RE: [bug #36532] boot in EFI mode (x86_64) fails on some systems

[Stuart_Hayes]

> 
> On 07.06.2012 21:02, address@hidden wrote:
> 
> > Vladimir,
> >
> > On 27 May you had asked me to test a patch to see if it fixed the
> x86_64 EFI boot issue I was seeing
> (http://lists.gnu.org/archive/html/grub-devel/2012-05/msg00064.html).
> >
> > This patch apparently moved the linux real mode allocation into
> grub_linux_boot().  It appeared that the relevant changes (the changes
> in grub-core/loader/i386/linux.c) in the patch you attached to that
> email were already in HEAD, at least by the time I got it.
> 
> >
> > So I will re-work my patch with the changes you requested on 26 May
> (http://lists.gnu.org/archive/html/grub-devel/2012-05/msg00063.html).
> 
> There should be no need for it now. Please test that latest HEAD works
> for you
> 
> --
> Regards
> Vladimir 'φ-coder/phcoder' Serbinenko

Just re-tested HEAD from 7 june.  It doesn't appear that 
grub-core/loader/i386/linux.c has changed from the previous version I tested, 
and it still fails.

I see that your patch to move the EFI memory map buffer allocation into 
grub_linux_boot() is moving the allocation a lot closer to when the buffer is 
used, but it doesn't appear to be close enough.

I added a couple prints, and, on the particular system I'm working with, the 
efi memory map buffer is 16384 bytes when grub_efi_finish_boot_services() is 
called, but it needs a buffer of 18816 bytes to hold the efi memory map at that 
time.

So allocating one additional page for the EFI memory map on top of what is 
currently allocated (which I believe is already one page more than is needed) 
would do the trick on my particular system (in its current configuration), but 
I'd still be worried that it might still break on other systems, since the EFI 
memory map buffer is still being allocated before it is used.

I could submit a patch to do this (as well as to clean up find_efi_mmap_size a 
bit) if you prefer to keep the EFI memory map in real mode memory.  If so, 
please let me know what version you want the patch for (HEAD?).

Thanks,
Stuart