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Re: [Xen-devel] [PATCH 0/5] pvSCSI (SCSI pass through) driver

To: Jun Kamada <kama@xxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 0/5] pvSCSI (SCSI pass through) driver
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Wed, 24 Oct 2007 08:42:38 +0100
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On 24/10/07 07:22, "Jun Kamada" <kama@xxxxxxxxxxxxxx> wrote:

>> Anyway, the right answer is to ensure that your structures compile the same
>> whether compiled with 32-bit or 64-bit gcc. Check the structure sizes,
>> fields sizes and field offsets.
> You showed me two options in previous email; i.) all the shared-memory
> structures defined in vscsiif.h compile identically for 32-bit and
> 64-bit mode, ii.) to detect the frontend's 'bitness' in scsiback and
> optionally do 32-to-64 or 64-to-32 conversion.
> I consider that current VBD implementation takes option ii.), however
> you recommended me to take option i.) for pvSCSI driver.
> Is my understanding right?

Yes. It was an accident we ended up with structures compiling differently on
32- vs 64-bit. By the time we discovered it was an issue, we couldn't break
backward compatibility.

 -- Keir

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