[Bug 1900773] Re: Timeout downloading initrd

[dann frazier]

** Changed in: grub2 (Ubuntu Groovy)
     Assignee: (unassigned) => dann frazier (dannf)

** Changed in: grub2 (Ubuntu Focal)
     Assignee: (unassigned) => dann frazier (dannf)

** Changed in: grub2 (Ubuntu Bionic)
     Assignee: (unassigned) => dann frazier (dannf)

** Changed in: grub2 (Ubuntu Xenial)
     Assignee: (unassigned) => dann frazier (dannf)

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

Title:
  Timeout downloading initrd

Status in Release Notes for Ubuntu:
  New
Status in grub2 package in Ubuntu:
  Fix Released
Status in livecd-rootfs package in Ubuntu:
  Invalid
Status in grub2 source package in Xenial:
  Fix Committed
Status in grub2 source package in Bionic:
  Fix Committed
Status in grub2 source package in Focal:
  Fix Committed
Status in livecd-rootfs source package in Focal:
  Invalid
Status in grub2 source package in Groovy:
  Fix Committed
Status in livecd-rootfs source package in Groovy:
  Invalid
Status in grub2 source package in Hirsute:
  Fix Released
Status in livecd-rootfs source package in Hirsute:
  Invalid

Bug description:
  [Impact]
  GRUB times out when downloading downloading large files w/ tftp. This notably breaks subiquity based PXE installs which feature a large initrd. (Observed on several arm64 platforms, though the symptom is not arch-specific).

  [Test Case]
  Simple test case using an x86 UEFI VM:
  Place a kernel/ramdisk on a tftp server. Inflate the initrd or kernel to 87M, e.g.:

  dd if=/dev/zero of=initrd.img bs=1M count=87
  dd if=initrd.img.orig of=initrd.img conv=notrunc

  Success looks like:
  Shell> fs0:
  FS0:\> \efi\grubnetx64.efi
  grub> net_dhcp efinet0
  grub> linux (tftp,192.168.122.1)/vmlinuz.orig console=ttyS0,115200n8
  grub> initrd (tftp,192.168.122.1)/initrd.img
  grub> 

  Failure looks like:

  grub> net_dhcp efinet0
  grub> linux (tftp,192.168.122.1)/vmlinuz.orig console=ttyS0,115200n8
  grub> initrd (tftp,192.168.122.1)/initrd.img
  !!!! X64 Exception Type - 06(#UD - Invalid Opcode)  CPU Apic ID - 00000000 !!!!
  RIP  - 0000000000099080, CS  - 0000000000000038, RFLAGS - 0000000000010286
  RAX  - 000000007DC2FF00, RCX - 000000004FF99013, RDX - 000000007BF4CCF4
  RBX  - 000000007BE43FC0, RSP - 000000007FF25AE8, RBP - 000000007BE3C2A0
  RSI  - 000000000000000B, RDI - 000000007BE3C340
  R8   - 000000007DC21168, R9  - 000000007DC1D4AE, R10 - 0000000000000067
  R11  - 0000000000000002, R12 - 000000007BE3CCA0, R13 - 000000007BE3C260
  R14  - 0000000000020004, R15 - 000000007DC1A613
  DS   - 0000000000000030, ES  - 0000000000000030, FS  - 0000000000000030
  GS   - 0000000000000030, SS  - 0000000000000030
  CR0  - 0000000080010033, CR2 - 0000000000000000, CR3 - 000000007FC01000
  CR4  - 0000000000000668, CR8 - 0000000000000000
  DR0  - 0000000000000000, DR1 - 0000000000000000, DR2 - 0000000000000000
  DR3  - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 - 0000000000000400
  GDTR - 000000007F9EE698 0000000000000047, LDTR - 0000000000000000
  IDTR - 000000007F4B2018 0000000000000FFF,   TR - 0000000000000000
  FXSAVE_STATE - 000000007FF25740
  !!!! Can't find image information. !!!!

  
  This was originally discovered on a Cavium ThunderX CRB system using subiquity from the groovy arm64 ISO. Failure there looks like:

                           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...

  [Fix]
  https://git.savannah.gnu.org/cgit/grub.git/commit/?id=a6838bbc6726ad624bd2b94991f690b8e9d23c69

  [Where problems could occur]
  The fix is to the tftp command, so problems would like appear in the tftp stack, possibly due to inconsistencies between tftp server implementations.

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