Re: live migration vs device assignment (motivation)

["Lan, Tianyu" <tianyu.lan@intel.com>]

On 12/10/2015 1:14 AM, Alexander Duyck wrote:
> On Wed, Dec 9, 2015 at 8:26 AM, Lan, Tianyu <tianyu.lan@intel.com> wrote:
>
>> For other kind of devices, it's hard to work.
>> We are also adding migration support for QAT(QuickAssist Technology) device.
>>
>> QAT device user case introduction.
>> Server, networking, big data, and storage applications use QuickAssist
>> Technology to offload servers from handling compute-intensive operations,
>> such as:
>> 1) Symmetric cryptography functions including cipher operations and
>> authentication operations
>> 2) Public key functions including RSA, Diffie-Hellman, and elliptic curve
>> cryptography
>> 3) Compression and decompression functions including DEFLATE and LZS
>>
>> PCI hotplug will not work for such devices during migration and these
>> operations will fail when unplug device.
>
> I assume the problem is that with a PCI hotplug event you are losing
> the state information for the device, do I have that right?
>
> Looking over the QAT drivers it doesn't seem like any of them support
> the suspend/resume PM calls.  I would imagine it makes it difficult
> for a system with a QAT card in it to be able to drop the system to a
> low power state.  You might want to try enabling suspend/resume
> support for the devices on bare metal before you attempt to take on
> migration as it would provide you with a good testing framework to see
> what needs to be saved/restored within the device and in what order
> before you attempt to do the same while migrating from one system to
> another.

Sure. The suspend/resume job is under way.
Actually, we have enabled QAT work for migration internally. Doing more 
test and fixing bugs.

>
> - Alex
>