[arch-general] EFI-GPT : GRUB won't load

[Saleem EDAH-TALLY]

Hello,

I'm trying to dual boot Arch with Windows 8.1 on an HP Pavilion 15-n216sf with 
Windows 8.1 pre-installed.

I have followed 

https://wiki.archlinux.org/index.php/Unified_Extensible_Firmware_Interface 
https://wiki.archlinux.org/index.php/Grub 

I copied the ARCH install ISO to a USB stick with dd and installed ARCH in the 
usual way. Here is the disk layout from cgdisk :

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048          821247   400.0 MiB   2700  Basic data partition
   2          821248         1353727   260.0 MiB   EF00  EFI system partition
   3         1353728         1615871   128.0 MiB   0C01  Microsoft reserved 
...
   4         1615872       167604223   79.1 GiB    0700  Basic data partition
   5      1425895424      1465147391   18.7 GiB    0700  Basic data partition
   6       167604224       209547263   20.0 GiB    8300  ARCH_ROOT
   7       209547264       251490303   20.0 GiB    8300  AUTRE_ROOT
   8       251490304       259878911   4.0 GiB     8200  SWAP
   9       259878912      1425895423   556.0 GiB   8300  HOME

ARCH is installed in /dev/sda6.
/dev/sda4 is where Windows lives, /dev/sda5 is the recovery partition.

In arch-chroot, I mounted the ESP /dev/sda2 in /boot/efi and ran 

grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=grub 
--recheck --debug

with no errors. Then I ran

grub-mkconfig -o /boot/grub/grub.cfg

On boot, GRUB is not loaded at all, the laptop boots on Windows 8.1. After 
pressing F9 fo the boot options menu, there is one entry starting with grub, 
selecting this entry keeps booting Windows. There is a grubx64.efi file in 
/boot/efi/grub.

I have copied /etc/grub.d/40_custom from the section 
https://wiki.archlinux.org/index.php/Grub#Dual-booting
 with the relevant UUID changed to be that of /dev/sda2 (ESP).

So I can't find a way to dual boot with ARCH and I'm stuck with this.

I have noted one weird thing with efibootmgr -v from arch-chroot, with fails 
with an invalid pointer message and lots of backtrace, and the following 
output :

BootCurrent: 0001
Timeout: 2 seconds
BootOrder: 0002,0000,3000,2001,2002,2003
Boot0000* Windows Boot Manager	HD(2,c8800,82000,dc61d0de-af32-472f-8c54-
fdafe931e191)File(\EFI\Microsoft\Boot\bootmgfw.efi)(invalid optional data 
length)
Boot0001* USB Hard Drive (UEFI) - USB DISK 2.0

I am hereby requesting help to solve this issue.

Thank you.