On Fri, 12 Mar 2021 09:18:39 -0300 Daniel Henrique Barboza <danie...@linux.ibm.com> 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, 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? > > 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? > I'd say the latter since this is a breaking change and people will want to identify the upstream commits they have to backport to their kernel in order to support the disappearance of "ibm,chip-id". Cheers, -- Greg > > Thanks, > > > DHB > > > > > > C. > > > >> > >> Since the value was used by some PAPR kernels - even if they shouldn't > >> have - I think we should only remove this for newer machine types. We > >> also need to check what we're not supplying that the guest kernel is > >> showing a different number of sockets than specified on the qemu > >> command line. > >> > >>> > >>> Thanks, > >>> > >>> C. > >>> > >>> > >>> > >>> [...] > >>> [...] > >>> [...] > >>> [...] > >>> [...] > >>> [...] > >>> [...] > >>> [...] > >>> [...] > >>> > >> > >> > >
