Re: [PATCH v2 0/2] extend kexec_file_load system call

Hello Mark,

Sorry for taking this long to respond. I've been focusing on getting my 
kexec_file_load and kexec buffer hand-over series in shape.

Am Donnerstag, 18 August 2016, 11:21:13 schrieb Mark Rutland:

On Thu, Aug 11, 2016 at 08:03:56PM -0300, Thiago Jung Bauermann wrote:

quoted

Device tree blob must be passed to a second kernel on DTB-capable
archs, like powerpc and arm64, but the current kernel interface
lacks this support.

This patch extends kexec_file_load system call by adding an extra
argument to this syscall so that an arbitrary number of file descriptors
can be handed out from user space to the kernel.

See the background [1].

Please note that the new interface looks quite similar to the current
system call, but that it won't always mean that it provides the "binary
compatibility."

[1] http://lists.infradead.org/pipermail/kexec/2016-June/016276.html

As with the original posting, I have a number of concerns, and I'm
really not keen on this.

Thanks for laying out out the reasons for your objection. That's very 
helpful.

* For typical usecases, I do not believe that this is necessary (at
  least for arm64), and generally do not believe that it should be
  necessary for a user to manipulate the DTB (much like the user need
  not manipulate ACPI tables or other FW data structures).

  Other than (potentially) the case of Linux as a flashed-in bootloader,
  I don't see a compelling case for modifying the DTB that could not be
  accomplished in-kernel. For that case, if truly necessary, I think
  that we can get away with something simpler.

Yes, this is the case I am aiming for. I'll experiment with a couple of 
different approaches and see how well they perform.

-- 
[]'s
Thiago Jung Bauermann
IBM Linux Technology Center