From: Andi Kleen <ak@muc.de>
To: Terence Ripperda <tripperda@nvidia.com>
Cc: Jon Mason <jdmason@us.ibm.com>,
linux-kernel@vger.kernel.org, mulix@mulix.org
Subject: Re: [PATCH] x86-64: Make GART_IOMMU kconfig help text more specific (trivial)
Date: Thu, 9 Mar 2006 18:47:28 +0100 [thread overview]
Message-ID: <200603091847.29787.ak@muc.de> (raw)
In-Reply-To: <20060310010230.GV8626@hygelac>
On Friday 10 March 2006 02:02, Terence Ripperda wrote:
> > Also, note that the previous help text stated that IOMMU was needed for
> > >3GB memory instead of >4GB. This is fixed in the newer version.
>
> note that many system bioses have memory remapping, to accomodate pci
> i/o ranges. some address space is reserved by the bios for these i/o
> ranges, and as system memory approaches this reserved space, the
> memory is remapped to >4GB. this usually happens around 3.25GB -
> 3.5GB, but probably varies based on bios and pci devices. once this
> memory is remapped to >4GB, the IOMMU kicks in.
>
> so the original text is probably more accurate.
Yep. I already fixed this when applying the patch.
3GB is a rough round number I generally use for this.
-Andi
prev parent reply other threads:[~2006-03-10 1:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-08 21:48 Jon Mason
2006-03-10 1:02 ` Terence Ripperda
2006-03-09 17:47 ` Andi Kleen [this message]
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