Re: [dpdk-dev] [PATCH v13 2/2] eal: support for VFIO-PCI VF token

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 5/6/20 7:56 PM, Wang, Haiyue wrote:
>> -----Original Message-----
>> From: Andrew Rybchenko <arybchenko@solarflare.com>
>> Sent: Thursday, May 7, 2020 00:51
>> To: Wang, Haiyue <haiyue.wang@intel.com>; dev@dpdk.org; Burakov, Anatoly <anatoly.burakov@intel.com>;
>> thomas@monjalon.net; jerinj@marvell.com; david.marchand@redhat.com
>> Subject: Re: [dpdk-dev] [PATCH v13 2/2] eal: support for VFIO-PCI VF token
>>
>> On 5/6/20 2:35 PM, Haiyue Wang wrote:
>>> The kernel module vfio-pci introduces the VF token to enable SR-IOV
>>> support since 5.7.
>>>
>>> The VF token can be set by a vfio-pci based PF driver and must be known
>>> by the vfio-pci based VF driver in order to gain access to the device.
>>>
>>> Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
>>> Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>
>>
>> Sorry, lost from my view new versions of the patch series.
>>
>> Acked-by: Andrew Rybchenko <arybchenko@solarflare.com>
>>
>>> diff --git a/doc/guides/linux_gsg/linux_drivers.rst b/doc/guides/linux_gsg/linux_drivers.rst
>>> index 238f3e900..910397243 100644
>>> --- a/doc/guides/linux_gsg/linux_drivers.rst
>>> +++ b/doc/guides/linux_gsg/linux_drivers.rst
>>> @@ -72,11 +72,44 @@ Note that in order to use VFIO, your kernel must support it.
>>>  VFIO kernel modules have been included in the Linux kernel since version 3.6.0 and are usually
>> present by default,
>>>  however please consult your distributions documentation to make sure that is the case.
>>>
>>> +The ``vfio-pci`` module since Linux version 5.7 supports the creation of virtual
>>> +functions. After the PF is bound to vfio-pci module, the user can create the VFs
>>> +by sysfs interface, and these VFs are bound to vfio-pci module automatically.
>>> +
>>> +When the PF is bound to vfio-pci, it has initial VF token generated by random. For
>>> +security reason, this token is write only, the user can't read it from the kernel
>>> +directly. For accessing the VF, the user needs to start the PF with token parameter
>>> +to setup a VF token (uuid format), then the VF can be accessed with this new known
>>> +VF token.
>>
>> If token is write-only in kernel sysfs, shouldn't we make it
>> invisible in ps output? I.e. substitute with something like
>> xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx.
>> It is a bit easier with the new design. Just a thought.
>>
> 
> In fact, no sysfs for VF token, just write-only IOCTL. ;-)

OK, got it. The question remains anyway. Should it be treated
as a secret with at least minimal security precaution?