From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jes Sorensen Date: Wed, 22 Aug 2007 07:39:36 +0000 Subject: Re: [PATCH 2/3] dma: override "dma_flags_set_dmaflush" for sn-ia64 Message-Id: <46CBE838.4000302@sgi.com> List-Id: References: <20070818002746.GU1813@sgi.com> <46C94FD5.6000006@sgi.com> <20070821193522.GD5592@sgi.com> <20070821130515.6e745b17.randy.dunlap@oracle.com> <1187729729.18410.48.camel@localhost.localdomain> <20070822003450.GM5592@sgi.com> <1187745249.18410.67.camel@localhost.localdomain> In-Reply-To: <1187745249.18410.67.camel@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: James Bottomley Cc: akepner@sgi.com, Randy Dunlap , linux-kernel , rdreier@cisco.com, linux-ia64 James Bottomley wrote: > On Tue, 2007-08-21 at 17:34 -0700, akepner@sgi.com 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