[libvirt] [PATCHv6 1/5] Add a hostdev PCI backend type

Jim Fehlig jfehlig at suse.com
Tue Nov 26 02:09:04 UTC 2013


Laine Stump wrote:
> On 11/22/2013 11:08 PM, Jim Fehlig wrote:
>   
>> Chunyan Liu wrote:
>>     
>>> Add VIR_DOMAIN_HOSTDEV_PCI_BACKEND_XEN. For legacy xen, it will use "pciback" as
>>> stub driver.
>>>   
>>>       
>> Sorry for the long delay in helping review these patches. I finally have
>> some time to work on libvirt :).
>>
>> With the pending release, this series will have to wait for the next
>> cycle, but hopefully we can get it in early for prolonged testing. It
>> plugs a big hole in the libxl dirver, so thanks for your work and
>> perseverance :).
>>
>> I've applied your patches to latest git master and testing looks good so
>> far, after fixing a small issue in 2/5. See the individual patches for
>> further comments.
>>     
>
> The part that has made me nervous about this series from the beginning
> is that it is moving the implementation of some pretty hairy code from
> qemu-specific to a general library while that code has itself been
> getting fairly frequently bugfix tweaks.

When Chunyan originally submitted the patch adding PCI passthrough
support in the libxl driver, it was noted that a lot of the code is not
qemu-specific, based on the amount of copy-and-paste, and hence the
request for common code :-). Do you think a lot of the bugs in this code
are specific to the qemu driver? I don't have a feel for the number of
common vs hypervisor-specific bugs.

>  Fortunately we now have several
> more unit tests on this code, but before pushing we still should do a
> bit of extra due diligence to make sure that no recent bugfixes to the
> qemu-specific version of the code are missing in the new versions.

Agreed. I'd suggest unit tests for the virhostdev interface introduced
in 2/5.

Chunyan, tests/virpcitest.c should provide some ideas for virhostdev
unit tests.

>  (BTW,
> for this reason I think it is a very good idea to switch qemu and lxc
> over to this new library immediately, rather than waiting as was done in
> an earlier version of the patch series.)

I think her original post was only an RFC to get consensus on a
virhostdev interface, one which hopefully prevents hypervisor-specific
code from trickling into the common code. But definitely agree that the
qemu and lxc drivers should switch immediately.

Regards,
Jim




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