Re: [PATCH 8/8] qemu: Add support for hot/cold-(un)plug of shmem devices

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On Fri, Oct 14, 2016 at 10:25:26AM -0400, John Ferlan wrote:

[...]


+int
+qemuDomainDetachShmemDevice(virQEMUDriverPtr driver,
+                            virDomainObjPtr vm,
+                            virDomainDeviceDefPtr dev)
+{
+    int ret = -1;
+    ssize_t idx = -1;
+    virErrorPtr orig_err = NULL;
+    virDomainShmemDefPtr shmem = NULL;
+    qemuDomainObjPrivatePtr priv = vm->privateData;
+
+    if ((idx = virDomainShmemDefFind(vm->def, dev->data.shmem) < 0)) {
+        virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                       _("device not present in domain
configuration"));
+        return -1;
+    }
+
+    shmem = vm->def->shmems[idx];
+
+    switch ((virDomainShmemModel)shmem->model) {
+    case VIR_DOMAIN_SHMEM_MODEL_IVSHMEM_PLAIN:
+    case VIR_DOMAIN_SHMEM_MODEL_IVSHMEM_DOORBELL:
+        break;
+
+    case VIR_DOMAIN_SHMEM_MODEL_IVSHMEM:
+        virReportError(VIR_ERR_OPERATION_UNSUPPORTED,
+                       _("live detach of shmem model '%s' is not
supported"),
+                       virDomainShmemModelTypeToString(shmem->model));
+        /* fall-through */
+    case VIR_DOMAIN_SHMEM_MODEL_LAST:
+        return -1;
+    }
+
+    qemuDomainMarkDeviceForRemoval(vm, &shmem->info);
+    qemuDomainObjEnterMonitor(driver, vm);
+
+    ret = qemuMonitorDelDevice(priv->mon, shmem->info.alias);
+
+    if (ret < 0)
+        orig_err = virSaveLastError();
+
+    if (qemuDomainObjExitMonitor(driver, vm) < 0)
+        ret = -1;
+
+    if (ret == 0) {
+        if ((ret = qemuDomainWaitForDeviceRemoval(vm)) == 1) {
+            qemuDomainReleaseDeviceAddress(vm, &shmem->info, NULL);
+            ret = qemuDomainRemoveDevice(driver, vm, dev);

Why not a direct qemuDomainRemoveShmemDevice(driver, vm, shmem);

It's the pattern other code uses - just concern over the difference - it
does result in the same call eventually.


What other code?  It doesn't necessarily result in the same call every
time.  That's what qemuDomainWaitForDeviceRemoval() is for.  We
shouldn't remove it from the definition if QEMU didn't actually remove
it.


Most callers to qemuDomainWaitForDeviceRemoval except
qemuDomainDetachChrDevice which throws in release device address, but
still calls its RemoveChrDevice directly rather than the generic
RemoveDevice call.


Oh, I misunderstood that, you meant qemuDomainRemoveShmemDevice() instead
of qemuDomainRemoveDevice().  Yes, I can do that, I left the Device
there because I was using the actual device for something in one of the
versions before posting it and then haven't changed it back.

John

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