ACK/cmt / APPLIED[Unstable]: [SRU B/D/E/F V2 1/1] efi: efi_get_memory_map -- increase map headroom

[Seth Forshee]

On Fri, Nov 08, 2019 at 10:25:46AM +0000, Andy Whitcroft wrote:
> We are seeing some EFI based machines failing to boot hard in the EFI
> stub:
> 
>     exit_boot() failed!
>     efi_main() failed!
> 
> This seems to occur when the bootloader (grub2 in this case) has had
> to manipulate some additional files due to a change in the way MAAS
> boots the machines.  We tracked this down to the memory map dance
> efi_get_memory_map().  Basically we attempt to close boot services and
> it informs us it cannot do so because it failed to record the updated
> memory map.  This occurs when there is insufficient space in the passed
> memory map buffer to record changes during the operation.  At the point
> when this occurs we are unable to call the allocation functions to
> reallocate the buffer so we panic.
> 
> To avoid this we allocate some additional entries in the buffer to cover
> any additional entries.  This headroom is currently insufficient for
> these machines under this use case.  Increase EFI_MMAP_NR_SLACK_SLOTS to
> provide space for more memory map modifications.
> 
> BugLink: https://bugs.launchpad.net/bugs/1851810
> Signed-off-by: Andy Whitcroft <apw at canonical.com>

Should be marked as a sauce patch. With that changed:

Acked-by: Seth Forshee <seth.forshee at canonical.com>

Applied to unstable/master, thanks!