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Date:   Wed, 20 Oct 2021 09:27:17 -0700
From:   Russ Weight <>
To:     Xu Yilun <>
CC:     Tom Rix <>, <>,
        <>, <>,
        <>, <>,
Subject: Re: [PATCH v17 0/5] FPGA Image Load (previously Security Manager)

On 10/19/21 6:16 PM, Xu Yilun wrote:
> On Tue, Oct 19, 2021 at 08:09:46AM -0700, Russ Weight wrote:
>> On 10/18/21 7:53 PM, Xu Yilun wrote:
>>> On Mon, Oct 18, 2021 at 09:24:08AM -0700, Russ Weight wrote:
>>>> On 10/18/21 1:13 AM, Xu Yilun wrote:
>>>>> On Fri, Oct 15, 2021 at 10:34:23AM -0700, Russ Weight wrote:
>>>>>> On 10/14/21 7:51 PM, Xu Yilun wrote:
>>>>>>> On Thu, Oct 14, 2021 at 09:32:53AM -0700, Russ Weight wrote:
>>>>>>>> On 10/13/21 6:49 PM, Xu Yilun wrote:
>>>>>>>>> On Wed, Oct 13, 2021 at 11:09:08AM -0700, Russ Weight wrote:
>>>>>>>>>> On 10/12/21 6:06 PM, Xu Yilun wrote:
>>>>>>>>>>> On Tue, Oct 12, 2021 at 10:20:15AM -0700, Russ Weight wrote:
>>>>>>>>>>>> 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.
>>>>>>>>>>> OK, we can discuss that use case then. But fundamentally a driver should
>>>>>>>>>>> be clear what it is doing.
>>>>>>>>>> The lower-level driver is, of course, clear what it is doing. And the
>>>>>>>>>> FPGA Image Load Framework simply provides a consistent API and manages
>>>>>>>>>> a potentially long-running data transfer in the context of a kernel
>>>>>>>>>> worker thread.
>>>>>>>>>> It sounds like you are saying that that is not "clear enough" in the
>>>>>>>>>> context of the FPGA Manager?
>>>>>>>>>> The files that are used with Intel PAC devices are self-describing. The
>>>>>>>>>> user-space tools, the class driver and the lower-level driver just pass
>>>>>>>>>> the data through to the card BMC without any knowledge of the content,
>>>>>>>>>> purpose or final destination of the data.
>>>>>>>>>> The card BMC will receive signed data, validate it, and process it as a
>>>>>>>>>> BMC image, an FPGA image, a Root Entry Hash, or a key cancellation. In
>>>>>>>>> I category all these actions as firmware update fully or partially on
>>>>>>>>> persistent storage. The FPGA Manager don't have to know the meaning of
>>>>>>>>> every byte on flash, but it should be aware the firmware is updated and
>>>>>>>>> the card may acts differently with a new firmware. This is the common
>>>>>>>>> working model for most of the FPGA cards so that we implement it in FPGA
>>>>>>>>> manager class. 
>>>>>>>>>> the n6000, it could also be part of a multi-step process for programming
>>>>>>>>>> SDM keys and the data may not be stored permanently.
>>>>>>>>> This is new to me, but seems to be different from firmware update, so lets
>>>>>>>>> think about it again.
>>>>>>>>>>> You may try to extend the FPGA framework to
>>>>>>>>>>> support nvmem storage, or image validation, but cannot say we feed the
>>>>>>>>>>> data to any engine undefined by the framework.
>>>>>>>>>> I'm not sure what you mean by "feed the data to any engine undefined by the
>>>>>>>>>> framework". I think the "engine" is the lower level driver/device that invokes
>>>>>>>>>> the fpga_mgr. The lower level driver, of course, is clear what it is doing.
>>>>>>>>>> The fpga_mgr cannot control what driver invokes it.
>>>>>>>>>> Are saying that when invoking the fpga-mgr, that it _must_ also pass descriptive
>>>>>>>>>> data. Meaning that a self-describing file alone is not acceptable?
>>>>>>>>> The class driver should define a reasonable working model and APIs.
>>>>>>>>> Updating the FPGA backup storage is good to me. But receiving a mystery
>>>>>>>>> box and do whatever it requires is not.
>>>>>>>>> Self-describing file is OK, encryption is OK, but either the class
>>>>>>>>> driver itself, or with the help of the low level driver, should make
>>>>>>>>> sure it works within its scope.
>>>>>>>> In our secure update process, the card BMC firmware authenticates
>>>>>>>> the data using the root entry hashes and will either reject the
>>>>>>>> data or perform some function based on the contents. Neither the
>>>>>>>> user-space, the class driver, nor the lower level driver know
>>>>>>>> what the contents are. It _is_ a "mystery box" to them. How do we
>>>>>>>> verify scope in this model?
>>>>>>> I think we need to find out how. One case is, the HW is designed to have
>>>>>>> one single function, such as firmware update, then any image input
>>>>>>> through firmware update API is within expectation, and the driver
>>>>>>> should only serve the firmware update API. I think this is how the
>>>>>>> N3000 is working now. If the HW is for another function, register itself
>>>>>>> to serve another API, or another class driver.
>>>>>>> Another case is, the HW could do multiple types of tasks depending on
>>>>>>> the content of the image, such as firmware update, image verification,
>>>>>>> or assumably power off the card ... There should be some mechanism for
>>>>>>> the driver to only accept the right image according to what API is called.
>>>>>>> Or the user may input an image named update_the_card.img through
>>>>>>> firmware update API and finally get the card off. Having some headers
>>>>>>> readable by host for the operation type? Or, some HW interface for host
>>>>>>> to apply the operation type as well as the image, let the HW verify?
>>>>>>> Let's think about it.
>>>>>> I'm not sure if I am following your thinking here. The HW, of course,
>>>>>> verifies authentication of the image and acts according to the image
>>>>>> type. I don't think it is reasonable to require the class driver to
>>>>>> interpret the data to determine what it is. That implies that the
>>>>>> class driver would have to know the header format and possible values.
>>>>>> It also means that changes to the header format would require patches
>>>>>> to the class driver.
>>>>>> The FPGA card is trusted by virtue of the fact that the customer
>>>>>> purchased it and physically placed it in the machine. If the FPGA card
>>>>>> (or the lower level driver) validates the image, then why does the
>>>>>> Class driver need to be concerned about the file type? I think the
>>>>>> purpose of the class driver is primarily to provide a common API and
>>>>>> perform common functions so that they don't have to be replicated
>>>>>> among similar low-level drivers. It is up to the low-level driver
>>>>>> or the device itself to ensure that the data received is acceptable.
>>>>>> If the card receives data through the fpga-mgr upload facility that
>>>>>> isn't strictly a firmware update, and if the lower-level driver or
>>>>>> the card handles it and returns appropriate status - is that really
>>>>>> a problem?
>>>>>>>> As you have noted, most current cases result in a change to the
>>>>>>>> card, and I suspect that it will remain that way. But that can't be
>>>>>>>> guaranteed, and I'm not convinced that a host driver needs to be
>>>>>>>> concerned about it.
>>>>>>> A host driver should know what is done, in some abstraction level.
>>>>>>> I think updating the persistent storage is an acceptable abstraction
>>>>>>> in FPGA domain, so I'd like to extend it in FPGA manager. But doing
>>>>>>> anything according to the image is not.
>>>>>> By host driver, do you mean the class driver? Or the lower-level device
>>>>>> driver?
>>>>> The class driver.
>>>>>> It seems to me that you are saying that self-describing images are not
>>>>>> acceptable? Or at least they are not acceptable payload for an FPGA
>>>>>> Manager firmware-update API?
>>>>> For N3000, we are working on the persistent storage update APIs, which is
>>>>> a much simpler working model, no runtime device change, and needs no
>>>>> device removal & re-enumeration.
>>>>> But if you need to extend something more that would potentially changes
>>>>> the behavior of the running devices on FPGA, device removal &
>>>>> re-enumeration are needed so that the system knows what devices are
>>>>> changed.
>>>>>> The FPGA Image Load Framework was designed with the concept of
>>>>>> transferring data to a device without imposing a purpose on the data.
>>>>>> The expectation is that the lower-level driver or the device will
>>>>>> validate the data. Is there something fundamentally wrong with that
>>>>> I think there is something wrong here. As I said before, persistent
>>>>> storage updating has different software process from some runtime
>>>>> updating, so the class driver should be aware of what the HW engine
>>>>> is doing.
>>>> So far, there are no self-describing images that cause a
>>>> change in run-time behavior, and I don't think that will
>>>> happen for the very reason that the class-driver would
>>>> need to know about it.
>>> Again, the class driver needs to know what is happening, at some
>>> abstraction level, to ensure the system is aligned with the HW state.
>>> If the class driver cannot tell the detail, it has to assume the
>>> whole FPGA region will be changed, and removal & re-enumeration is
>>> needed.
>> So we make it a requirement that the self-describing files
>> cannot make changes that require the class driver to manage
>> state.
> The API should not only define what it won't do, but also define what
> it will do. But the "image load" just specifies the top half of the
> process. So I don't think this API would be accepted.
So what is the path forward. It seems like you are saying
that the self-describing files do not fit in the fpga-mgr.
Can we reconsider the FPGA Image Load Framework, which does
not make any assumptions about the contents of the image

