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Subject: Re: [PATCH v17 0/5] FPGA Image Load (previously Security Manager)
To:     Xu Yilun <yilun.xu@intel.com>
CC:     Tom Rix <trix@redhat.com>, <mdf@kernel.org>,
        <linux-fpga@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <lgoncalv@redhat.com>, <hao.wu@intel.com>,
        <matthew.gerlach@intel.com>
References: <79350773-3629-2734-21c0-0314a762e722@redhat.com>
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 <58036b2d-ca8f-2deb-f1b4-0301d633714b@intel.com>
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 <7d1971d0-b50b-077f-2a82-83d822cd2ad7@intel.com>
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 <2b26bea5-60d3-6763-00e8-9a94fa0bf45b@intel.com>
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From:   Russ Weight <russell.h.weight@intel.com>
Message-ID: <301850cf-9f34-530b-bd9c-fbe9bf9feee5@intel.com>
Date:   Mon, 18 Oct 2021 09:24:08 -0700
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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.

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)
(2) image upload (self-describing files)
(3) image validation

These would all use most of the same code, but the FPGA
Manager flags and structure fields would be set differently.

- 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
>>>>>>>>>>>>>>