Re: [Qemu-devel] SPARC iommu mapping

[Blue Swirl]

Thank you for the excellent analysis of the problem! Looks like Qemu doesn't 
handle the case where DMA length and SCSI length are not equal.

> Until here, the addresses are subsequent. Then the next address is much 
> lower:

So Linux splits the transfer into two parts to use two separate pieces of 
buffers. Funny, I thought this situation was exactly the one which virtually 
addressed DMA would prevent from happening.

> What is expected, when the number of bytes from the transfer register have
> been read? Should the hardware raise an interrupt? And if yes, which flags
> must be set?

Yes, there will be an interrupt. I didn't find this situation in the 
NCR53C9X.txt file documenting the ESP, though.

There are two cases:
1 - DMA length shorter than SCSI (your case)
2 - SCSI length shorter (could happen in command replies etc.)

Maybe this patch helps?

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