On Wed, Nov 13, 2019 at 5:57 AM Tao Xu <tao3.xu@xxxxxxxxx> wrote: > > On 11/13/2019 5:47 PM, Jonathan Cameron wrote: > > On Tue, 12 Nov 2019 09:55:17 -0800 > > Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > > > >> [ add Tao Xu ] > >> > >> On Fri, Oct 4, 2019 at 4:45 AM Jonathan Cameron > >> <Jonathan.Cameron@xxxxxxxxxx> wrote: > >>> > >>> Generic Initiators are a new ACPI concept that allows for the > >>> description of proximity domains that contain a device which > >>> performs memory access (such as a network card) but neither > >>> host CPU nor Memory. > >>> > >>> This patch has the parsing code and provides the infrastructure > >>> for an architecture to associate these new domains with their > >>> nearest memory processing node. > >> > >> Thanks for this Jonathan. May I ask how this was tested? Tao has been > >> working on qemu support for HMAT [1]. I have not checked if it already > >> supports generic initiator entries, but it would be helpful to include > >> an example of how the kernel sees these configurations in practice. > >> > >> [1]: http://patchwork.ozlabs.org/cover/1096737/ > > > > Tested against qemu with SRAT and SLIT table overrides from an > > initrd to actually create the node and give it distances > > (those all turn up correctly in the normal places). DSDT override > > used to move an emulated network card into the GI numa node. That > > currently requires the PCI patch referred to in the cover letter. > > On arm64 tested both on qemu and real hardware (overrides on tables > > even for real hardware as I can't persuade our BIOS team to implement > > Generic Initiators until an OS is actually using them.) > > > > Main real requirement is memory allocations then occur from one of > > the nodes at the minimal distance when you are do a devm_ allocation > > from a device assigned. Also need to be able to query the distances > > to allow load balancing etc. All that works as expected. > > > > It only has a fairly tangential connection to HMAT in that HMAT > > can provide information on GI nodes. Given HMAT code is quite happy > > with memoryless nodes anyway it should work. QEMU doesn't currently > > have support to create GI SRAT entries let alone HMAT using them. > > > > Whilst I could look at adding such support to QEMU, it's not > > exactly high priority to emulate something we can test easily > > by overriding the tables before the kernel reads them. > > > > I'll look at how hard it is to build an HMAT tables for my test > > configs based on the ones I used to test your HMAT patches a while > > back. Should be easy if tedious. > > > > Jonathan > > > Indeed, HMAT can support Generic Initiator, but as far as I know, QEMU > only can emulate a node with cpu and memory, or memory-only. Even if we > assign a node with cpu only, qemu will raise error. Considering > compatibility, there are lots of work to do for QEMU if we change NUMA > or SRAT table. Thanks for the background. It would still be a useful feature to be able to define a memory + generic-initiator node in qemu. That will mirror real world accelerators with local memory configurations.
