Re: [PATCH v6 0/5] x86: Enable LKGS instruction
From: Ingo Molnar
Date: Thu Jan 12 2023 - 07:14:08 EST
* Xin Li <xin3.li@xxxxxxxxx> wrote:
> LKGS instruction is introduced with Intel FRED (flexible return and event
> delivery) specification. As LKGS is independent of FRED, we enable it as
> a standalone CPU feature.
>
> LKGS behaves like the MOV to GS instruction except that it loads the base
> address into the IA32_KERNEL_GS_BASE MSR instead of the GS segment’s
> descriptor cache, which is exactly what Linux kernel does to load user
> level GS base. Thus, with LKGS, there is no need to SWAPGS away from the
> kernel GS base.
Ok, this looks good to me.
I've applied the first 4 patches to tip:x86/cpu, as the instruction exists
in a public document and these patches are fine stand-alone as well, such
as the factoring out of load_gs_index() methods from a high-use low level
header into a new header file.
Planning to apply the final, LKGS enabler patch as well, unless there's any
objections from others?
Thanks,
Ingo