Re: [Intel IOMMU][patch 4/8] Supporting Zero Length Reads in Intel IOMMU.

[Andi Kleen]

On Tuesday 24 April 2007 08:03:03 Ashok Raj wrote:
> PCI specs permit zero length reads (ZLR) even if the mapping for that region 
> is write only. Support for this feature is indicated by the presence of a bit 
> in the DMAR capability. If a particular DMAR does not support this capability
> we map write-only regions as read-write.
> 
> This option can also provides a workaround for some drivers that request
> a write-only mapping when they really should request a read-write.
> (We ran into one such case in eepro100.c in handling rx_ring_dma)

Better just fix the drivers instead of adding such hacks

-Andi
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/