Message-ID: <47386907.5080101@redhat.com>
Date: Mon, 12 Nov 2007 15:53:59 +0100
From: Gerd Hoffmann <kraxel@redhat.com>
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To: Muli Ben-Yehuda <muli@il.ibm.com>
CC: Amit Shah <amit.shah@qumranet.com>, kvm-devel@lists.sourceforge.net,
       linux-kernel@vger.kernel.org
Subject: Re: [kvm-devel] [PATCH 3/8] KVM: PVDMA Guest: Guest-side routines
 for paravirtualized DMA
References: <d1c72ce6e3a0e73c18993c3f066d1350b147f726.1194445109.git.amit.shah@qumranet.com>	<609d5d611a5fb58ab5a7184be7b6d29494023ba0.1194445109.git.amit.shah@qumranet.com> <20071112105001.GF3299@rhun.haifa.ibm.com>
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Muli Ben-Yehuda wrote:
> On Wed, Nov 07, 2007 at 04:21:04PM +0200, Amit Shah wrote:
> 
>> We make the dma_mapping_ops structure to point to our structure so
>> that every DMA access goes through us. (This is the reason this only
>> works for 64-bit guest. 32-bit guest doesn't yet have a dma_ops
>> struct.)
> 
> I need the same facility for Calgary for falling back to swiotlb if a
> translation is disabled on some slot, and IB needs the same facility
> for some IB adapters (e.g., ipath). Perhaps it's time to consider
> stackable dma-ops (unless someone has a better idea...).

Hmm, at least the later sounds like for per-device dma_ops would be more
useful that stackable ones, as each stack instance just checks "should I
do something for device $foo, if not, call the next one ...".

cheers,
  Gerd

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