Re: [PATCH v6 2/5] x86/kexec: do unconditional WBINVD for bare-metal in relocate_kernel()

[Huang, Kai]

> > --- a/arch/x86/kernel/machine_kexec_64.c
> > +++ b/arch/x86/kernel/machine_kexec_64.c
> > @@ -322,16 +322,9 @@ void machine_kexec_cleanup(struct kimage *image)
> > void machine_kexec(struct kimage *image)  {
> >          unsigned long page_list[PAGES_NR];
> > -       unsigned int host_mem_enc_active;
> >          int save_ftrace_enabled;
> >          void *control_page;
> >
> > -       /*
> > -        * This must be done before load_segments() since if call depth tracking
> > -        * is used then GS must be valid to make any function calls.
> > -        */
> > -       host_mem_enc_active =
> > cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT);
> > -
>
> Functionally the patch looks fine.  I would suggest keeping some form of this comment though, because the limitation about not being able to make function calls after load_segments() is arguably non-obvious and this comment served as a warning for future modifications in this area.

Yeah this makes sense.  Thanks.

I think we can add some text to the existing comment of load_segments() 
to call out this.  Allow me to dig into more about call depth tracking 
to understand it better -- relocate_kernel() after load_segments() seems 
to be a real function call and I want to know how does it interact with 
call depth tracking.