Re: [PATCH v2 2/2] s390x/ap: Wire up the device request notifier interface

[Anthony Krowiak]

On 6/2/23 10:28 AM, Cédric Le Goater wrote:
> Hello Tony,
>
> On 6/2/23 16:11, Tony Krowiak wrote:
> > Let's wire up the device request notifier interface to handle device 
> > unplug
> > requests for AP.
> >
> > Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
> > Link: 
> > https://lore.kernel.org/qemu-devel/20230530225544.280031-1-akrowiak@linux.ibm.com/
> > ---
> >   hw/vfio/ap.c | 113 +++++++++++++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 113 insertions(+)
> >
> > diff --git a/hw/vfio/ap.c b/hw/vfio/ap.c
> > index e0dd561e85a3..6e21d1da5a70 100644
> > --- a/hw/vfio/ap.c
> > +++ b/hw/vfio/ap.c
> > @@ -18,6 +18,8 @@
> >   #include "hw/vfio/vfio-common.h"
> >   #include "hw/s390x/ap-device.h"
> >   #include "qemu/error-report.h"
> > +#include "qemu/event_notifier.h"
> > +#include "qemu/main-loop.h"
> >   #include "qemu/module.h"
> >   #include "qemu/option.h"
> >   #include "qemu/config-file.h"
> > @@ -33,6 +35,7 @@
> >   struct VFIOAPDevice {
> >       APDevice apdev;
> >       VFIODevice vdev;
> > +    EventNotifier req_notifier;
> >   };
> >   OBJECT_DECLARE_SIMPLE_TYPE(VFIOAPDevice, VFIO_AP_DEVICE)
> > @@ -84,10 +87,110 @@ static VFIOGroup *vfio_ap_get_group(VFIOAPDevice 
> > *vapdev, Error **errp)
> >       return vfio_get_group(groupid, &address_space_memory, errp);
> >   }
> > +static void vfio_ap_req_notifier_handler(void *opaque)
> > +{
> > +    VFIOAPDevice *vapdev = opaque;
> > +    Error *err = NULL;
> > +
> > +    if (!event_notifier_test_and_clear(&vapdev->req_notifier)) {
> > +        return;
> > +    }
> > +
> > +    qdev_unplug(DEVICE(vapdev), &err);
> > +
> > +    if (err) {
> > +        warn_reportf_err(err, VFIO_MSG_PREFIX, vapdev->vdev.name);
> > +    }
> > +}
> > +
> > +static void vfio_ap_register_irq_notifier(VFIOAPDevice *vapdev,
> > +                                          unsigned int irq, Error 
> > **errp)
> > +{
> > +    int fd;
> > +    size_t argsz;
> > +    IOHandler *fd_read;
> > +    EventNotifier *notifier;
> > +    struct vfio_irq_info *irq_info;
> > +    VFIODevice *vdev = &vapdev->vdev;
> > +
> > +    switch (irq) {
>
> Do you have plan for more interrupts ? If not, you could convert the
> 'switch' statement to a simple 'if' and remove the fd_read variable.

At this time there are no plans for further interrupts, but the switch 
does make it easy to add them:) On the other hand, I have no problem 
changing this to an 'if' statement. The fd_read variable is used below 
in the call to the qemu_set_fd_handler() function, so I can't get rid of it.

