Re: [RFC] cxl/region: set numa node for target memdevs when a region is committed

[Fan Ni <nifan.cxl@gmail.com>]

On Tue, Mar 18, 2025 at 02:25:40PM -0700, Dan Williams wrote:
> Dave Jiang wrote:
> > 
> > 
> > On 3/14/25 9:40 AM, nifan.cxl@gmail.com wrote:
> > > From: Fan Ni <fan.ni@samsung.com>
> > > 
> > > There is a sysfs attribute named "numa_node" for cxl memory device.
> > > however, it is never set so -1 is returned whenever it is read.
> > > 
> > > With this change, the numa_node of each target memdev is set based on the
> > > start address of the hpa_range of the endpoint decoder it associated when a
> > > cxl region is created; and it is reset when the region decoders are
> > > reset.
> > > 
> > > Open qeustion: do we need to set the numa_node when the memdev is
> > > probed instead of waiting until a region is created?
> > 
> > Typically, the numa node for a PCI device should be dev_to_node(),
> > where the device resides. So when the device is probed, it should be
> > set with that. See documentation [1]. Region should have its own NUMA
> > node based on phys_to_target_node() of the starting address.  
> 
> Right, the memdev node is the affinity of device-MMIO to a CPU. The
> HDM-memory that the device decodes may land in multiple proximity
> domains and is subject to CDAT, CXL QoS, HMAT Generic Port, etc...
> 
> If your memdev node is "NUMA_NO_NODE" then that likely means the
> affinity information for the PCI device is missing.
> 
> I would double check that first. See set_dev_node() in device_add().

Thanks Dave and Dan for the explanation. 
Then the issue must be from qemu setup.

I added some debug code as below
---------------------------------------------
fan:~/cxl/linux-fixes$ git diff
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 5a1f05198114..c86a9eb58e99 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -3594,6 +3594,10 @@ int device_add(struct device *dev)
        if (kobj)
                dev->kobj.parent = kobj;
 
+        dev_dbg(dev, "device: '%s': %s XX node %d\n", dev_name(dev), __func__, dev_to_node(dev));
+        if (parent) {
+                dev_dbg(parent, "parent device: '%s': %s XX node %d\n", dev_name(parent), __func__, dev_to_node(parent));
+        }
        /* use parent numa_node */
        if (parent && (dev_to_node(dev) == NUMA_NO_NODE))
                set_dev_node(dev, dev_to_node(parent));
---------------------------------------------

The output after loading cxl related drivers looks like below. All
numa_node is -1 in the cxl topology. 

Hi Jonathan,
   do I miss something in the qemu setup ??

qemu-system-x86_64 -s  -kernel bzImage -append "root=/dev/sda rw console=ttyS0,115200 ignore_loglevel nokaslr \
cxl_acpi.dyndbg=+fplm cxl_pci.dyndbg=+fplm cxl_core.dyndbg=+fplm cxl_mem.dyndbg=+fplm cxl_pmem.dyndbg=+fplm \
cxl_port.dyndbg=+fplm cxl_region.dyndbg=+fplm cxl_test.dyndbg=+fplm cxl_mock.dyndbg=+fplm \
cxl_mock_mem.dyndbg=+fplm dax.dyndbg=+fplm dax_cxl.dyndbg=+fplm device_dax.dyndbg=+fplm" \
-smp 8 -accel kvm -serial mon:stdio  -nographic  -qmp tcp:localhost:4445,server,wait=off \
-netdev user,id=network0,hostfwd=tcp::2024-:22 -device e1000,netdev=network0  -monitor telnet:127.0.0.1:12346,server,nowait \
-drive file=/home/fan/cxl/images/qemu-image.img,index=0,media=disk,format=raw -machine q35,cxl=on -cpu qemu64,mce=on \
-m 8G,maxmem=64G,slots=8  -virtfs local,path=/opt/lib/modules,mount_tag=modshare,security_model=mapped  \
-virtfs local,path=/home/fan,mount_tag=homeshare,security_model=mapped -object \
memory-backend-file,id=cxl-mem1,share=on,mem-path=/tmp/host//cxltest.raw,size=512M  \ 
-object memory-backend-file,id=cxl-lsa1,share=on,mem-path=/tmp/host//lsa.raw,size=1M \
-device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1,hdm_for_passthrough=true  \
-device cxl-rp,port=0,bus=cxl.1,id=root_port13,chassis=0,slot=2   \
-device cxl-type3,bus=root_port13,memdev=cxl-mem1,lsa=cxl-lsa1,id=cxl-pmem0,sn=0xabcd    \
-M cxl-fmw.0.targets.0=cxl.1,cxl-fmw.0.size=4G,cxl-fmw.0.interleave-granularity=8k

