linux-kernel - Re: [PATCH v17 0/5] FPGA Image Load (previously Security Manager)

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Message-ID: <20211012074944.GC95330@yilunxu-OptiPlex-7050>
Date:   Tue, 12 Oct 2021 15:49:44 +0800
From:   Xu Yilun <yilun.xu@...el.com>
To:     Tom Rix <trix@...hat.com>
Cc:     Russ Weight <russell.h.weight@...el.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 Mon, Oct 11, 2021 at 05:35:03AM -0700, 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.
> > > > 
> > > > 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.
> > > > 
> > > > 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.

Yes, we could have a flag and optionally threading the writing.

Thanks,
Yilun

> 
> Tom
> 
> > 
> > Thanks,
> > Yilun
> > 
> > > Any other driver would do similar.
> > > 
> > > Is this close to what you are thinking ?
> > > 
> > > Tom
> > > 
> > > > Thanks,
> > > > Yilun
> > > >