linux-kernel - Re: [PATCH v4 7/7] x86/tlb: add tlb_flushall_factor into sysfs for user testing/tuning

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Date:	Fri, 11 May 2012 11:51:36 +0200
From:	Borislav Petkov <bp@...64.org>
To:	Alex Shi <alex.shi@...el.com>
Cc:	rob@...dley.net, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, arnd@...db.de, rostedt@...dmis.org,
	fweisbec@...il.com, jeremy@...p.org, gregkh@...uxfoundation.org,
	riel@...hat.com, luto@....edu, avi@...hat.com, len.brown@...el.com,
	dhowells@...hat.com, fenghua.yu@...el.com, ak@...ux.intel.com,
	cpw@....com, steiner@....com, akpm@...ux-foundation.org,
	penberg@...nel.org, hughd@...gle.com, rientjes@...gle.com,
	kosaki.motohiro@...fujitsu.com, n-horiguchi@...jp.nec.com,
	paul.gortmaker@...driver.com, trenn@...e.de, tj@...nel.org,
	oleg@...hat.com, axboe@...nel.dk, a.p.zijlstra@...llo.nl,
	kamezawa.hiroyu@...fujitsu.com, viro@...iv.linux.org.uk,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 7/7] x86/tlb: add tlb_flushall_factor into sysfs for
 user testing/tuning

On Fri, May 11, 2012 at 08:52:09AM +0800, Alex Shi wrote:
> >> +#ifdef CONFIG_DEBUG_TLBFLUSH
> 
> >> +static ssize_t __tlb_flushall_factor_store(const char *buf,
> >> +					size_t count, int smt)
> >> +{
> >> +	short factor = 0;
> >> +
> >> +	if (sscanf(buf, "%hd", &factor) != 1)
> >> +		return -EINVAL;
> > 
> > This means only single-digit factors, right?
> 
> No, you can try '32' '16' etc. not a 'single-digit'.

Ah, misread sscanf, nevermind.

> > Why not use kstrtoul?
> 
> any advantage of this?

Well, sscanf uses simple_strto* and those miss overflow checks etc, see
33ee3b2e2eb9b4b6c64dcf9ed66e2ac3124e748c for details.

Btw, there are other kstrto* functions which you could use to fit better
the argument type and size passed to tlb_flushall_factor.


-- 
Regards/Gruss,
Boris.

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