[Bug 1900773] Re: thunderx CRB systems tftp timeout downloading initrd

[dann frazier]

On Tue, Oct 20, 2020 at 5:30 PM Steve Langasek
<1900773 at bugs.launchpad.net> wrote:
>
> And is there something intrinsic to this hardware that leads to the
> timeout?

I wonder if there might be a firmware bug. Here's what I see on the
wire:

52120 56.958016 10.229.50.135 10.229.50.84 TFTP 78 Read Request, File:
initrd, Transfer type: octet, blksize=1024, tsize=0
52121 56.960144 10.229.50.84 10.229.50.135 TFTP 72 Option
Acknowledgement, blksize=1024, tsize=90771321
<---snip--->
183218 65.602857 10.229.50.84 10.229.50.135 TFTP 1070 Data Packet, Block: 65535
183219 65.603129 10.229.50.135 10.229.50.84 TFTP 60 Acknowledgement,
Block: 65535
<---snip--->
229458 68.561417 10.229.50.135 10.229.50.84 TFTP 60 Acknowledgement,
Block: 88643
229459 68.561466 10.229.50.84 10.229.50.135 TFTP 935 Data Packet,
Block: 88644 (last)
229460 68.561519 10.229.50.135 10.229.50.84 TFTP 60 Acknowledgement,
Block: 88644
229462 68.962413 10.229.50.135 10.229.50.84 TFTP 60 Acknowledgement,
Block: 65535

It looks like the entire initrd was successfully transferred. The
client ACK'd the last block but then, for some reason, it comes back
about half a second later and re-ACKs a block it had already ACK'd.
And that block being number number 65535 is *interesting*.

> Or would this perhaps work if the machine had a faster network
> link to the tftp server?

Perhaps - but these systems are in the same physical location, slowest
link between is 1Gbps.

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https://bugs.launchpad.net/bugs/1900773

Title:
  thunderx CRB systems tftp timeout downloading initrd

Status in livecd-rootfs package in Ubuntu:
  New

Bug description:
  groovy-live-server-arm64.iso 20201020.1

  When attempting to netboot subiquity on a Cavium ThunderX CRB2S, the
  system always times out downloading the initrd - see below. It seems
  the initrd, which is LZ4 compressed to 87M, is just too large. If I
  recompress the initrd using lzma - shrinking it to 44M, I am able to
  boot it. While that successfully works around the issue, I wouldn't
  expect the average user to know to do it.

                           GNU GRUB  version 2.04

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        Use the  and  keys to select which entry is highlighted.          
        Press enter to boot the selected OS, `e' to edit the commands       
        before booting or `c' for a command-line.                           

  error: timeout reading `initrd'.

  Press any key to continue...

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