[PATCH RFC v2 12/15] vfio: ccw: return I/O results asynchronously

Dong Jia Shi
2017-01-12T07:19:44Z

Introduce a singlethreaded workqueue to handle the I/O interrupts.
With the work added to this queue, we store the I/O results to the
io_region of the subchannel, then signal the userspace program to
handle the results.

Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
---
drivers/s390/cio/vfio_ccw_drv.c | 58 ++++++++++++++++++++++---------------
drivers/s390/cio/vfio_ccw_ops.c | 3 --
drivers/s390/cio/vfio_ccw_private.h | 7 ++---
3 files changed, 37 insertions(+), 31 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 595dcb4..56af313 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -24,6 +24,8 @@
#include "css.h"
#include "vfio_ccw_private.h"

+struct workqueue_struct *vfio_ccw_work_q;
+
/*
* Helpers
*/
@@ -56,6 +58,7 @@ int vfio_ccw_sch_quiesce(struct subchannel *sch)

spin_lock_irq(sch->lock);
private->completion = NULL;
+ flush_workqueue(vfio_ccw_work_q);
ret = cio_cancel_halt_clear(sch, &iretry);
};

@@ -67,18 +70,12 @@ int vfio_ccw_sch_quiesce(struct subchannel *sch)
return ret;
}

-static int doing_io(struct vfio_ccw_private *private, u32 intparm)
-{
- return (private->intparm == intparm);
-}
-
static int vfio_ccw_sch_io_helper(struct vfio_ccw_private *private)
{
struct subchannel *sch;
union orb *orb;
int ccode;
__u8 lpm;
- u32 intparm;

sch = private->sch;

@@ -93,7 +90,7 @@ static int vfio_ccw_sch_io_helper(struct vfio_ccw_private *private)
* Initialize device status information
*/
sch->schib.scsw.cmd.actl |= SCSW_ACTL_START_PEND;
- break;
+ return 0;
case 1: /* Status pending */
case 2: /* Busy */
return -EBUSY;
@@ -113,15 +110,26 @@ static int vfio_ccw_sch_io_helper(struct vfio_ccw_private *private)
default:
return ccode;
}
+}

- intparm = (u32)(addr_t)sch;
- private->intparm = 0;
- wait_event(private->wait_q, doing_io(private, intparm));
+static void vfio_ccw_sch_io_todo(struct work_struct *work)
+{
+ struct vfio_ccw_private *private;
+ struct subchannel *sch;
+ struct irb *irb;

- if (scsw_is_solicited(&private->irb.scsw))
- cp_update_scsw(&private->cp, &private->irb.scsw);
+ private = container_of(work, struct vfio_ccw_private, io_work);
+ irb = &private->irb;
+ sch = private->sch;

- return 0;
+ if (scsw_is_solicited(&irb->scsw)) {
+ cp_update_scsw(&private->cp, &irb->scsw);
+ cp_free(&private->cp);
+ }
+ memcpy(private->io_region.irb_area, irb, sizeof(*irb));
+
+ if (private->io_trigger)
+ eventfd_signal(private->io_trigger, 1);
}

/* Deal with the ccw command request from the userspace. */
@@ -130,7 +138,6 @@ int vfio_ccw_sch_cmd_request(struct vfio_ccw_private *private)
struct mdev_device *mdev = private->mdev;
union orb *orb;
union scsw *scsw = &private->scsw;
- struct irb *irb = &private->irb;
struct ccw_io_region *io_region = &private->io_region;
int ret;

@@ -151,12 +158,8 @@ int vfio_ccw_sch_cmd_request(struct vfio_ccw_private *private)

/* Start channel program and wait for I/O interrupt. */
ret = vfio_ccw_sch_io_helper(private);
- if (!ret) {
- /* Get irb info and copy it to irb_area. */
- memcpy(io_region->irb_area, irb, sizeof(*irb));
- }
-
- cp_free(&private->cp);
+ if (!ret)
+ cp_free(&private->cp);
} else if (scsw->cmd.fctl & SCSW_FCTL_HALT_FUNC) {
/* XXX: Handle halt. */
ret = -EOPNOTSUPP;
@@ -233,8 +236,8 @@ static void vfio_ccw_sch_irq(struct subchannel *sch)

irb = this_cpu_ptr(&cio_irb);
memcpy(&private->irb, irb, sizeof(*irb));
- private->intparm = (u32)(addr_t)sch;
- wake_up(&private->wait_q);
+
+ queue_work(vfio_ccw_work_q, &private->io_work);

if (private->completion)
complete(private->completion);
@@ -273,7 +276,7 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
if (ret)
goto out_rm_group;

- init_waitqueue_head(&private->wait_q);
+ INIT_WORK(&private->io_work, vfio_ccw_sch_io_todo);

return 0;

@@ -370,10 +373,16 @@ static int __init vfio_ccw_sch_init(void)
{
int ret;

+ vfio_ccw_work_q = create_singlethread_workqueue("vfio-ccw");
+ if (!vfio_ccw_work_q)
+ return -ENOMEM;
+
isc_register(VFIO_CCW_ISC);
ret = css_driver_register(&vfio_ccw_sch_driver);
- if (ret)
+ if (ret) {
isc_unregister(VFIO_CCW_ISC);
+ destroy_workqueue(vfio_ccw_work_q);
+ }

return ret;
}
@@ -382,6 +391,7 @@ static void __exit vfio_ccw_sch_exit(void)
{
css_driver_unregister(&vfio_ccw_sch_driver);
isc_unregister(VFIO_CCW_ISC);
+ destroy_workqueue(vfio_ccw_work_q);
}
module_init(vfio_ccw_sch_init);
module_exit(vfio_ccw_sch_exit);
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index 3c47eb6..f1b17c4 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -203,9 +203,6 @@ static ssize_t vfio_ccw_mdev_write(struct mdev_device *mdev,
if (region->ret_code != 0)
return region->ret_code;

- if (private->io_trigger)
- eventfd_signal(private->io_trigger, 1);
-
return count;
}

diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index d551d98..2e5ce86 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -16,6 +16,7 @@

#include <linux/completion.h>
#include <linux/eventfd.h>
+#include <linux/workqueue.h>
#include <asm/vfio_ccw.h>

#include "css.h"
@@ -28,12 +29,11 @@
* @mdev: pointor to the mediated device
* @nb: notifier for vfio events
* @io_region: MMIO region to input/output I/O arguments/results
- * @wait_q: wait for interrupt
- * @intparm: record current interrupt parameter, used for wait interrupt
* @cp: ccw program for the current I/O operation
* @irb: irb info received from interrupt
* @scsw: scsw info
* @io_trigger: eventfd ctx for signaling userspace I/O results
+ * @io_work: work for deferral process of I/O handling
*/
struct vfio_ccw_private {
struct subchannel *sch;
@@ -42,13 +42,12 @@ struct vfio_ccw_private {
struct notifier_block nb;
struct ccw_io_region io_region;

- wait_queue_head_t wait_q;
- u32 intparm;
struct ccwprogram cp;
struct irb irb;
union scsw scsw;

struct eventfd_ctx *io_trigger;
+ struct work_struct io_work;
} __aligned(8);

extern int vfio_ccw_mdev_reg(struct subchannel *sch);
--
2.8.4