linux-kernel - Re: [PATCH 10/24] x86/mm/kaiser: Map the entry stack variables

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Date:   Mon, 27 Nov 2017 18:32:11 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
cc:     Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...capital.net>,
        "H . Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 10/24] x86/mm/kaiser: Map the entry stack variables

On Mon, 27 Nov 2017, Peter Zijlstra wrote:

> On Mon, Nov 27, 2017 at 11:49:09AM +0100, Ingo Molnar wrote:
> > diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
> > index 157f81816915..631e229ab428 100644
> > --- a/arch/x86/kernel/process_64.c
> > +++ b/arch/x86/kernel/process_64.c
> > @@ -59,7 +59,7 @@
> >  #include <asm/unistd_32_ia32.h>
> >  #endif
> >  
> > -__visible DEFINE_PER_CPU(unsigned long, rsp_scratch);
> > +__visible DEFINE_PER_CPU_USER_MAPPED(unsigned long, rsp_scratch);
> >  
> >  /* Prints also some state that isn't saved in the pt_regs */
> >  void __show_regs(struct pt_regs *regs, int all)
> 
> Do we still need this one? It appears to me we'll never actually execute
> that part of entry_SYSCALL_64 anymore, due to
> entry_SYSCALL_64_trampoline.

Unless we use entry_SYSCALL_64 when kaiser is disabled at boottime

Thanks,

	tglx