[Bug 1789319] Re: Unable to load shimx64.efi using iPXE over UEFI

[Julian Andres Klode]

Ugh. Let's try to make this clear. Nothing here does http boot. There
are three scenarios, all do PXE TFTP booting:

(1) iPXE network stack replaces firmware one - caused this bug
(2) iPXE without replacing firmware's network stack (CONFIG=qemu) - this works fine
(3) No iPXE, use OVMF's native implementation of PXE booting on virtio-net

(3) only works on virtio, (1, 2) also work on other cards supported by
qemu.

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Title:
  Unable to load shimx64.efi using iPXE over UEFI

Status in MAAS:
  Triaged
Status in grub2 package in Ubuntu:
  Invalid
Status in ipxe package in Ubuntu:
  Fix Released
Status in shim package in Ubuntu:
  Invalid
Status in ipxe source package in Bionic:
  In Progress

Bug description:
  [Impact]
  libvirt supports creating virtual machines running in UEFI mode and uses iPXE to enable network booting. When MAAS gives shimx64.efi, as it does on all UEFI systems, to iPXE it chainloads grub but fails to the grub prompt. If I modify MAAS to give grubx64.efi instead of shimx64.efi UEFI booting works.

  Ideally iPXE would be modified to properly chainload the shim however
  MAAS could also check the user-agent when returning the boot file as
  follows.

  if option arch = 00:00 {
      # pxe
      filename "lpxelinux.0";
  } elsif option arch = 00:07 and exists user-class and option user-class = "iPXE" {
      # iPXE uefi_amd64
      filename "grubx64.efi";
  } elsif option arch = 00:07 {
      # uefi_amd64
      filename "bootx64.efi";
  } elsif option arch = 00:09 and exists user-class and option user-class = "iPXE" {
      # iPXE uefi_amd64
      filename "grubx64.efi";
  } elsif option arch = 00:09 {
      # uefi_amd64
      filename "bootx64.efi";
  } elsif option arch = 00:0B {
      # uefi_arm64
      filename "grubaa64.efi";
  } elsif option arch = 00:0C {
      # open-firmware_ppc64el
      filename "bootppc64.bin";
  } elsif option arch = 00:0E {
      # powernv
      filename "pxelinux.0";
      option path-prefix "ppc64el/";
  } elsif option arch = 00:1F {
      # s390x
      filename "boots390x.bin";
      option path-prefix "s390x/";
  } else {
      # pxe
      filename "lpxelinux.0";
  }

  [Test case]
  Minimal test case:

  Run the following command and ensure it boots (assuming a EFI system with shim and grub):
  sudo kvm -bios /usr/share/OVMF/OVMF_CODE.fd -device virtio-net,netdev=n1 -netdev user,id=n1,tftp=/boot/efi/EFI/ubuntu,bootfile=shimx64.efi

  Optimally, also do the MAAS thing.

  [Regression potential]
  I switched the ipxe-qemu packages to build in qemu mode, which makes things use OVMF's internal network stack (so things might work differently with some bootloaders or something when netbooting). 

  It might do other stuff, too, I don't really know. That said, the
  configuration is specifically for qemu, and used by other
  distributions, so this aligns us more closely with them, reducing
  chances of breaking stuff.

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