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

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 02-Apr-19 11:38 AM, John Sucaet wrote:
> Hi Anatoly,
> 
> As you said: There's no reason to use igb_uio, ever!

That was partly tongue in cheek, but point taken :)

> I would like to ask whether vfio-pci with or without vIOMMU should/could 
> work for virtio-pci net devices in the case of a 32-bit dpdk 
> application, on a 64-bit kernel (4.9) inside a guest VM 
> (qemu-2.10.2-1.fc27)?
> 
> I tried both a 64-bit and a 32-bit version of the same application, but 
> only in the case of the 64-bit application, the port was found by eal. 
> The 32-bit application gave errors like:
> 
> EAL: pci_map_resource(): cannot mmap(16, 0xf4a01000, 0x4000, 0x0): 
> Invalid argument (0xffffffff)
> EAL: Failed to map pci BAR4
> EAL:   0000:00:02.0 mapping BAR4 failed: Invalid argument
> EAL: Can't write to PCI bar (0) : offset (12)
> EAL: Can't read from PCI bar (0) : offset (12)
> EAL: Can't read from PCI bar (0) : offset (12)
> EAL: Can't write to PCI bar (0) : offset (12)
> EAL: Can't read from PCI bar (0) : offset (12)
> EAL: Can't write to PCI bar (0) : offset (12)
> EAL: Can't read from PCI bar (0) : offset (0)
> EAL: Can't write to PCI bar (0) : offset (4)
> EAL: Can't write to PCI bar (0) : offset (14)
> EAL: Can't read from PCI bar (0) : offset (14)
> EAL: Can't read from PCI bar (0) : offset (1a)
> EAL: Can't read from PCI bar (0) : offset (1c)
> EAL: Can't write to PCI bar (0) : offset (e)
> EAL: Can't read from PCI bar (0) : offset (c)
> virtio_init_queue(): virtqueue size is not powerof 2
> EAL: Requested device 0000:00:02.0 cannot be used
> 
> Maybe you have an idea what went wrong here?
> 
> By preference, I would like to continue to use the 32-bit application 
> which worked fine with the igb_uio driver.

Unfortunately, i am not very familiar with virtio and wouldn't know 
whether it's supposed to work under these conditions. Perhaps Maxime 
would be of more help here (CC'd).

> 
> 
> Thanks
> 
> John
> 
> 
> On 03/12/2019 11:57 AM, Burakov, Anatoly wrote:
>> 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@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