linux-kernel - Re: [PATCH] x86: create array based interface to change page attribute

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Date:	31 Mar 2008 09:25:12 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Dave Airlie <airlied@...hat.com>
Cc:	linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
	arjan@...ux.intel.com, thomas@...gstengraphics.com
Subject: Re: [PATCH] x86: create array based interface to change page attribute

Dave Airlie <airlied@...hat.com> writes:
>  
> +#define CPA_FLUSHTLB 1
> +#define CPA_ARRAY 2

I don't think CPA_ARRAY should be a separate case. Rather single
page flushing should be an array with only a single entry. pageattr
is already very complex, no need to make add more special cases.
> +
> +		/*
> +		 * Only flush present addresses:
> +		 */
> +		if (pte && (pte_val(*pte) & _PAGE_PRESENT))
> +			clflush_cache_range((void *) *addr, PAGE_SIZE);

Also it is doubtful clflush really makes sense on a large array. Just
doing wbinvd might be faster then. Or perhaps better supporting Self-Snoop
should be revisited, that would at least eliminate it on most Intel 
CPUs.

-Andi
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