On 12/14/2013 07:15 PM, Cole Robinson wrote:
> On 12/11/2013 03:33 PM, Michele Paolino wrote:
>> In libvirt, the default error message length is 1024 bytes. This is not
>> enough for qemu to print long error messages such as the list of
>> supported ARM machine models (more than 1700 chars). This is
>> raised when the machine entry in the XML file is wrong, but there may
>> be now or in future other verbose error messages.
>> The above patch enables libvirt to print error messages >1024 for qemu.
>>
>> Signed-off-by: Michele Paolino <m.paolino@xxxxxxxxxxxxxxxxxxxxxx>
>> ---
>> src/qemu/qemu_process.c | 23 +++++++++++++++++++----
>> 1 file changed, 19 insertions(+), 4 deletions(-)
>>
>> diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
>> index bd9546e..c2e2136 100644
>> --- a/src/qemu/qemu_process.c
>> +++ b/src/qemu/qemu_process.c
>> @@ -1904,10 +1904,25 @@ cleanup:
>> * a possible read of the fd in the monitor code doesn't influence this
>> * error delivery option */
>> ignore_value(lseek(logfd, pos, SEEK_SET));
>> - qemuProcessReadLog(logfd, buf + len, buf_size - len - 1, 0, true);
>> - virReportError(VIR_ERR_INTERNAL_ERROR,
>> - _("process exited while connecting to monitor: %s"),
>> - buf);
>> + len = qemuProcessReadLog(logfd, buf + len, buf_size - len - 1, 0, true);
>> +
>> + /* virReportError error buffer is limited to 1024 byte*/
>> + if (len < 1024){
>> + virReportError(VIR_ERR_INTERNAL_ERROR,
>> + _("process exited while connecting to monitor: %s"),
>> + buf);
>> + } else {
>> + if (STRPREFIX(buf, "Supported machines are:"))
>> + virReportError(VIR_ERR_INTERNAL_ERROR,
>> + _("process exited while connecting to monitor:"
>> + "please check machine model"));
>> + else
>> + virReportError(VIR_ERR_INTERNAL_ERROR,
>> + _("process exited while connecting to monitor"));
>> +
>> + VIR_ERROR("%s", buf);
>> + }
>> +
>> ret = -1;
>> }
>>
>>
> This kind of error scraping is a slipper slop IMO, and for this particular
> case I don't think it's even that interesting.
I definitely agree with that.
>
> Libvirt already parses the machine types for each qemu emulator and reports it
> in virsh capabilities XML. Seems reasonable that we could validate the XML
> machine type at define time and catch an invalid machine type error long
> before we even try and start the VM.
Do we really want to refuse to define a particular guest just because
the host where we're defining it doesn't currently support the given
machine type? That's yet another slippery slope - for example, should we
also be validating all the devices in <hostdev> at definition time? I
think the proper time to do that validation is at domain start time when
we should have the proper qemu binary (and necessary drivers/hardware)
available.
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