> > +    case VFIO_AP_REQ_IRQ_INDEX:
> > +        notifier = &vapdev->req_notifier;
> > +        fd_read = vfio_ap_req_notifier_handler;
> > +        break;
> > +    default:
> > +        error_setg(errp, "vfio: Unsupported device irq(%d)", irq);
> > +        return;
> > +    }
> > +
> > +    if (vdev->num_irqs < irq + 1) {
> > +        error_setg(errp, "vfio: IRQ %u not available (number of irqs 
> > %u)",
> > +                   irq, vdev->num_irqs);
> > +        return;
> > +    }
> > +
> > +    argsz = sizeof(*irq_info);
> > +    irq_info = g_malloc0(argsz);
> > +    irq_info->index = irq;
> > +    irq_info->argsz = argsz;
> > +
> > +    if (ioctl(vdev->fd, VFIO_DEVICE_GET_IRQ_INFO,
> > +              irq_info) < 0 || irq_info->count < 1) {
> > +        error_setg_errno(errp, errno, "vfio: Error getting irq info");
> > +        goto out_free_info;
> > +    }
> > +
> > +    if (event_notifier_init(notifier, 0)) {
> > +        error_setg_errno(errp, errno,
> > +                         "vfio: Unable to init event notifier for irq 
> > (%d)",
> > +                         irq);
> > +        goto out_free_info;
> > +    }
> > +
> > +    fd = event_notifier_get_fd(notifier);
> > +    qemu_set_fd_handler(fd, fd_read, NULL, vapdev);
> > +
> > +    if (vfio_set_irq_signaling(vdev, irq, 0, 
> > VFIO_IRQ_SET_ACTION_TRIGGER, fd,
> > +                               errp)) {
> > +        qemu_set_fd_handler(fd, NULL, NULL, vapdev);
> > +        event_notifier_cleanup(notifier);
> > +    }
> > +
> > +out_free_info:
> > +    g_free(irq_info);
> > +
> > +}
> > +
> > +static void vfio_ap_unregister_irq_notifier(VFIOAPDevice *vapdev,
> > +                                            unsigned int irq)
> > +{
> > +    Error *err = NULL;
> > +    EventNotifier *notifier;
> > +
> > +    switch (irq) {
> > +    case VFIO_AP_REQ_IRQ_INDEX:
> > +        notifier = &vapdev->req_notifier;
> > +        break;
> > +    default:
> > +        error_report("vfio: Unsupported device irq(%d)", irq);
> > +        return;
> > +    }
> > +
> > +    if (vfio_set_irq_signaling(&vapdev->vdev, irq, 0,
> > +                               VFIO_IRQ_SET_ACTION_TRIGGER, -1, &err)) {
> > +        warn_reportf_err(err, VFIO_MSG_PREFIX, vapdev->vdev.name);
> > +    }
> > +
> > +    qemu_set_fd_handler(event_notifier_get_fd(notifier),
> > +                        NULL, NULL, vapdev);
> > +    event_notifier_cleanup(notifier);
> > +}
> > +
> >   static void vfio_ap_realize(DeviceState *dev, Error **errp)
> >   {
> >       int ret;
> >       char *mdevid;
> > +    Error *err = NULL;
> >       VFIOGroup *vfio_group;
> >       APDevice *apdev = AP_DEVICE(dev);
> >       VFIOAPDevice *vapdev = VFIO_AP_DEVICE(apdev);
> > @@ -116,6 +219,15 @@ static void vfio_ap_realize(DeviceState *dev, 
> > Error **errp)
> >           goto out_get_dev_err;
> >       }
> > +    vfio_ap_register_irq_notifier(vapdev, VFIO_AP_REQ_IRQ_INDEX, &err);
> > +    if (err) {
> > +        /*
> > +         * Report this error, but do not make it a failing condition.
> > +         * Lack of this IRQ in the host does not prevent normal 
> > operation.
> > +         */
> > +        error_report_err(err);
>
> May be issue a warning instead ?

Given the comment above - i.e., not a failing condition - it probably 
makes sense to make it a warning.

> Thanks,
>
> C.
>
> > +    }
> > +
> >       return;
> >   out_get_dev_err:
> > @@ -129,6 +241,7 @@ static void vfio_ap_unrealize(DeviceState *dev)
> >       VFIOAPDevice *vapdev = VFIO_AP_DEVICE(apdev);
> >       VFIOGroup *group = vapdev->vdev.group;
> > +    vfio_ap_unregister_irq_notifier(vapdev, VFIO_AP_REQ_IRQ_INDEX);
> >       vfio_ap_put_device(vapdev);
> >       vfio_put_group(group);
> >   }