From: Eric Farman <farman@linux.ibm.com>
To: Cornelia Huck <cohuck@redhat.com>, Halil Pasic <pasic@linux.ibm.com>
Cc: Matthew Rosato <mjrosato@linux.ibm.com>,
Jared Rossi <jrossi@linux.ibm.com>,
linux-s390@vger.kernel.org, kvm@vger.kernel.org,
Eric Farman <farman@linux.ibm.com>
Subject: [RFC PATCH v4 4/4] vfio-ccw: Reset FSM state to IDLE before io_mutex
Date: Tue, 13 Apr 2021 20:24:10 +0200 [thread overview]
Message-ID: <20210413182410.1396170-5-farman@linux.ibm.com> (raw)
In-Reply-To: <20210413182410.1396170-1-farman@linux.ibm.com>
Today, the stacked call to vfio_ccw_sch_io_todo() does three things:
1) Update a solicited IRB with CP information, and release the CP
if the interrupt was the end of a START operation.
2) Copy the IRB data into the io_region, under the protection of
the io_mutex
3) Reset the vfio-ccw FSM state to IDLE to acknowledge that
vfio-ccw can accept more work.
The trouble is that step 3 is (A) invoked for both solicited and
unsolicited interrupts, and (B) sitting after the mutex for step 2.
This second piece becomes a problem if it processes an interrupt
for a CLEAR SUBCHANNEL while another thread initiates a START,
thus allowing the CP and FSM states to get out of sync. That is:
CPU 1 CPU 2
fsm_do_clear()
fsm_irq()
fsm_io_request()
fsm_io_helper()
vfio_ccw_sch_io_todo()
fsm_irq()
vfio_ccw_sch_io_todo()
Let's move the reset of the FSM state to the point where the
channel_program struct is cleaned up, which is only done for
solicited interrupts anyway.
Signed-off-by: Eric Farman <farman@linux.ibm.com>
---
drivers/s390/cio/vfio_ccw_drv.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 8c625b530035..e51318f23ca8 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -94,16 +94,15 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work)
(SCSW_ACTL_DEVACT | SCSW_ACTL_SCHACT));
if (scsw_is_solicited(&irb->scsw)) {
cp_update_scsw(&private->cp, &irb->scsw);
- if (is_final && private->state == VFIO_CCW_STATE_CP_PENDING)
+ if (is_final && private->state == VFIO_CCW_STATE_CP_PENDING) {
cp_free(&private->cp);
+ private->state = VFIO_CCW_STATE_IDLE;
+ }
}
mutex_lock(&private->io_mutex);
memcpy(private->io_region->irb_area, irb, sizeof(*irb));
mutex_unlock(&private->io_mutex);
- if (private->mdev && is_final)
- private->state = VFIO_CCW_STATE_IDLE;
-
if (private->io_trigger)
eventfd_signal(private->io_trigger, 1);
}
--
2.25.1
next prev parent reply other threads:[~2021-04-13 18:24 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-13 18:24 [RFC PATCH v4 0/4] vfio-ccw: Fix interrupt handling for HALT/CLEAR Eric Farman
2021-04-13 18:24 ` [RFC PATCH v4 1/4] vfio-ccw: Check initialized flag in cp_init() Eric Farman
2021-04-14 16:30 ` Cornelia Huck
2021-04-13 18:24 ` [RFC PATCH v4 2/4] vfio-ccw: Check workqueue before doing START Eric Farman
2021-04-15 10:51 ` Cornelia Huck
2021-04-15 13:48 ` Eric Farman
2021-04-15 16:19 ` Cornelia Huck
2021-04-15 18:42 ` Eric Farman
2021-04-16 14:41 ` Cornelia Huck
2021-04-13 18:24 ` [RFC PATCH v4 3/4] vfio-ccw: Reset FSM state to IDLE inside FSM Eric Farman
2021-04-15 10:54 ` Cornelia Huck
2021-04-13 18:24 ` Eric Farman [this message]
2021-04-21 10:25 ` [RFC PATCH v4 4/4] vfio-ccw: Reset FSM state to IDLE before io_mutex Cornelia Huck
2021-04-21 12:58 ` Eric Farman
2021-04-22 16:16 ` Eric Farman
2021-04-22 0:52 ` [RFC PATCH v4 0/4] vfio-ccw: Fix interrupt handling for HALT/CLEAR Halil Pasic
2021-04-22 20:49 ` Eric Farman
2021-04-23 11:06 ` Cornelia Huck
2021-04-23 13:23 ` Halil Pasic
2021-04-23 13:28 ` Niklas Schnelle
2021-04-23 15:53 ` Eric Farman
2021-04-23 11:50 ` Halil Pasic
2021-04-23 15:53 ` Eric Farman
2021-04-23 17:08 ` Halil Pasic
2021-04-23 19:07 ` Eric Farman
2021-04-24 0:18 ` Halil Pasic
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