Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation

[Hannes Reinecke <hare@suse.de>]

On 07/01/2011 06:42 PM, Alexander Graf wrote:
>
> On 01.07.2011, at 17:35, Hannes Reinecke wrote:
>
>> This patch adds an emulation for the LSI Megaraid SAS 8708EM2 HBA.
>
> Have you tried to execute the current version of megasas and actually
 > do something with it? I just booted up openSUSE 11.4 rescue from DVD
 > with a megasas adapter that contained a raw file backed by tmpfs.
 > Creating a partition worked fine, but when running mkfs.ext3 and
 > mounting afterwards, the mount fails saying there is no ext3 on the disk.
>
> Sounds like data corruption to me :). I know that this used to work
 > a while back, so it might be a regression recently?
>
It worked here, in the sense that I've booted up an existing openSUSE 
11.4 installation. But I wouldn't be surprised if the degradation to use 
bounce-buffers has some flaws.

My guess here is that we have problems when the transfersizes larger as 
the internal bounce buffer.

(I probably should be putting in some more references to 'bounce 
buffers' here to alert people that using bounce buffers in SCSI is the 
best way of killing performance)
(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.)

But enough of this, Yeah, bugfixing is needed here. I see what I can do.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
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