Message-ID: <20211020011608.GA145760@yilunxu-OptiPlex-7050>
Date:   Wed, 20 Oct 2021 09:16:08 +0800
From:   Xu Yilun <yilun.xu@...el.com>
To:     Russ Weight <russell.h.weight@...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 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.

> >
> >> 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?

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:
> >>>>>>>>>>>>
> >>>>>>>>>>>> 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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