[libvirt] [PATCH 0/4] qemu_hotplug: Check for duplicate drive addresses

[Michal Privoznik]

On 4/11/19 8:36 PM, Daniel Henrique Barboza wrote:
> 
> 
> On 4/11/19 11:34 AM, Michal Privoznik wrote:
>> This is an alternative approach to:
>>
>> https://www.redhat.com/archives/libvir-list/2019-March/msg01111.html
>>
>> which caused regression to which a proposed fix is here:
>>
>> https://www.redhat.com/archives/libvir-list/2019-April/msg00756.html
>>
>> One of the selling points was that having this check in
>> virDomainDefCompatibleDevice() will fix the problem across all drivers.
>> Well, turns out, some drivers don't care (e.g. lxc) and some have a
>> different workflow and thus don't need that check.
> 
> Just tested the patch series and it fixes the problem for SCSI disks, as
> expected.
> 
> The major drawback of reverting that patch is that we lose the address
> check not just for other drivers (that might not care much for that), but
> also for the remaining device types other than SCSI disks.
> 
> Now, taking a quick look in the code I see that there are similar checks
> being made in VDA, PCI and DIMM type devices (didn't check the remaining
> devices). If there are address redundancy checks for all other devices, 
> then
> the patch can be reverted without loss.

Yep, other types of addresees are covered. At least in drivers that do 
care. LXC doesn't because it doesn't make much sense there. I mean, a 
container shares HW with the host, so we can't really make it appear at 
different addresses. For instance, when plugging a disk into an LXC 
container it'll appear at the same adddess as in the host and no 
<address/> in the XML is going to change that.

That's why I vouche for this approach. Sorry for not realizing this the 
first time.

> 
> It is worth mentioning that the first 2 patches can be applied 
> regardless of
> what it is decided to do about the address checking, since they are a 
> straight
> improvement in what already exists.

Thanks,

Michal