vfio: ccw: return I/O results asynchronously

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>
Message-Id: <20170317031743.40128-13-bjsdjshi@linux.vnet.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index b5971d3216977c1f6abb4c98f3a510b2be661e0f..3e0a40ec8ade475ca4d7785da57eb5daeb140928 100644 (file)
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -20,6 +20,8 @@
 #include "css.h"
 #include "vfio_ccw_private.h"
 
+struct workqueue_struct *vfio_ccw_work_q;
+
 /*
  * Helpers
  */
@@ -52,6 +54,7 @@ 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);
                };
 
@@ -63,18 +66,12 @@ out_unlock:
        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;
 
@@ -89,7 +86,7 @@ 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;
@@ -109,15 +106,26 @@ 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. */
@@ -126,7 +134,6 @@ 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;
 
@@ -147,12 +154,8 @@ 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;
@@ -229,8 +232,8 @@ 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);
@@ -269,7 +272,7 @@ 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);
        atomic_set(&private->avail, 1);
 
        return 0;
@@ -367,10 +370,16 @@ 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;
 }
@@ -379,6 +388,7 @@ 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 1294c534741087ddca00112a81f18a8c9ffcb98a..d754d3d905743f35e6ee84b85068579a769f81f7 100644 (file)
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -202,9 +202,6 @@ 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 dddab52913edd8a240e23cfeaad42a66ba987133..2503797fb1530f48f8d183874766188d37b1b311 100644 (file)
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -12,6 +12,7 @@
 
 #include <linux/completion.h>
 #include <linux/eventfd.h>
+#include <linux/workqueue.h>
 #include <linux/vfio_ccw.h>
 
 #include "css.h"
@@ -25,12 +26,11 @@
  * @mdev: pointer 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: channel 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;
@@ -40,13 +40,12 @@ struct vfio_ccw_private {
        struct notifier_block   nb;
        struct ccw_io_region    io_region;
 
-       wait_queue_head_t       wait_q;
-       u32                     intparm;
        struct channel_program  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);