A Grub2 EFI image that has the setup_var command.
The setup_var command can modify single bytes within the Setup variable. Some of those are critical for booting, so be careful not to brick your system.
I wanted to enable Intel 'Speed Shift' on my Dell XPS 15 9550 / 9560, and I read online that you could do this by booting some binary blob, and running a 'setup_var' command. As I do not trust some random binary from the internet, I wanted to compile it myself. I figured out that it was simply a Grub2 standalone EFI image with the 'setup_var' command added.
The source code for setup_var I found here: https://github.com/datasone/grub-mod-setup_var but it didn't compile on my system (Ubuntu 18.04), so I forked a recent grub2, and added the command here instead.
Good question. I think it is the marketing term for HWP: Hardware P-States. Here's a description from the Linux documentation:
This driver decides what P-State to use based on the requested policy from the cpufreq core. If the processor is capable of selecting its next P-State internally, then the driver will offload this responsibility to the processor (aka HWP: Hardware P-States). If not, the driver implements algorithms to select the next P-State. https://www.kernel.org/doc/Documentation/cpu-freq/intel-pstate.txt
setup_var 0xD8 0x1
setup_var 0x4BC 0x1
./autogen.sh
./configure --with-platform=efi --prefix=/tmp/grub-with-setup_var
make
make install
cd /tmp/grub-with-setup_var
bin/grub-mkstandalone -O x86_64-efi -o modGRUBShell.efi
Copy the modGRUBShell.efi file to a FAT32 formated USB drive as EFI/BOOT/BOOTX64.EFI.
Reboot, and boot from your USB drive. If it dosen't work, check that UEFI booting is enabled in your BIOS, and that Secure Boot is disabled.
The procedure described here is for configuring the BIOS to provide the ACPI/CPPC table for HWP, which only Windows requires to enable SST/HWP.
Linux' intel_pstate driver does not require ACPI/CPPC to enable HWP. https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6e978b22efa1db9f6e71b24440b5f1d93e968ee3
On linux, you can verify that HWP is enabled as follows:
$ dmesg | grep -i hwp
[ 1.678647] intel_pstate: HWP enabled
After patching my XPS 15 9550, I can also see the updated ACPI/CPPC table:
$ dmesg | grep -i hwp
[ 0.276999] ACPI: SSDT 0xFFFF92DF6B369000 00008E (v02 PmRef Cpu0Hwp 00003000 INTL 20120913)
[ 0.277413] ACPI: SSDT 0xFFFF92DF6B38E400 000130 (v02 PmRef HwpLvt 00003000 INTL 20120913)
[ 0.279475] ACPI: SSDT 0xFFFF92DF6B38CE00 000119 (v02 PmRef ApHwp 00003000 INTL 20120913)
[ 1.678647] intel_pstate: HWP enabled
- Check out the header of
grub-core/commands/efi/setup_var.c - http://forum.notebookreview.com/threads/dell-xps-speed-shift.796891/
- https://www.kernel.org/doc/Documentation/cpu-freq/intel-pstate.txt