Date:   Mon, 11 Oct 2021 18:00:16 -0700
From:   Russ Weight <russell.h.weight@...el.com>
To:     Tom Rix <trix@...hat.com>, Xu Yilun <yilun.xu@...el.com>
CC:     <mdf@...nel.org>, <linux-fpga@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <lgoncalv@...hat.com>,
        <hao.wu@...el.com>, <matthew.gerlach@...el.com>
Subject: Re: [PATCH v17 0/5] FPGA Image Load (previously Security Manager)



On 10/11/21 5:35 AM, Tom Rix wrote:
>
> On 10/10/21 6:41 PM, Xu Yilun wrote:
>> On Sat, Oct 09, 2021 at 05:11:20AM -0700, Tom Rix wrote:
>>> On 10/9/21 1:08 AM, Xu Yilun wrote:
>>>> On Wed, Sep 29, 2021 at 04:00:20PM -0700, Russ Weight wrote:
>>>>> The FPGA Image Load framework provides an API to upload image
>>>>> files to an FPGA device. Image files are self-describing. They could
>>>>> contain FPGA images, BMC images, Root Entry Hashes, or other device
>>>>> specific files. It is up to the lower-level device driver and the
>>>>> target device to authenticate and disposition the file data.
>>>> I've reconsider the FPGA persistent image update again, and think we
>>>> may include it in FPGA manager framework.
>>>>
>>>> Sorry I raised this topic again when it is already at patch v17, but now
>>>> I need to consider more seriously than before.
>>>>
>>>> We have consensus the FPGA persistent image update is just like a normal
>>>> firmware update which finally writes the nvmem like flash or eeprom,
>>>> while the current FPGA manager deals with the active FPGA region update
>>>> and re-activation. Could we just expand the FPGA manager and let it handle
>>>> the nvmem update as well? Many FPGA cards have nvmem and downloaders
>>>> supports updating both FPGA region and nvmem.
The fpga-image-load driver is actually just a data transfer. The class
driver has no knowledge about what the data is or where/if the data will
be stored.

This functionality could, of course, be merged into the fpga-mgr. I did
a proof of concept of this a while back and we discussed the pros and cons.
See this email for a recap:

https://marc.info/?l=linux-fpga&m=161998085507374&w=2

Things have changed some with the evolution of the driver. The IOCTL
approach probably fits better than the sysfs implementation. At the time
it seemed that a merge would add unnecessary complexity without adding value.

>>>>
>>>> According to the patchset, the basic workflow of the 2 update types are
>>>> quite similar, get the data, prepare for the HW, write and complete.
>>>> They are already implemented in FPGA manager. We've discussed some
>>>> differences like threading or canceling the update, which are
>>>> not provided by FPGA manager but they may also nice to have for FPGA
>>>> region update. An FPGA region update may also last for a long time??
>>>> So I think having 2 sets of similar frameworks in FPGA is unnecessary.
>>>>
>>>> My quick mind is that we add some flags in struct fpga_mgr & struct
>>>> fpga_image_info to indicate the HW capability (support FPGA region
>>>> update or nvmem update or both) of the download engine and the provided
>>>> image type. Then the low-level driver knows how to download if it
>>>> supports both image types.An char device could be added for each fpga manager dev, providing the
>>>> user APIs for nvmem update. We may not use the char dev for FPGA region
>>>> update cause it changes the system HW devices and needs device hotplug
>>>> in FPGA region. We'd better leave it to FPGA region class, this is
>>>> another topic.
I'll give this some more thought and see if I can come up with some RFC
patches.

- Russ
>>>>
>>>> More discussion is appreciated.
>>> I also think fpga_mgr could be extended.
>>>
>>> In this patchset,
>>>
>>> https://lore.kernel.org/linux-fpga/20210625195849.837976-1-trix@redhat.com/
>>>
>>> A second, similar set of write ops was added to fpga_manger_ops,
>>>
>>> new bit/flag was added to fpga_image_info
>>>
>>> The intent was for dfl to add their specific ops to cover what is done in
>>> this patchset.
>> I think we don't have to add 2 ops for reconfig & reimage in framework,
>> the 2 processes are almost the same.
>>
>> Just add the _REIMAGE (or something else, NVMEM?) flag for
>> fpga_image_info, and low level drivers handle it as they do for other
>> flags.
>>
>> How do you think?
>
> A single set is fine.
>
> A difficult part of is the length of  time to do the write. The existing write should be improved to use a worker thread.
>
> Tom
>
>>
>> Thanks,
>> Yilun
>>
>>> Any other driver would do similar.
>>>
>>> Is this close to what you are thinking ?
>>>
>>> Tom
>>>
>>>> Thanks,
>>>> Yilun
>>>>
>

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