On 3/12/21 1:18 PM, Daniel Henrique Barboza wrote: > > > On 3/12/21 6:53 AM, Cédric Le Goater wrote: >> On 3/12/21 2:55 AM, David Gibson wrote: >>> On Tue, 9 Mar 2021 18:26:35 +0100 >>> Cédric Le Goater <c...@kaod.org> wrote: >>> >>>> On 3/9/21 6:08 PM, Daniel Henrique Barboza wrote: >>>>> >>>>> >>>>> On 3/9/21 12:33 PM, Cédric Le Goater wrote: >>>>>> On 3/8/21 6:13 PM, Greg Kurz wrote: >>>>>>> On Wed, 3 Mar 2021 18:48:50 +0100 >>>>>>> Cédric Le Goater <c...@kaod.org> wrote: >>>>>>> >>>>>>>> The 'chip_id' field of the XIVE CPU structure is used to choose a >>>>>>>> target for a source located on the same chip when possible. This field >>>>>>>> is assigned on the PowerNV platform using the "ibm,chip-id" property >>>>>>>> on pSeries under KVM when NUMA nodes are defined but it is undefined >>>>>>> >>>>>>> This sentence seems to have a syntax problem... like it is missing an >>>>>>> 'and' before 'on pSeries'. >>>>>> >>>>>> ah yes, or simply a comma. >>>>>> >>>>>>>> under PowerVM. The XIVE source structure has a similar field >>>>>>>> 'src_chip' which is only assigned on the PowerNV platform. >>>>>>>> >>>>>>>> cpu_to_node() returns a compatible value on all platforms, 0 being the >>>>>>>> default node. It will also give us the opportunity to set the affinity >>>>>>>> of a source on pSeries when we can localize them. >>>>>>>> >>>>>>> >>>>>>> IIUC this relies on the fact that the NUMA node id is == to chip id >>>>>>> on PowerNV, i.e. xc->chip_id which is passed to OPAL remain stable >>>>>>> with this change. >>>>>> >>>>>> Linux sets the NUMA node in numa_setup_cpu(). On pseries, the hcall >>>>>> H_HOME_NODE_ASSOCIATIVITY returns the node id if I am correct (Daniel >>>>>> in Cc:) >>>> [...] >>>>>> >>>>>> On PowerNV, Linux uses "ibm,associativity" property of the CPU to find >>>>>> the node id. This value is built from the chip id in OPAL, so the >>>>>> value returned by cpu_to_node(cpu) and the value of the "ibm,chip-id" >>>>>> property are unlikely to be different. >>>>>> >>>>>> cpu_to_node(cpu) is used in many places to allocate the structures >>>>>> locally to the owning node. XIVE is not an exception (see below in the >>>>>> same patch), it is better to be consistent and get the same information >>>>>> (node id) using the same routine. >>>>>> >>>>>> >>>>>> In Linux, "ibm,chip-id" is only used in low level PowerNV drivers : >>>>>> LPC, XSCOM, RNG, VAS, NX. XIVE should be in that list also but skiboot >>>>>> unifies the controllers of the system to only expose one the OS. This >>>>>> is problematic and should be changed but it's another topic. >>>>>> >>>>>> >>>>>>> On the other hand, you have the pSeries case under PowerVM that >>>>>>> doesn't xc->chip_id, which isn't passed to any hcall AFAICT. >>>>>> >>>>>> yes "ibm,chip-id" is an OPAL concept unfortunately and it has no meaning >>>>>> under PAPR. xc->chip_id on pseries (PowerVM) will contains an invalid >>>>>> chip id. >>>>>> >>>>>> QEMU/KVM exposes "ibm,chip-id" but it's not used. (its value is not >>>>>> always correct btw) >>>>> >>>>> >>>>> If you have a way to reliably reproduce this, let me know and I'll fix it >>>>> up in QEMU. >>>> >>>> with : >>>> >>>> -smp 4,cores=1,maxcpus=8 -object >>>> memory-backend-ram,id=ram-node0,size=2G -numa >>>> node,nodeid=0,cpus=0-1,cpus=4-5,memdev=ram-node0 -object >>>> memory-backend-ram,id=ram-node1,size=2G -numa >>>> node,nodeid=1,cpus=2-3,cpus=6-7,memdev=ram-node1 >>>> >>>> # dmesg | grep numa >>>> [ 0.013106] numa: Node 0 CPUs: 0-1 >>>> [ 0.013136] numa: Node 1 CPUs: 2-3 >>>> >>>> # dtc -I fs /proc/device-tree/cpus/ -f | grep