[libvirt] [PATCH 06/11] qemu: Add monitor functions to set IOThread params

[Michal Privoznik]

On 10/07/2018 03:00 PM, John Ferlan wrote:
> Add functions to set the IOThreadInfo param data for the live guest.
> 
> Based on code originally posted by Pavel Hrdina <phrdina at redhat.com>,
> but extracted into a separate patch. Note that qapi expects to receive
> integer parameters rather than unsigned long long or unsigned int's.
> QEMU does save the value in larger signed 64 bit values eventually.
> 
> Signed-off-by: John Ferlan <jferlan at redhat.com>
> ---
>  src/qemu/qemu_monitor.c      | 19 +++++++++++++++++++
>  src/qemu/qemu_monitor.h      |  2 ++
>  src/qemu/qemu_monitor_json.c | 33 +++++++++++++++++++++++++++++++++
>  src/qemu/qemu_monitor_json.h |  4 ++++
>  4 files changed, 58 insertions(+)
> 
> diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
> index 7f7013e115..a65d638ab8 100644
> --- a/src/qemu/qemu_monitor.c
> +++ b/src/qemu/qemu_monitor.c
> @@ -4135,6 +4135,25 @@ qemuMonitorGetIOThreads(qemuMonitorPtr mon,
>  }
>  
>  
> +/**
> + * qemuMonitorSetIOThread:
> + * @mon: Pointer to the monitor
> + * @iothreadInfo: filled IOThread info with data
> + *
> + * Alter the specified IOThread's IOThreadInfo values.
> + */
> +int
> +qemuMonitorSetIOThread(qemuMonitorPtr mon,
> +                       qemuMonitorIOThreadInfoPtr iothreadInfo)
> +{
> +    VIR_DEBUG("iothread=%p", iothreadInfo);
> +
> +    QEMU_CHECK_MONITOR(mon);
> +
> +    return qemuMonitorJSONSetIOThread(mon, iothreadInfo);
> +}
> +
> +
>  /**
>   * qemuMonitorGetMemoryDeviceInfo:
>   * @mon: pointer to the monitor
> diff --git a/src/qemu/qemu_monitor.h b/src/qemu/qemu_monitor.h
> index c2991e2b16..ef71fc6448 100644
> --- a/src/qemu/qemu_monitor.h
> +++ b/src/qemu/qemu_monitor.h
> @@ -1123,6 +1123,8 @@ struct _qemuMonitorIOThreadInfo {
>  };
>  int qemuMonitorGetIOThreads(qemuMonitorPtr mon,
>                              qemuMonitorIOThreadInfoPtr **iothreads);
> +int qemuMonitorSetIOThread(qemuMonitorPtr mon,
> +                           qemuMonitorIOThreadInfoPtr iothreadInfo);
>  
>  typedef struct _qemuMonitorMemoryDeviceInfo qemuMonitorMemoryDeviceInfo;
>  typedef qemuMonitorMemoryDeviceInfo *qemuMonitorMemoryDeviceInfoPtr;
> diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
> index 2e92984b44..bb1d62b844 100644
> --- a/src/qemu/qemu_monitor_json.c
> +++ b/src/qemu/qemu_monitor_json.c
> @@ -7474,6 +7474,39 @@ qemuMonitorJSONGetIOThreads(qemuMonitorPtr mon,
>  }
>  
>  
> +int
> +qemuMonitorJSONSetIOThread(qemuMonitorPtr mon,
> +                           qemuMonitorIOThreadInfoPtr iothreadInfo)
> +{
> +    int ret = -1;
> +    char *path = NULL;
> +    qemuMonitorJSONObjectProperty prop;
> +
> +    if (virAsprintf(&path, "/objects/iothread%u",
> +                    iothreadInfo->iothread_id) < 0)
> +        goto cleanup;
> +
> +#define VIR_IOTHREAD_SET_PROP(propName, propVal) \
> +    memset(&prop, 0, sizeof(qemuMonitorJSONObjectProperty)); \
> +    prop.type = QEMU_MONITOR_OBJECT_PROPERTY_INT; \
> +    prop.val.iv = propVal; \
> +    if (qemuMonitorJSONSetObjectProperty(mon, path, propName, &prop) < 0) \
> +        goto cleanup;
> +
> +    VIR_IOTHREAD_SET_PROP("poll-max-ns", iothreadInfo->poll_max_ns)
> +    VIR_IOTHREAD_SET_PROP("poll-grow", iothreadInfo->poll_grow)
> +    VIR_IOTHREAD_SET_PROP("poll-shrink", iothreadInfo->poll_shrink)

So this is all or nothing approach. All values are set - even though
user might request through public API to change just one. I don't think
it is a good design. Either we need a monitor API that changes just one
value and call it for every typed parameter that user sends to us, or
public API implementation must copy the old values into this struct
(even though it would be ugly).

Michal