[libvirt] [PATCH libvirt] qemu: show a warning when using aio=native without cache=none

[Giuseppe Scrivano]

"Daniel P. Berrange" <berrange at redhat.com> writes:

> On Tue, Jul 08, 2014 at 02:08:38PM +0200, Giuseppe Scrivano wrote:
>> Qemu will fallback to aio=threads when the cache mode doesn't use
>> O_DIRECT, even if aio=native was explictly set.
>> 
>> Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1086704
>> 
>> Signed-off-by: Giuseppe Scrivano <gscrivan at redhat.com>
>> ---
>>  src/qemu/qemu_command.c | 7 +++++++
>>  1 file changed, 7 insertions(+)
>> 
>> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
>> index fb64cda..92a6c9a 100644
>> --- a/src/qemu/qemu_command.c
>> +++ b/src/qemu/qemu_command.c
>> @@ -3477,6 +3477,13 @@ qemuBuildDriveStr(virConnectPtr conn,
>>              mode = qemuDiskCacheV1TypeToString(disk->cachemode);
>>          }
>>  
>> +        if (disk->iomode == VIR_DOMAIN_DISK_IO_NATIVE &&
>> +            disk->cachemode != VIR_DOMAIN_DISK_CACHE_DIRECTSYNC) {
>> +            VIR_WARN("native I/O needs either no disk cache "
>> +                     "or directsync cache mode, QEMU will fallback "
>> +                     "to aio=threads");
>> +        }
>
> VIR_WARN is not really appropriate for warning about things that
> are client application mistakes. If this combination of options
> does not work or is not supported then we should report an
> error about this.

I didn't want to block the VM execution as anyway qemu allows this
combination.  I will change it to use virReportError.

Thanks,
Giuseppe