[libvirt] [PATCH 7/8 v8] qemu: Set unpriv_sgio when attaching disk

[Osier Yang]

On 2012年12月15日 06:05, Eric Blake wrote:
> On 12/14/2012 08:45 AM, Osier Yang wrote:
>> Just like for domain starting, this sets the disk's unpriv_sgio
>> if cdbfilter is specified when attaching disk.
>> ---
>>   src/qemu/qemu_driver.c |   23 +++++++++++++++++------
>>   1 files changed, 17 insertions(+), 6 deletions(-)
>
>> +
>> +        /* Set sysfs unpriv_sgio if cdbfilter is specified. */
>> +        if (disk->cdbfilter) {
>> +            if (virSetDeviceUnprivSGIO(disk->src, NULL,
>> +                                       (disk->cdbfilter ==
>> +                                       VIR_DOMAIN_DISK_CDB_FILTER_NO)
>> +                                       ? 1 : 0)<  0) {
>> +                VIR_WARN("Failed to set unpriv_sgio of disk '%s'", disk->src);
>> +                goto end;
>> +            }
>> +        }
>
> Again, does this do the right thing if some other domain already had
> cdbfilter='no' (aka kernel allows SG_IO) but this domain omitted the
> cdbfilter attribute (which defaults to cdbfilter='yes' but does not
> satisfy the if(disk->cdbfilter) condition)?

I think it does the right thing, because not specifying "cdbfilter"
should mean it doesn't care about what the kernel setting is, not
means cdbfiler="yes" instead. Assuming that one used rawio="yes"
for a domain, and if we defaults cdbfilter to "yes", it will cause
regression, as the user still expects SG_IO commands can be executed
on the disk, however, it's disabled by cdbfilter="yes".


>  I suspect that will be
> worked out when you rework things to use a tri-state rawio.

Of course, this is based on we use a separate XML tag like cdbfilter,
it won't stand anymore if we finally use a tri-state rawio.

Regards,
Osier