linux-kernel - Re: [PATCH 1/2]Add Variable Page Size and IA64 Support in Intel IOMMU: Generic Part

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Message-ID: <20081003085450.GA27551@elte.hu>
Date:	Fri, 3 Oct 2008 10:54:50 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"Yu, Fenghua" <fenghua.yu@...el.com>
Cc:	Bjorn Helgaas <bjorn.helgaas@...com>,
	"Luck, Tony" <tony.luck@...el.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Avi Kivity <avi@...hat.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>
Subject: Re: [PATCH 1/2]Add Variable Page Size and IA64 Support in Intel
	IOMMU: Generic Part


* Yu, Fenghua <fenghua.yu@...el.com> wrote:

> >What's this all about?  Why do we need #ifdef CONFIG_IA64 here? 
> >Doesn't x86 provide its own readq/writeq implementation?
> 
> This is a comment from Bjorn.
> 
> In my patch, one readq/one writeq are working faster than two 
> readl/two writel on IA64. X86 uses two readl/two writel so that the 
> code works on both x86 and x86-64 although Intel IOMMU only has x86-64 
> version currently. dmar_readq() and dmar_writeq() are in moderate 
> performance critical path.
> 
> Do you think my current implementation is ok to have #ifdef 
> CONFIG_IA64 here? Or I can change X86 to use readq/writeq as well or 
> IA64 uses two readl/two writel for clean code?

yes, clean code is very much preferred for a small detail like this.

	Ingo
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