linux-kernel - Re: [PATCH 0/2] [GIT PULL] tracing: various bug fixes

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Date:	Thu, 23 Apr 2009 14:33:07 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Chris Wright <chrisw@...s-sol.org>
cc:	Jeremy Fitzhardinge <jeremy@...p.org>, Ingo Molnar <mingo@...e.hu>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Glauber de Oliveira Costa <gcosta@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH 0/2] [GIT PULL] tracing: various bug fixes



On Thu, 23 Apr 2009, Chris Wright wrote:

> * Chris Wright (chrisw@...s-sol.org) wrote:
> > * Jeremy Fitzhardinge (jeremy@...p.org) wrote:
> > > OK, the good news is that its not a callee-save calling convention  
> > > problem, which is what I feared.  But it does sound pretty awkward to  
> > > fix.  Does __native_flush_tlb_global() have to use  
> > > raw_local_irq_save/restore?
> > 
> > Vaguely related...makes sense to do native_(read/write)_cr4 since it's
> > the native tlb flushing implementation, no?
> > 
> > looks ok from inspection, not tested yet...
> 
> BTW, Steve, does that fix it for you?  Sure makes the code cleaner:

Hi Chris,

I bet it does, but I'm currently reviewing if we need the raw there. I may 
take your patch instead.

I'm about to leave for school so I'll look at this later tonight.

-- Steve

> 
>  410:   0f 20 e2                mov    %cr4,%rdx
>  413:   48 89 d0                mov    %rdx,%rax
>  416:   24 7f                   and    $0x7f,%al
>  418:   0f 22 e0                mov    %rax,%cr4
>  41b:   0f 22 e2                mov    %rdx,%cr4
> 
> thanks,
> -chris
> 
> > Subject: [PATCH] x86: use native register access for native tlb flushing
> > 
> > currently these are paravirtulaized, doesn't appear any callers rely on
> > this (no pv_ops backends are using native_tlb and overriding cr3/4
> > access).
> > 
> > Signed-off-by: Chris Wright <chrisw@...s-sol.org>
> > ---
> >  arch/x86/include/asm/tlbflush.h |    8 ++++----
> >  1 files changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
> > index 16a5c84..a5ecc9c 100644
> > --- a/arch/x86/include/asm/tlbflush.h
> > +++ b/arch/x86/include/asm/tlbflush.h
> > @@ -17,7 +17,7 @@
> >  
> >  static inline void __native_flush_tlb(void)
> >  {
> > -	write_cr3(read_cr3());
> > +	native_write_cr3(native_read_cr3());
> >  }
> >  
> >  static inline void __native_flush_tlb_global(void)
> > @@ -32,11 +32,11 @@ static inline void __native_flush_tlb_global(void)
> >  	 */
> >  	raw_local_irq_save(flags);
> >  
> > -	cr4 = read_cr4();
> > +	cr4 = native_read_cr4();
> >  	/* clear PGE */
> > -	write_cr4(cr4 & ~X86_CR4_PGE);
> > +	native_write_cr4(cr4 & ~X86_CR4_PGE);
> >  	/* write old PGE again and flush TLBs */
> > -	write_cr4(cr4);
> > +	native_write_cr4(cr4);
> >  
> >  	raw_local_irq_restore(flags);
> >  }
> 
--
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