[dpdk-dev] Query : Does Binding with vfio-pci is supported inside qemu-kvm guest/vm instance.?

[Burakov, Anatoly]

On 12-Mar-19 10:20 AM, Bruce Richardson wrote:
> On Tue, Mar 12, 2019 at 05:54:39PM +0800, Jason Wang wrote:
>>
>> On 2019/3/12 下午5:42, Thanneeru Srinivasulu wrote:
>>> Thanks Bruce..
>>>
>>> On Tue, Mar 12, 2019 at 3:08 PM Bruce Richardson
>>> <bruce.richardson at intel.com> wrote:
>>>> On Tue, Mar 12, 2019 at 10:57:55AM +0530, Thanneeru Srinivasulu wrote:
>>>>> Hi Everyone.
>>>>>
>>>>> I did attached pice  to Guest VM using vfio-pci with qemu command, and then
>>>>> tried binding the pcie bdf with vfio-pci, observing binding failure with
>>>>> vfio-pci.
>>>>>
>>>>> Where as when tryied with igb_uio, everything works fine.
>>>>>
>>>>> Does Binding with vfio-pci is supported inside VM/guest?
>>>>>
>>>> vfio support requires the presence of an IOMMU, and you generally don't
>>>> have an IOMMU available in a VM.
>>>>
>>>> /Bruce
>>
>>
>> Actually, Qemu support vIOMMU + VFIO in guest[1], all you need is to add a
>> intel IOMMU and enabling caching mode.
>>
>> Thanks
>>
>>
>> [1]
>>
>> https://www.lfasiallc.com/wp-content/uploads/2017/11/Device-Assignment-with-Nested-Guests-and-DPDK_Peter-Xu.pdf
>>
> Thanks for the info.
> 
> /Bruce
> 

One more thing: even without vIOMMU, VFIO has no-IOMMU mode which can be 
enabled (for a recent-enough kernel). This will make VFIO work even in 
cases where the guest doesn't have IOMMU emulation. See? There's no 
reason to use igb_uio, ever! :D

-- 
Thanks,
Anatoly