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Date:   Tue, 19 Oct 2021 08:09:46 -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 10/18/21 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.
>
>> 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.

- 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:
>>>>>>>>>>>>
>>>>>>>>>>>> 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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