Ian Campbell wrote:
>> if (l_disk->driverName) {
>> ...
>> } else {
>> /* No driverName - default to raw/tap?? */
>> x_disk->format = LIBXL_DISK_FORMAT_RAW;
>> x_disk->backend = LIBXL_DISK_BACKEND_TAP;
>> }
>>
>> I recall some discussion about the choice of these defaults, but can't
>> find anything in the xen or libvirt ml archives. We can adjust the
>> defaults (or defer to libxl?) if it makes sense. I took a quick peek at
>> newer libxl code (recall this was written against Xen 4.1 libxl) and
>> perhaps 'x_disk->backend = LIBXL_DISK_BACKEND_QDISK' would be a saner
>> default? Adding Ian to help with this question...
>>
>
> LIBXL_DISK_BACKEND_UNKNOWN will cause libxl to pick the best available
> (which includes checking if blktap is actually there) backend given the
> format and file type (block device, file etc). That's probably the right
> default.
>
Ok, thanks.
> libxl__device_disk_set_backend is the guy to look at if you are
> interested how the selection happens.
>
After taking a peek, agreed that LIBXL_DISK_BACKEND_UNKNOWN is a better
backend default. I'll leave the format default of LIBXL_DISK_FORMAT_RAW
to be consistent with $xen-src/docs/misc/xl-disk-configuration.txt.
Thanks,
Jim
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