Re: arch_set_user_pkey_access only works on the current task_struct

[liangjs]

On Mon, 2021-06-07 at 10:52 -0700, Dave Hansen wrote:
> On 6/5/21 6:10 AM, Jiashuo Liang wrote:
> > I am learning the kernel implementation of the x86 PKU feature. I find the
> > arch_set_user_pkey_access function in arch/x86/kernel/fpu/xstate.c does not
> > use its first parameter. So it is perhaps a bug?
> 
> I wouldn't really call it a bug.  But, yes, it is something we should
> clean up.

Should we remove the tsk parameter, or allow it to change the PKRU of tsk?

By the way, we are calling write_pkru, which changes both the CPU's PKRU
and the xsave one. Why is this necessary?

If I want to change PKRU of a task_struct other than current, do I still
need to call __write_pkru?

Thank you!
liangjs