On Mon, Jul 06, 2015 at 12:10:56PM +1000, Alexey Kardashevskiy wrote: > > (cut-n-paste from kernel patchset) > > Each Partitionable Endpoint (IOMMU group) has an address range on a PCI bus > where devices are allowed to do DMA. These ranges are called DMA windows. > By default, there is a single DMA window, 1 or 2GB big, mapped at zero > on a PCI bus. > > PAPR defines a DDW RTAS API which allows pseries guests > querying the hypervisor about DDW support and capabilities (page size mask > for now). A pseries guest may request an additional (to the default) > DMA windows using this RTAS API. > The existing pseries Linux guests request an additional window as big as > the guest RAM and map the entire guest window which effectively creates > direct mapping of the guest memory to a PCI bus. > > This patchset reworks PPC64 IOMMU code and adds necessary structures > to support big windows. > > Once a Linux guest discovers the presence of DDW, it does: > 1. query hypervisor about number of available windows and page size masks; > 2. create a window with the biggest possible page size (today 4K/64K/16M); > 3. map the entire guest RAM via H_PUT_TCE* hypercalls; > 4. switche dma_ops to direct_dma_ops on the selected PE. > > Once this is done, H_PUT_TCE is not called anymore for 64bit devices and > the guest does not waste time on DMA map/unmap operations. > > Note that 32bit devices won't use DDW and will keep using the default > DMA window so KVM optimizations will be required (to be posted later). > > This patchset adds DDW support for pseries. The host kernel changes are > required, available in the current upstream. > > This patchset is based on git://github.com/dgibson/qemu.git spapr-next branch. > > Please comment. Thanks!
I've applied this to my "spapr-dev" branch. Here's what needs to
happen before I move it into spapr-next (which is what I'll be pushing
to Alex Graf).
* For you and Gavin to test it to see that DDW and EEH work properly
together
* Some word from Alex W on how he wants to go about merging 12-13/14
* Some indication about who should be merging 2/14
* Review from at least one more person - I've looked at so many
versions of the ddw patches I no longer trust that I've got it all
straight in my head
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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