** Description changed:

  [Impact]
- GRUB times out when downloading downloading large files w/ tftp. This notably 
breaks subiquity based PXE installations on several arm64 platforms (but 
presumably not limited to arm64).
+ 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. !!!!
  
  
- [Test Case]
- This can be reproduced on a Cavium ThunderX CRB system using subiquity from 
the groovy arm64 ISO. Failure looks like:
+ 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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https://bugs.launchpad.net/bugs/1900773

Title:
  Timeout downloading initrd

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