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Message-ID: <1336727058.2527.144.camel@twins>
Subject: Re: [PATCH v4 5/7] x86/tlb: add tlb flush all factor for specific
 CPU
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Alex Shi <alex.shi@intel.com>
Cc: rob@landley.net, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
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Date: Fri, 11 May 2012 11:04:18 +0200
In-Reply-To: <4FAC621D.2020704@intel.com>
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On Fri, 2012-05-11 at 08:49 +0800, Alex Shi wrote:
> On 05/10/2012 05:38 PM, Peter Zijlstra wrote:
> 
> > On Thu, 2012-05-10 at 13:00 +0800, Alex Shi wrote:
> > 
> > 
> >> +void intel_tlb_flushall_factor_set(struct cpuinfo_x86 *c)
> >> +{
> >> +       if (!cpu_has_invlpg) {
> >> +               tlb_flushall_factor = -1;
> >> +               return;
> >> +       }
> > 
> > ...
> > 
> >> +       if (!cpu_has_invlpg || vma->vm_flags & VM_HUGETLB
> >> +                       || tlb_flushall_factor == (u16)TLB_FLUSH_ALL)
> >> {
> >>  flush_all: 
> > 
> > Since you set tlb_flushall_factor (I'd have called it _shift) to -1
> > when !invlpg there's a redundant check in there.
> > 
> 
> 
> 
> NO, the first judgement is from CPU. But second '-1' is may from user
> setting in sysfs.

Then you're doing it wrong. Don't allow setting the sysfs variable if !
cpu_has_invlpg.