[libvirt] [PATCH v4 6/6] qemu: Add support for hot/cold-(un)plug of shmem devices

[Peter Krempa]

On Wed, Oct 26, 2016 at 12:51:37 +0200, Martin Kletzander wrote:
> This is needed in order to migrate a domain with shmem devices as that
> is not allowed to migrate.
> 
> Signed-off-by: Martin Kletzander <mkletzan at redhat.com>
> ---
>  src/qemu/qemu_driver.c                             |  39 +++-
>  src/qemu/qemu_hotplug.c                            | 248 ++++++++++++++++++++-
>  src/qemu/qemu_hotplug.h                            |   6 +
>  tests/qemuhotplugtest.c                            |  21 ++
>  .../qemuhotplug-ivshmem-doorbell-detach.xml        |   7 +
>  .../qemuhotplug-ivshmem-doorbell.xml               |   4 +
>  .../qemuhotplug-ivshmem-plain-detach.xml           |   6 +
>  .../qemuhotplug-ivshmem-plain.xml                  |   3 +
>  ...muhotplug-base-live+ivshmem-doorbell-detach.xml |   1 +
>  .../qemuhotplug-base-live+ivshmem-doorbell.xml     |  65 ++++++
>  .../qemuhotplug-base-live+ivshmem-plain-detach.xml |   1 +
>  .../qemuhotplug-base-live+ivshmem-plain.xml        |  58 +++++
>  12 files changed, 454 insertions(+), 5 deletions(-)
>  create mode 100644 tests/qemuhotplugtestdevices/qemuhotplug-ivshmem-doorbell-detach.xml
>  create mode 100644 tests/qemuhotplugtestdevices/qemuhotplug-ivshmem-doorbell.xml
>  create mode 100644 tests/qemuhotplugtestdevices/qemuhotplug-ivshmem-plain-detach.xml
>  create mode 100644 tests/qemuhotplugtestdevices/qemuhotplug-ivshmem-plain.xml
>  create mode 120000 tests/qemuhotplugtestdomains/qemuhotplug-base-live+ivshmem-doorbell-detach.xml
>  create mode 100644 tests/qemuhotplugtestdomains/qemuhotplug-base-live+ivshmem-doorbell.xml
>  create mode 120000 tests/qemuhotplugtestdomains/qemuhotplug-base-live+ivshmem-plain-detach.xml
>  create mode 100644 tests/qemuhotplugtestdomains/qemuhotplug-base-live+ivshmem-plain.xml
> 
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index bacabd2d348f..c164c390eccf 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -7601,6 +7601,15 @@ qemuDomainAttachDeviceLive(virDomainObjPtr vm,
>          dev->data.memory = NULL;
>          break;
> 
> +    case VIR_DOMAIN_DEVICE_SHMEM:
> +        ret = qemuDomainAttachShmemDevice(driver, vm,
> +                                          dev->data.shmem);
> +        if (!ret) {

Change the condition to something more orthodox, like "< 0".

> +            alias = dev->data.shmem->info.alias;
> +            dev->data.shmem = NULL;
> +        }
> +        break;
> +
>      case VIR_DOMAIN_DEVICE_NONE:
>      case VIR_DOMAIN_DEVICE_FS:
>      case VIR_DOMAIN_DEVICE_INPUT:

[...]


> diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c
> index 7a21dc67f533..10236a0bccd9 100644
> --- a/src/qemu/qemu_hotplug.c
> +++ b/src/qemu/qemu_hotplug.c

[...]

> @@ -4271,6 +4455,68 @@ int qemuDomainDetachHostDevice(virQEMUDriverPtr driver,
>          return qemuDomainDetachThisHostDevice(driver, vm, detach);
>  }
> 
> +
> +int
> +qemuDomainDetachShmemDevice(virQEMUDriverPtr driver,
> +                            virDomainObjPtr vm,
> +                            virDomainShmemDefPtr 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)) < 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();

Is this necessary? The only place where it would be overwritten is ...

> +
> +    if (qemuDomainObjExitMonitor(driver, vm) < 0)

... here and only if qemu crashes at this point.

> +        ret = -1;
> +
> +    if (ret == 0) {
> +        if ((ret = qemuDomainWaitForDeviceRemoval(vm)) == 1) {
> +            qemuDomainReleaseDeviceAddress(vm, &shmem->info, NULL);
> +            ret = qemuDomainRemoveShmemDevice(driver, vm, shmem);
> +        }
> +    }
> +    qemuDomainResetDeviceRemoval(vm);
> +
> +    if (orig_err) {
> +        virSetError(orig_err);
> +        virFreeError(orig_err);
> +    }

ACK
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