On Wed, Jan 09, 2008 at 01:00:38PM -0800, Roland Dreier wrote: > ..... > The reason this hasn't been an issue until now is that almost all > drivers work correctly if the Altix code just sets the "flush" bit for > memory allocated via the consistent/coherent allocators. However, if > we want the device to write to userspace memory, this doesn't work > (and mapping coherent memory allocated in the kernel into userspace is > a mess on other platforms, because it unnecessarily consumes lowmem > and/or kernel address space). >
And the only way that user level CQs work on Altix now is that we apply our own patches to allocate them in the kernel (with dma_alloc_coherent()) them mmap() them back to user space. A bug in one of these patches recently led to considerable drama with several customers - I'd love to get a fix in mainline so we can drop our patches and avoid the possibility such theatrics in the future ;-) -- Arthur -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
