Re: [PATCH] grub-shell: Add flexibility in QEMU firmware handling

[Gerd Hoffmann]

  Hi,

> > > Do not load the system 32-bit ARM firmware VARS file because it
> > > must be writable to prevent a data exception and boot failure. So
> > > in order to use the VARS file, it must be copied to a writable
> > > location, but its quite large at 64M and is not needed to boot
> > > successfully.
> > 
> > You can load the VARS file with snapshot=on (and drop readonly=on) to
> > make things work without copying the file.
> 
> Good to know. Do you know of any benefit to doing this (ie. using the
> installed VARS file)?

Well, the firmware expects it can write to VARS flash.  ovmf has for
historical reasons code to cope with non-flash or readonly VARS (so
-bios works), but armvirt has not.  Which is why you see the failures.

snapshot=on allows the guest write to a in-RAM throwaway snapshot,
which is the same as using a writable temporary copy of the vars
file, but without the need for a temporary file.

take care,
  Gerd