[PATCH v6 2/8] qemu_driver: Probe capability before calculating dirty page rate

[Michal Prívozník]

On 2/20/22 14:28, huangy81 at chinatelecom.cn wrote:
> From: Hyman Huang(黄勇) <huangy81 at chinatelecom.cn>
> 
> Probing QEMU_CAPS_CALC_DIRTY_RATE capability in advance
> in case of failure when calculating dirty page rate.
> 
> Signed-off-by: Hyman Huang(黄勇) <huangy81 at chinatelecom.cn>
> ---
>  src/qemu/qemu_driver.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index f1f708e..9b50f5f 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -20693,6 +20693,13 @@ qemuDomainStartDirtyRateCalc(virDomainPtr dom,
>      if (virDomainStartDirtyRateCalcEnsureACL(dom->conn, vm->def) < 0)
>          goto cleanup;
>  
> +    priv = vm->privateData;
> +    if (!virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_CALC_DIRTY_RATE)) {
> +        virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
> +                       _("QEMU does not support calculating dirty page rate"));
> +        goto cleanup;
> +    }
> +

Sorry for not telling you the whole truth. priv->qemuCaps is populated
only when domain is running. Therefore for inactive domains this ^^^
error message is reported which may be a bit misleading. But the fix is
trivial, just check whether domain is active before querying priv-qemuCaps.

>      if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
>          goto cleanup;
>  
> @@ -20704,7 +20711,6 @@ qemuDomainStartDirtyRateCalc(virDomainPtr dom,
>  
>      VIR_DEBUG("Calculate dirty rate in next %d seconds", seconds);
>  
> -    priv = vm->privateData;
>      qemuDomainObjEnterMonitor(driver, vm);
>      ret = qemuMonitorStartDirtyRateCalc(priv->mon, seconds);
>  

Michal