linux-kernel - Re: [PATCH 1/2] x86: stop using PER_CPU_VAR(kernel

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Message-ID: <20150323134510.2a04e387@gandalf.local.home>
Date:	Mon, 23 Mar 2015 13:45:10 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>, Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] x86: stop using PER_CPU_VAR(kernel_stack)

On Mon, 23 Mar 2015 18:38:09 +0100
Denys Vlasenko <dvlasenk@...hat.com> wrote:

> > Can we do a:
> > 
> >  #define cpu_current_top_of_stack (cpu_tss + TSS_sp0)
> 
> We already do something similar:
> 
> static inline unsigned long current_top_of_stack(void)
> {
> #ifdef CONFIG_X86_64
>         return this_cpu_read_stable(cpu_tss.x86_tss.sp0);
> #else
>         /* sp0 on x86_32 is special in and around vm86 mode. */
>         return this_cpu_read_stable(cpu_current_top_of_stack);
> #endif
> }

So can we then have:

#ifdef __ASSEMBLY__
# define cpu_current_top_of_stack (cpu_tss + TSS_sp0)
#else
# define cpu_current_top_of_stack (cpu_tss.x86_tss.sp0)
#endif

And get rid of that if statement in the static inline?

-- Steve
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