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Date: Mon, 04 Jul 2011 08:34:37 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation
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To: Hannes Reinecke <hare@suse.de>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>, Alexander Graf <agraf@suse.de>, Stefan Haynoczi <stefanha@linux.vnet.ibm.com>, qemu-devel@nongnu.org

On 07/04/2011 08:13 AM, Hannes Reinecke wrote:
> On 07/03/2011 04:36 PM, Paolo Bonzini wrote:
>> On 07/02/2011 03:50 PM, Hannes Reinecke wrote:
>>> (And no, I will not getting into another dog-fight with Paul B. here.
>>> Virtio can do without bounce buffers. AHCI can. So I fail to see why
>>> SCSI has to rely on bounce buffers.)
>>
>> I agree, but I do see why a SCSI device might prefer to rely on
>> bounce buffers for non-I/O commands. This is why in my last RFC
>> series for vmw_pvscsi I let the device choose whether to force a
>> bounce buffer or get an external iovec from the HBA.
>>
> Yes, sure, for non-I/O commands it's perfectly okay.
> Most of which will be emulated anyway.
> It's bounce buffers for I/O which kills performance.
>
> But I seem to have missed your last RFC (I'm not reading qemu-devel on a
> regular basis ...).
> Care to send me a pointer to it?

Sure, http://lists.gnu.org/archive/html/qemu-devel/2011-06/msg00668.html

Paolo