[Bug 1508893] [NEW] TFTP timeout on ARM64 hw when booting from grub that was PXE loaded

[Raghuram Kota]

Public bug reported:

This issue was discovered  with Ubuntu Wily (15.10) on a currently in
development ARM64 HW.

When loading kernel via tftp in grub on this hardware, the system stops
receiving new packets (times out )  after receiving initial few tens of
tftp data packets , which then causes kernel load failure.

Running tcpdump before loading kernel in grub menu shows timeouts
occurring,  as captured in the below log  :

      http://kernel.ubuntu.com/~ming/grub/apm.tcpdump

Following are the  detailed reproduction steps :

1) setup PXE boot entry in UEFI(no any parameter to grub)
2) build one grub from upstream (and/or Wily)  and put it in PXE&TFTP server
3) setup grub config, suppose the shape is like below:
     menuentry 'Install for arm64' {
          linux /ubuntu-installer/arm64/Image --- console=ttyS0,115200
          initrd /ubuntu-installer/arm64/initrd.gz
    }
4) start PXE booting in UEFI
5) grub prompt is coming
6) select 'Install for arm64' menu item and press 'enter' to start
loading kernel
7) then hangs inside loading kernel

** Affects: grub2 (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1508893

Title:
  TFTP timeout on ARM64 hw when booting from grub that was  PXE loaded

Status in grub2 package in Ubuntu:
  New

Bug description:
  This issue was discovered  with Ubuntu Wily (15.10) on a currently in
  development ARM64 HW.

  When loading kernel via tftp in grub on this hardware, the system
  stops receiving new packets (times out )  after receiving initial few
  tens of tftp data packets , which then causes kernel load failure.

  Running tcpdump before loading kernel in grub menu shows timeouts
  occurring,  as captured in the below log  :

        http://kernel.ubuntu.com/~ming/grub/apm.tcpdump

  Following are the  detailed reproduction steps :

  1) setup PXE boot entry in UEFI(no any parameter to grub)
  2) build one grub from upstream (and/or Wily)  and put it in PXE&TFTP server
  3) setup grub config, suppose the shape is like below:
       menuentry 'Install for arm64' {
            linux /ubuntu-installer/arm64/Image --- console=ttyS0,115200
            initrd /ubuntu-installer/arm64/initrd.gz
      }
  4) start PXE booting in UEFI
  5) grub prompt is coming
  6) select 'Install for arm64' menu item and press 'enter' to start
  loading kernel
  7) then hangs inside loading kernel

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