linux-kernel - Re: [PATCH v2 13/20] x86/asm/64: Pass sp0 directly to load

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Message-ID: <20171102095331.is3wpxjin5islzzq@gmail.com>
Date:   Thu, 2 Nov 2017 10:53:31 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     X86 ML <x86@...nel.org>, Borislav Petkov <bpetkov@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v2 13/20] x86/asm/64: Pass sp0 directly to load_sp0()


* Ingo Molnar <mingo@...nel.org> wrote:

> 
> * Andy Lutomirski <luto@...nel.org> wrote:
> 
> > load_sp0() had an odd signature:
> > 
> > void load_sp0(struct tss_struct *tss, struct thread_struct *thread);
> > 
> > Simplify it to:
> > 
> > void load_sp0(unsigned long sp0);
> 
> I also added this to the changelog:
> 
> > Also simplify a few get_cpu()/put_cpu() sequences to
> > preempt_disable()/preempt_enable().
> 
> Plus:
> 
> > --- a/arch/x86/kernel/cpu/common.c
> > +++ b/arch/x86/kernel/cpu/common.c
> > @@ -1572,7 +1572,7 @@ void cpu_init(void)
> >  	initialize_tlbstate_and_flush();
> >  	enter_lazy_tlb(&init_mm, me);
> >  
> > -	load_sp0(t, &current->thread);
> > +	load_sp0(current->thread.sp0);
> >  	set_tss_desc(cpu, t);
> >  	load_TR_desc();
> >  	load_mm_ldt(&init_mm);
> > @@ -1627,7 +1627,7 @@ void cpu_init(void)
> >  	initialize_tlbstate_and_flush();
> >  	enter_lazy_tlb(&init_mm, curr);
> >  
> > -	load_sp0(t, thread);
> > +	load_sp0(thread->sp0);
> >  	set_tss_desc(cpu, t);
> >  	load_TR_desc();
> >  	load_mm_ldt(&init_mm);
> 
> In the 32-bit path this was the last use of 'thread', making the local variable 
> unused - I removed it.

Correction, it's patch #16 that removes the last reference:

   [PATCH v2 16/20] x86/boot/64: Stop initializing TSS.sp0 at boot

I removed the local variable there.

Thanks,

	Ingo