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Re: [Qemu-devel] [PATCH v4 4/5] s390x/vfio: ap: Introduce VFIO AP device


From: Tony Krowiak
Subject: Re: [Qemu-devel] [PATCH v4 4/5] s390x/vfio: ap: Introduce VFIO AP device
Date: Thu, 26 Apr 2018 10:50:06 -0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0

On 04/23/2018 03:00 AM, Cornelia Huck wrote:
On Sun, 22 Apr 2018 12:05:44 -0400
Tony Krowiak <address@hidden> wrote:

On 04/19/2018 08:03 AM, Cornelia Huck wrote:
On Sun, 15 Apr 2018 15:07:23 -0400
Tony Krowiak <address@hidden> wrote:
Introduces a VFIO based AP device. The device is defined via
the QEMU command line by specifying:

      -device vfio-ap,sysfsdev=<path-to-mediated-matrix-device>

There may be only one vfio-ap device configured for a guest.

The mediated matrix device is created by the VFIO AP device
driver by writing a UUID to a sysfs attribute file (see
docs/vfio-ap.txt). The mediated matrix device will be named
after the UUID. Symbolic links to the $uuid are created in
many places, so the path to the mediated matrix device $uuid
can be specified in any of the following ways:

/sys/devices/vfio_ap/matrix/$uuid
/sys/devices/vfio_ap/matrix/mdev_supported_types/vfio_ap-passthrough/devices/$uuid
/sys/bus/mdev/devices/$uuid
/sys/bus/mdev/drivers/vfio_mdev/$uuid

When the vfio-ap device is realized, it acquires and opens the
VFIO iommu group to which the mediated matrix device is
bound. This causes a VFIO group notification event to be
signaled. The vfio_ap device driver's group notification
handler will get called at which time the device driver
will configure the the AP devices to which the guest will
be granted access.

Signed-off-by: Tony Krowiak <address@hidden>
---
   default-configs/s390x-softmmu.mak |    1 +
   hw/vfio/Makefile.objs             |    1 +
   hw/vfio/ap.c                      |  191 
+++++++++++++++++++++++++++++++++++++
   include/hw/vfio/vfio-common.h     |    1 +
   4 files changed, 194 insertions(+), 0 deletions(-)
   create mode 100644 hw/vfio/ap.c
+static void vfio_ap_realize(DeviceState *dev, Error **errp)
+{
+    VFIODevice *vbasedev;
+    VFIOGroup *vfio_group;
+    APDevice *apdev = DO_UPCAST(APDevice, parent_obj, dev);
+    char *mdevid;
+    Error *local_err = NULL;
+    int ret;
+
+    /*
+     * Since a guest's matrix is configured in its entirety by the mediated
+     * matrix device and hot plug is not currently supported, there is no
+     * need to have more than one vfio-ap device. Check if a vfio-ap device
+     * has already been defined.
+     */
+    if (vfio_apdev) {
+        error_setg(&local_err, "Only one %s device is allowed",
+                   VFIO_AP_DEVICE_TYPE);
+        goto out_err;
+    }
+
+    if (!s390_has_feat(S390_FEAT_AP)) {
+        error_setg(&local_err, "AP support not enabled");
+        goto out_err;
+    }
+
+    vfio_apdev = DO_UPCAST(VFIOAPDevice, apdev, apdev);
+
+    vfio_group = vfio_ap_get_group(vfio_apdev, &local_err);
+    if (!vfio_group) {
+        goto out_err;
+    }
+
+    vfio_apdev->vdev.ops = &vfio_ap_ops;
+    vfio_apdev->vdev.type = VFIO_DEVICE_TYPE_AP;
+    mdevid = basename(vfio_apdev->vdev.sysfsdev);
+    vfio_apdev->vdev.name = g_strdup_printf("%s", mdevid);
+    vfio_apdev->vdev.dev = dev;
+    QLIST_FOREACH(vbasedev, &vfio_group->device_list, next) {
+        if (strcmp(vbasedev->name, vfio_apdev->vdev.name) == 0) {
+            error_setg(&local_err,
+                       "%s: AP device %s has already been realized",
+                       VFIO_AP_DEVICE_TYPE, vfio_apdev->vdev.name);
+            goto out_device_err;
+        }
+    }
+
+    ret = vfio_get_device(vfio_group, mdevid, &vfio_apdev->vdev, &local_err);
+    if (ret) {
+        goto out_device_err;
+    }
Don't you need a put somewhere to avoid memory leaks?
There is a call to vfio_put_device in the unrealize function.
I don't think unrealize is called if realize failed, so you need to
clean up in the error cases?

Very true. I  misinterpreted your point. Yes, I need to clean up
if realize fails.


+
+    return;
+
+
+out_device_err:
+    vfio_put_group(vfio_group);
+out_err:
+    vfio_apdev = NULL;
+    error_propagate(errp, local_err);
+}





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