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Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation
From: |
Alexander Graf |
Subject: |
Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation |
Date: |
Sat, 2 Jul 2011 14:28:04 +0200 |
Am 02.07.2011 um 15:50 schrieb Hannes Reinecke <address@hidden>:
> 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.
Ah, might be a good idea to have some check for that. Just assert() out when
the bounce buffer is too small - or at least tell the user about it. Can the
iov functions tell you if you exceed the write/read side?
>
> (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.)
My hope is that by approaching this incrementally, we can move to a 0-copy
approach later on. But for now, let's focus on getting the device emulation
part well working an in.
>
> But enough of this, Yeah, bugfixing is needed here. I see what I can do.
Thanks :)
Alex
>
- [Qemu-devel] [PATCH 0/3] [v5] Megasas HBA Emulation, Hannes Reinecke, 2011/07/01
- [Qemu-devel] [PATCH 1/3] iov: Update parameter usage in iov_(to|from)_buf(), Hannes Reinecke, 2011/07/01
- [Qemu-devel] [PATCH 2/3] scsi: Add 'hba_private' to SCSIRequest, Hannes Reinecke, 2011/07/01
- [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation, Hannes Reinecke, 2011/07/01
- Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation, Alexander Graf, 2011/07/01
- Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation, Hannes Reinecke, 2011/07/02
- Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation,
Alexander Graf <=
- Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation, Paolo Bonzini, 2011/07/03
- Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation, Hannes Reinecke, 2011/07/04
- Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation, Paolo Bonzini, 2011/07/04
- Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation, Hannes Reinecke, 2011/07/04
- Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation, Paolo Bonzini, 2011/07/04
- Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation, Hannes Reinecke, 2011/07/04
- Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation, Paolo Bonzini, 2011/07/04
- Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation, Stefan Hajnoczi, 2011/07/02
- Re: [Qemu-devel] [PATCH 3/3] megasas: LSI Megaraid SAS emulation, Hannes Reinecke, 2011/07/04
- Re: [Qemu-devel] [PATCH 2/3] scsi: Add 'hba_private' to SCSIRequest, Paolo Bonzini, 2011/07/01