ibm,chip-id >>>> ibm,chip-id = <0x01>; >>>> ibm,chip-id = <0x02>; >>>> ibm,chip-id = <0x00>; >>>> ibm,chip-id = <0x03>; >>>> >>>> with : >>>> >>>> -smp 4,cores=4,maxcpus=8,threads=1 -object >>>> memory-backend-ram,id=ram-node0,size=2G -numa >>>> node,nodeid=0,cpus=0-1,cpus=4-5,memdev=ram-node0 -object >>>> memory-backend-ram,id=ram-node1,size=2G -numa >>>> node,nodeid=1,cpus=2-3,cpus=6-7,memdev=ram-node1 >>>> >>>> # dmesg | grep numa >>>> [ 0.013106] numa: Node 0 CPUs: 0-1 >>>> [ 0.013136] numa: Node 1 CPUs: 2-3 >>>> >>>> # dtc -I fs /proc/device-tree/cpus/ -f | grep ibm,chip-id >>>> ibm,chip-id = <0x00>; >>>> ibm,chip-id = <0x00>; >>>> ibm,chip-id = <0x00>; >>>> ibm,chip-id = <0x00>; >>>> >>>> I think we should simply remove "ibm,chip-id" since it's not used and >>>> not in the PAPR spec. >>> >>> As I mentioned to Daniel on our call this morning, oddly it *does* >>> appear to be used in the RHEL kernel, even though that's 4.18 based. >>> This patch seems to have caused a minor regression; not in the >>> identification of NUMA nodes, but in the number of sockets shown be >>> lscpu, etc. See https://bugzilla.redhat.com/show_bug.cgi?id=1934421 >>> for more information. >> >> Yes. The property "ibm,chip-id" is wrongly calculated in QEMU. If we >> remove it, we get with 4.18.0-295.el8.ppc64le or 5.12.0-rc2 : >> >> [root@localhost ~]# lscpu >> Architecture: ppc64le >> Byte Order: Little Endian >> CPU(s): 128 >> On-line CPU(s) list: 0-127 >> Thread(s) per core: 4 >> Core(s) per socket: 16 >> Socket(s): 2 >> NUMA node(s): 2 >> Model: 2.2 (pvr 004e 1202) >> Model name: POWER9 (architected), altivec supported >> Hypervisor vendor: KVM >> Virtualization type: para >> L1d cache: 32K >> L1i cache: 32K >> NUMA node0 CPU(s): 0-63 >> NUMA node1 CPU(s): 64-127 >> >> [root@localhost ~]# grep . >> /sys/devices/system/cpu/*/topology/physical_package_id >> /sys/devices/system/cpu/cpu0/topology/physical_package_id:-1 >> /sys/devices/system/cpu/cpu100/topology/physical_package_id:-1 >> /sys/devices/system/cpu/cpu101/topology/physical_package_id:-1 >> /sys/devices/system/cpu/cpu102/topology/physical_package_id:-1 >> /sys/devices/system/cpu/cpu103/topology/physical_package_id:-1 >> .... >> >> "ibm,chip-id" is still being used on some occasion on pSeries machines. >> This is wrong :/ The problem is : >> >> #define topology_physical_package_id(cpu) (cpu_to_chip_id(cpu)) >> >> We should be using cpu_to_node(). > > > IIUC the "real fix" then is this change you mentioned above, together with > this xive patch as well,
These are independent. The XIVE patch just raised the issue because it's another usage example of cpu_to_chip_id() or directly "ibm,chip-id" in the XIVE case, on a pseries machine. The use of cpu_to_node(cpu) for topology_physical_package_id(cpu) is a fix for the sysfs issue reported in the redhat BZ. > to stop using ibm,chip-id for good in the pserie > kernel. With these changes QEMU can remove 'ibm,chip-id' from the pseries > machine without impact. Is this correct? Linux is already "broken" on PowerVM today since we don't have the "ibm,chip-id" property. QEMU is just hiding the problem on KVM. But we have to be bug compatible :) if the QEMU fix is under the pseries-6.x machine we should be fine. > If that's the case, then I believe it's ok to go forward with the QEMU side > change (just for 6.0.0 and newer machines). Or should I wait for the kernel > changes to be merged upstream first? Once Linux is fixed, we shouldn't care if QEMU exports 'ibm,chip-id' or not. I don't think the order is very important. These are independent. C.