Re: [PATCH 2/3] dma: override "dma_flags_set_dmaflush" for sn-ia64

From: Jes Sorensen
Date: Wed Aug 22 2007 - 03:41:27 EST


James Bottomley wrote:
On Tue, 2007-08-21 at 17:34 -0700, akepner@xxxxxxx wrote:
The term "posted DMA" is used to describe this behavior in the Altix Device Driver Writer's Guide, but it may be confusing things here. Maybe a better term will suggest itself if I can clarify....

OK, but posted DMA has a pretty specific meaning in terms of PCI, hence
the confusion.

Maybe it would be more better to refer to this as 'out of order DMA'?

On Altix, DMA from a device isn't guaranteed to arrive in host memory in the order it was sent from the device. This reordering can happen in the NUMA interconnect (it's specifically not a PCI reordering.)

This is mmiowb and read_relaxed() again, isn't it?

I believe it's the same problem, except this time it's when exposing
structures to userland.

Cheers,
Jes
-
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/