[PATCH v2 08/15] qemu_validate: Check if QEMU's capable of setting iothread pool size

[Peter Krempa]

On Tue, Jun 07, 2022 at 14:52:52 +0200, Michal Privoznik wrote:
> Now that we have a capability that reflects whether QEMU is
> capable of setting iothread pool size, let's introduce a
> validator check to make sure users are not trying to use this
> feature with QEMU that doesn't support it.
> 
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> Reviewed-by: Peter Krempa <pkrempa at redhat.com>
> ---
>  src/qemu/qemu_validate.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/src/qemu/qemu_validate.c b/src/qemu/qemu_validate.c
> index 9b6245e6d7..7d11ae2c92 100644
> --- a/src/qemu/qemu_validate.c
> +++ b/src/qemu/qemu_validate.c
> @@ -384,6 +384,27 @@ qemuValidateDomainDefCpu(virQEMUDriver *driver,
>  }
>  
>  
> +static int
> +qemuValidateDomainDefIOThreads(const virDomainDef *def,
> +                               virQEMUCaps *qemuCaps)
> +{
> +    size_t i;
> +
> +    for (i = 0; i < def->niothreadids; i++) {
> +        virDomainIOThreadIDDef *iothread = def->iothreadids[i];
> +
> +        if ((iothread->thread_pool_min != -1 || iothread->thread_pool_max != -1) &&
> +            !virQEMUCapsGet(qemuCaps, QEMU_CAPS_IOTHREAD_THREAD_POOL_MAX)) {
> +            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> +                           _("thread_pool_min and thread_pool_max is not supported by this QEMU binary"));
> +            return -1;
> +        }

You'll also need a check that 'thread_pool_max', if supplied, must be
more or equal to 'thread_pool_min', otherwise:

 $ virsh dumpxml cd | grep thread_pool
     <iothread id='3' thread_pool_min='4' thread_pool_max='3'/>
 $ virsh start cd
 error: Failed to start domain 'cd'
 error: internal error: process exited while connecting to monitor: 2022-06-07T14:58:52.420554Z qemu-system-x86_64: bad thread-pool-min/thread-pool-max values