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Re: [libvirt] [RFC v1 4/6] migration: Migration support for ephemeral hostdevs




On 05/13/2015 04:36 PM, Peter Krempa wrote:
On Wed, May 13, 2015 at 11:36:30 +0800, Chen Fan wrote:
add migration support for ephemeral host devices, introduce
two 'detach' and 'restore' functions to unplug/plug host devices
during migration.

Signed-off-by: Chen Fan <chen fan fnst cn fujitsu com>
---
  src/qemu/qemu_migration.c | 171 ++++++++++++++++++++++++++++++++++++++++++++--
  src/qemu/qemu_migration.h |   9 +++
  src/qemu/qemu_process.c   |  11 +++
  3 files changed, 187 insertions(+), 4 deletions(-)

diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index 56112f9..d5a698f 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -3384,6 +3384,158 @@ qemuMigrationPrepareDef(virQEMUDriverPtr driver,
      return def;
  }
+int
+qemuMigrationDetachEphemeralDevices(virQEMUDriverPtr driver,
+                                    virDomainObjPtr vm,
+                                    bool live)
+{
+    qemuDomainObjPrivatePtr priv = vm->privateData;
+    virDomainHostdevDefPtr hostdev;
+    virDomainNetDefPtr net;
+    virDomainDeviceDef dev;
+    virDomainDeviceDefPtr dev_copy = NULL;
+    virCapsPtr caps = NULL;
+    int actualType;
+    int ret = -1;
+    size_t i;
+
+    VIR_DEBUG("Rum domain detach ephemeral devices");
+
+    if (!(caps = virQEMUDriverGetCapabilities(driver, false)))
+        return ret;
+
+    for (i = 0; i < vm->def->nnets;) {
+        net = vm->def->nets[i];
+
+        actualType = virDomainNetGetActualType(net);
+        if (actualType != VIR_DOMAIN_NET_TYPE_HOSTDEV) {
+            i++;
+            continue;
+        }
+
+        hostdev = virDomainNetGetActualHostdev(net);
+        if (hostdev->mode != VIR_DOMAIN_HOSTDEV_MODE_SUBSYS ||
+            hostdev->source.subsys.type != VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_PCI ||
+            !hostdev->ephemeral) {
+            i++;
+            continue;
+        }
+
+        dev.type = VIR_DOMAIN_DEVICE_NET;
+        dev.data.net = net;
+
+        dev_copy = virDomainDeviceDefCopy(&dev, vm->def,
+                                          caps, driver->xmlopt);
+        if (!dev_copy)
+            goto cleanup;
+
+        if (live) {
+            /* nnets reduced */
+            if (qemuDomainDetachNetDevice(driver, vm, dev_copy) < 0)
+                goto cleanup;
So this is where the fun begins. qemuDomainDetachNetDevice is not
designed to be called this way since the detach API where it's used
normally returns 0 in the following two cases:

1) The detach was successfull, the guest removed the device
2) The detach request was successful, but guest did not remove the
device yet

In the latter case you need to wait for a event to successfully know
when the device was removed. Since this might very well happen the code
will need to be changed to take that option into account. Please note
that that step will make all the things really complicated.

did you said the event is "DEVICE_DELETED" ?
I saw the code  the funcition qemuDomainWaitForDeviceRemoval
has been used for waiting device removed from guest.

Thanks,
Chen



Peter



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