On Tue, Feb 12, 2008 at 01:00:06AM -0800, David Miller wrote: > From: Muli Ben-Yehuda <[EMAIL PROTECTED]> > Date: Tue, 12 Feb 2008 10:52:56 +0200 > > > The streaming DMA-API was designed to conserve IOMMU mappings for > > machines where IOMMU mappings are a scarce resource, and is a poor > > fit for a modern IOMMU such as VT-d with a 64-bit IO address space > > (or even an IOMMU with a 32-bit address space such as Calgary) where > > there are plenty of IOMMU mappings available. > > For the 64-bit case what you are suggesting eventually amounts > to mapping all available RAM in the IOMMU.
Something could be done: we could enable drivers to have DMA-pools they manage that get mapped and are re-used. I would rather the DMA-pools be tied to PID's that way any bad behavior would be limited to the address space of the process using the device. I haven't thought about how hard this would be to do but it would be nice. I think this could be tricky. Application sets up ring buffer of device DMA memory, passes this to driver/stack. Need to handle hitting high water marks and application exit clean up sanely... --mgross > > Although an extreme version of your suggestion, it would be the > most efficient as it would require zero IOMMU flush operations. > > But we'd lose things like protection and other benefits. > -- > 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/ -- 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/
