtchn)
{
@@ -279,6 +266,24 @@ static inline bool evtchn_is_busy(const
d->evtchn_port_ops->is_busy(d, evtchn);
}
+static inline int evtchn_port_poll(struct domain *d, evtchn_port_t port)
... add a comment on top of evtchn_port_poll() explaining that it will
return a value < 0 if the port is not valid and > 0 if the port is pending.
+{
+ int rc = -EINVAL;
+
+ if ( port_is_valid(d, port) )
+ {
+ struct evtchn *evtchn = evtchn_from_port(d, port);
+ unsigned long flags;
+
+ spin_lock_irqsave(&evtchn->lock, flags);
+ if ( evtchn_usable(evtchn) )
+ rc = evtchn_is_pending(d, evtchn);
+ spin_unlock_irqrestore(&evtchn->lock, flags);
+ }
+
+ return rc;
+}
+
static inline int evtchn_port_set_priority(struct domain *d,
struct evtchn *evtchn,
unsigned int priority)
Cheers,
--
Julien Grall
