linux-kernel - Re: kmap_atomic_pfn for PCI BAR access?

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Message-ID: <alpine.DEB.0.82.0806260701260.25035@skynet.skynet.ie>
Date:	Thu, 26 Jun 2008 07:02:15 +0100 (IST)
From:	Dave Airlie <airlied@...ux.ie>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
cc:	Keith Packard <keithp@...thp.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Dave Airlie <airlied@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: kmap_atomic_pfn for PCI BAR access?

> >   
> 
> Anything that does any kind of pagetable manipulation needs to do tlb flushes.
> kunmap_atomic handles the flushing.

It doesn't however need to do an IPI dance which is the worst part of 
doing a tlb flush on SMP machines.

flushing local CPU tlbs is bad, but doing IPIs and waiting for everyone 
else is brutal.

Dave.
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