>>>> When I asserted that not all self-describing images are
>>>> changing firmware, I did not mean to imply that they change
>>>> run-time behavior; they do not. They are part of a multi-
>>>> step update of firmware. However, looking at each part of
>>>> the sequence independently, there is at least one instance
>>>> where a certificate is stored in RAM for temporary use.
>>>> When the driver exits from this call, there is no firmware
>>>> change. There is also no change in run-time behavior.
>>>> I'm thinking we could have different IOCTLs:
>>>> (1) firmware  update (address, size, purpose provided
>>>>     with the image)
>>> Will the firmware update use the self-describing files?
>> The firmware update option would be for files that
>> are not self-describing.
>>>> (2) image upload (self-describing files)
>>> If both 1 & 2 use self-describing files, how the class driver verifies
>>> the type of the file without looking into the file?
>> Only 2 would use self-describing files.
> Which IOCTL the N3000 flash secure update will use?
It would use 2. All of our image update files are self-describing.

- Russ
> Thanks,
> Yilun
>> - Russ
>>> For example, if a user calls a firmware update API but inputs an image
>>> upload file, will the class driver block the call? How?
>>>> (3) image validation
>>>> These would all use most of the same code, but the FPGA
>>>> Manager flags and structure fields would be set differently.
>>> This is good to me.
>>> Thanks,
>>> Yilun
>>>> - Russ
>>>>> Thanks,
>>>>> Yilun
>>>>>> approach? And if not, why couldn't we incorporate a similar image_load
>>>>>> API into the FPGA Manager?
>>>>>> - Russ
>>>>>>> Thanks,
>>>>>>> Yilun
>>>>>>>> - Russ
>>>>>>>>> Thanks,
>>>>>>>>> Yilun
>>>>>>>>>> Thanks,
>>>>>>>>>> - Russ
>>>>>>>>>>> Thanks,
>>>>>>>>>>> Yilun
>>>>>>>>>>>>> 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:
>>>>>>>>>>>>>> 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,
>>>>>>>>>>>>>>>>> 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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