Message-ID: <e629eca0-a86c-4028-7bbf-65185699137b@intel.com>
Date:   Tue, 12 Oct 2021 10:20:15 -0700
From:   Russ Weight <russell.h.weight@...el.com>
To:     Xu Yilun <yilun.xu@...el.com>
CC:     Tom Rix <trix@...hat.com>, <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 10/12/21 12:47 AM, Xu Yilun wrote:
> On Mon, Oct 11, 2021 at 06:00:16PM -0700, Russ Weight wrote:
>>
>> 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
> IMHO, The fpga-mgr dev is also a data transfer. The fpga-region dev is
> acting as the FPGA region admin responsible for gating, transfering and
> re-enumerating.
>
> So my opinion is to add a new data transfer type and keep a unified process.
>
>> driver has no knowledge about what the data is or where/if the data will
>> be stored.
> The fpga-image-load driver knows the data will be stored in nvmem,
FYI: This is not strictly correct. In a coming product there is a
case where the data will be stored in RAM. Richard Gong was also
looking to use this driver to validate an image without programming
or storing it. The fpga-image-load driver has no expectation that
the data will be stored in nvmem, or even that it will be stored
at all.

> while
> the fpga-mgr knows the data will be stored in FPGA cells. They may need
> to know the exact physical position to store, may not, depends on what the
> HW engines are.
>
>> 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.
> I think at least developers don't have to go through 2 sets of software
> stacks which are of the same concept. And adding some new features like
> optionally threading or canceling data transfer are also good to FPGA
> region update. And the nvmem update could also be benifit from exsiting
> implementations like scatter-gather buffers, in-kernel firmware loading.
>
> I try to explain myself according to each of your concern from that mail
> thread:
>
> Purpose of the 2 updates
> ========================
>
>   As I said before, I think they are both data transfer devices. FPGA
> region update gets extra support from fpga-region & fpga-bridge, and
> FPGA nvmem update could be a standalone fpga-mgr.
>
> Extra APIs that are unique to nvmem update
> ==========================================
>
>   cdev APIs for nvmem update:
>     Yes we need to expand the functionality so we need them.
>
>   available_images, image_load APIs for loading nvmem content to FPGA
>   region:
>     These are features in later patchsets which are not submitted, but we
>     could talk about it in advance. I think this is actually a FPGA region
>     update from nvmem, it also requires gating, data loading (no SW transfer)
>     and re-enumeration, or a single command to image_load HW may result system
>     disordered. The FPGA framework now only supports update from in-kernel
>     user data, maybe we add support for update from nvmem later.
>
>   fpga-mgr state extend:
>     I think it could be extended, The current states are not perfect,
>     adding something like IDLE or READY is just fine.
>
>   fpga-mgr status extend:
>     Add general error definitions as needed. If there is some status
>     that is quite vendor specific, expose it in low-level driver.
>
>   remaining-size:
>     Nice to have for all.
>
> Threading the update
> ====================
>
>   Also a good option for FPGA region update, maybe we also have a slow FPGA
>   reprogrammer?
>
> Cancelling the update
> ====================
>
>   Also a good option for FPGA region update if HW engine supports.
These are all good points.

Thanks,
- Russ
>
> Thanks,
> Yilun
>
>>>>>> 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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