---------------------------------------------
fan:~/cxl/linux-fixes$ cat .config | grep CONFIG_NUMA
# CONFIG_NUMA_BALANCING is not set
CONFIG_NUMA=y
CONFIG_NUMA_KEEP_MEMINFO=y
CONFIG_NUMA_MEMBLKS=y
# CONFIG_NUMA_EMU is not set
fan:~/cxl/linux-fixes$ 

---------------------------------------------
root@debian:~# echo 'file core.c +p' >> /sys/kernel/debug/dynamic_debug/control
root@debian:~# dmesg | grep XX
root@debian:~# dmesg | grep XX
[   44.939510] wakeup wakeup14: device: 'wakeup14': device_add XX node -1
[   44.940195] acpi ACPI0017:00: parent device: 'ACPI0017:00': device_add XX node -1
[   44.941402] cxl root0: device: 'root0': device_add XX node -1
[   44.942023] cxl_acpi ACPI0017:00: parent device: 'ACPI0017:00': device_add XX node -1
[   44.947546] cxl decoder0.0: device: 'decoder0.0': device_add XX node -1
[   44.948219] cxl root0: parent device: 'root0': device_add XX node -1
[   44.958637] cxl port1: device: 'port1': device_add XX node -1
[   44.959245] cxl root0: parent device: 'root0': device_add XX node -1
[   44.990326] cxl decoder1.0: device: 'decoder1.0': device_add XX node -1
[   44.991014] cxl_port port1: parent device: 'port1': device_add XX node -1
[   44.993947] cxl decoder1.1: device: 'decoder1.1': device_add XX node -1
[   44.994593] cxl_port port1: parent device: 'port1': device_add XX node -1
[   44.997521] cxl decoder1.2: device: 'decoder1.2': device_add XX node -1
[   44.998203] cxl_port port1: parent device: 'port1': device_add XX node -1
[   45.001142] cxl decoder1.3: device: 'decoder1.3': device_add XX node -1
[   45.001821] cxl_port port1: parent device: 'port1': device_add XX node -1
[   45.005465] cxl nvdimm-bridge0: device: 'nvdimm-bridge0': device_add XX node -1
[   45.006206] cxl root0: parent device: 'root0': device_add XX node -1
[   45.072975] cxl mem0: device: 'mem0': device_add XX node -1
[   45.073519] cxl_pci 0000:0d:00.0: parent device: '0000:0d:00.0': device_add XX node -1
[   45.074937] firmware mem0: device: 'mem0': device_add XX node -1
[   45.075525] cxl mem0: parent device: 'mem0': device_add XX node -1
[   45.095409] nd ndbus0: device: 'ndbus0': device_add XX node -1
[   45.096135] cxl_nvdimm_bridge nvdimm-bridge0: parent device: 'nvdimm-bridge0': device_add XX node -1
[   45.097476] nd ndctl0: device: 'ndctl0': device_add XX node -1
[   45.099208] nd_bus ndbus0: parent device: 'ndbus0': device_add XX node -1
[   45.101286] cxl pmem0: device: 'pmem0': device_add XX node -1
[   45.102633] cxl_mem mem0: parent device: 'mem0': device_add XX node -1
[   45.108757] nd nmem0: device: 'nmem0': device_add XX node -1
[   45.109317] nd_bus ndbus0: parent device: 'ndbus0': device_add XX node -1
[   45.119846] cxl endpoint2: device: 'endpoint2': device_add XX node -1
[   45.120474] cxl_port port1: parent device: 'port1': device_add XX node -1
[   45.149351] cxl decoder2.0: device: 'decoder2.0': device_add XX node -1
[   45.150029] cxl_port endpoint2: parent device: 'endpoint2': device_add XX node -1
[   45.153057] cxl decoder2.1: device: 'decoder2.1': device_add XX node -1
[   45.153700] cxl_port endpoint2: parent device: 'endpoint2': device_add XX node -1
[   45.156723] cxl decoder2.2: device: 'decoder2.2': device_add XX node -1
[   45.157384] cxl_port endpoint2: parent device: 'endpoint2': device_add XX node -1
[   45.160407] cxl decoder2.3: device: 'decoder2.3': device_add XX node -1
[   45.161073] cxl_port endpoint2: parent device: 'endpoint2': device_add XX node -1
root@debian:~#