Re: [PATCH v4 2/3] hw/acpi/nvdimm: add a helper to augment SRAT generation

[Verma, Vishal L]

On Thu, 2020-06-04 at 12:33 +0200, Igor Mammedov wrote:
> On Thu, 28 May 2020 16:34:36 -0600
> Vishal Verma <vishal.l.verma@intel.com> wrote:
> 
> > NVDIMMs can belong to their own proximity domains, as described by the
> > NFIT. In such cases, the SRAT needs to have Memory Affinity structures
> > in the SRAT for these NVDIMMs, otherwise Linux doesn't populate node
> > data structures properly during NUMA initialization. See the following
> > for an example failure case.
> > 
> > https://lore.kernel.org/linux-nvdimm/20200416225438.15208-1-vishal.l.verma@intel.com/
> > 
> > Introduce a new helper, nvdimm_build_srat(), and call it for both the
> > i386 and arm versions of 'build_srat()' to augment the SRAT with
> > memory affinity information for NVDIMMs.
> > 
> > The relevant command line options to exercise this are below. Nodes 0-1
> > contain CPUs and regular memory, and nodes 2-3 are the NVDIMM address
> > space.
> > 
> >   -numa node,nodeid=0,mem=2048M,
> >   -numa node,nodeid=1,mem=2048M,
> 
> pls note that 'mem' is about to be disabled for new machine types in favor of 
> memdev
> so this CLI won't work.
> It would be nice to update commit message with memdev variant of CLI

I saw the warnings printed - I did try to use memdevs, but it didn't
quite work with my use case. I'm supplying mem=0 for the pmem/nvdimm
devices that I want to give a specific numa node, but not give them any
more regular memory aside from the nvdimm itself (see nodes 4 and 5
below). And for some reason I couldn't do that with memdevs.

Here is the full command line I'm using for example. I'd appreciate any
pointers on converting over to memdevs fully.

   qemu-system-x86_64 
   -machine pc,accel=kvm,nvdimm, 
   -m 8192M,slots=4,maxmem=40960M 
   -smp 8,sockets=2,cores=2,threads=2 
   -enable-kvm 
   -display none 
   -nographic 
   -drive file=root.img,format=raw,media=disk 
   -kernel ./mkosi.extra/boot/vmlinuz-5.7.0-00001-g87ad963bac23 
   -initrd mkosi.extra/boot/initramfs-5.7.0-00001-g87ad963bac23.img 
   -append selinux=0 audit=0 console=tty0 console=ttyS0 root=/dev/sda2 
ignore_loglevel rw 
   -device e1000,netdev=net0 
   -netdev user,id=net0,hostfwd=tcp::10022-:22 
   -snapshot 
   -numa node,nodeid=0,mem=2048M, 
   -numa cpu,node-id=0,socket-id=0 
   -numa node,nodeid=1,mem=2048M, 
   -numa cpu,node-id=1,socket-id=1 
   -numa node,nodeid=2,mem=2048M, 
   -numa node,nodeid=3,mem=2048M, 
   -numa node,nodeid=4,mem=0, 
   -object 
memory-backend-file,id=nvmem0,share,mem-path=nvdimm-0,size=16384M,align=1G 
   -device nvdimm,memdev=nvmem0,id=nv0,label-size=2M,node=4 
   -numa node,nodeid=5,mem=0, 
   -object 
memory-backend-file,id=nvmem1,share,mem-path=nvdimm-1,size=16384M,align=1G 
   -device nvdimm,memdev=nvmem1,id=nv1,label-size=2M,node=5 

> 
> >   -numa node,nodeid=2,mem=0,
> >   -object 
> > memory-backend-file,id=nvmem0,share,mem-path=nvdimm-0,size=16384M,align=128M
> >   -device nvdimm,memdev=nvmem0,id=nv0,label-size=2M,node=2
> >   -numa node,nodeid=3,mem=0,
> >   -object 
> > memory-backend-file,id=nvmem1,share,mem-path=nvdimm-1,size=16384M,align=128M
> >   -device nvdimm,memdev=nvmem1,id=nv1,label-size=2M,node=3
> > 
> > Cc: Jingqi Liu <jingqi.liu@intel.com>
> > Cc: Michael S. Tsirkin <mst@redhat.com>
> > Reviewed-by: Jingqi Liu <jingqi.liu@intel.com>
> > Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> 
> Reviewed-by: Igor Mammedov <imammedo@redhat.com>

Thanks for the review Igor - I'm pretty unfamiliar with qemu development
- what are the next steps? Is there a certain maintainer/tree I could
watch for the inclusion of this?

> 
> > ---
> >  hw/acpi/nvdimm.c         | 23 +++++++++++++++++++++++
> >  hw/arm/virt-acpi-build.c |  4 ++++
> >  hw/i386/acpi-build.c     |  5 +++++
> >  include/hw/mem/nvdimm.h  |  1 +
> >  4 files changed, 33 insertions(+)
> > 
> >