Re: [PATCH 1/8] hmat acpi: Don't require initiator value in -numa

[Brice Goglin]

Le 18/07/2022 à 05:17, Liu, Jingqi a écrit :
> On 7/11/2022 6:44 PM, Hesham Almatary via wrote:
> > From: Brice Goglin <Brice.Goglin@inria.fr>
> >
> > The "Memory Proximity Domain Attributes" structure of the ACPI HMAT
> > has a "Processor Proximity Domain Valid" flag that is currently
> > always set because Qemu -numa requires an initiator=X value
> > when hmat=on. Unsetting this flag allows to create more complex
> > memory topologies by having multiple best initiators for a single
> > memory target.
>
> Do you mean the memory-only numa node requires an initiator=X value ?
>
> It would be better if you can explicitly provide cases in the description
>
> for creating more complex memory topologies without initiator=X.


Hello

I wrote this text so I am going to reply. All nodes currently require an 
initiator= attribute. For CPU-node, that's usually OK. However it forces 
all nodes to have a best initiator that is exactly one single node. This 
prevents creating a topology where some memory has for best initiator 
the sum of 2 nodes for instance. There's an example below in the 
description. A real-world example would be a Xeon server with SNC 
enabled: there are 2 DDR per socket, one per SNC, but a single NVDIMM 
per socket covering both SNC. That NVDIMM node cannot have a single 
initiator value since its best initiator is both SNC. That's similar to 
the example below in the description

Brice



> Thanks,
>
> Jingqi
>
> > This patch allows -numa without initiator=X when hmat=on by keeping
> > the default value MAX_NODES in numa_state->nodes[i].initiator.
> > All places reading numa_state->nodes[i].initiator already check
> > whether it's different from MAX_NODES before using it.
> >
> > Tested with
> > qemu-system-x86_64 -accel kvm \
> >   -machine pc,hmat=on \
> >   -drive if=pflash,format=raw,file=./OVMF.fd \
> >   -drive media=disk,format=qcow2,file=efi.qcow2 \
> >   -smp 4 \
> >   -m 3G \
> >   -object memory-backend-ram,size=1G,id=ram0 \
> >   -object memory-backend-ram,size=1G,id=ram1 \
> >   -object memory-backend-ram,size=1G,id=ram2 \
> >   -numa node,nodeid=0,memdev=ram0,cpus=0-1 \
> >   -numa node,nodeid=1,memdev=ram1,cpus=2-3 \
> >   -numa node,nodeid=2,memdev=ram2 \
> >   -numa 
> > hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-latency,latency=10 
> > \
> >   -numa 
> > hmat-lb,initiator=0,target=0,hierarchy=memory,data-type=access-bandwidth,bandwidth=10485760 
> > \
> >   -numa 
> > hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-latency,latency=20 
> > \
> >   -numa 
> > hmat-lb,initiator=0,target=1,hierarchy=memory,data-type=access-bandwidth,bandwidth=5242880 
> > \
> >   -numa 
> > hmat-lb,initiator=0,target=2,hierarchy=memory,data-type=access-latency,latency=30 
> > \
> >   -numa 
> > hmat-lb,initiator=0,target=2,hierarchy=memory,data-type=access-bandwidth,bandwidth=1048576 
> > \
> >   -numa 
> > hmat-lb,initiator=1,target=0,hierarchy=memory,data-type=access-latency,latency=20 
> > \
> >   -numa 
> > hmat-lb,initiator=1,target=0,hierarchy=memory,data-type=access-bandwidth,bandwidth=5242880 
> > \
> >   -numa 
> > hmat-lb,initiator=1,target=1,hierarchy=memory,data-type=access-latency,latency=10 
> > \
> >   -numa 
> > hmat-lb,initiator=1,target=1,hierarchy=memory,data-type=access-bandwidth,bandwidth=10485760 
> > \
> >   -numa 
> > hmat-lb,initiator=1,target=2,hierarchy=memory,data-type=access-latency,latency=30 
> > \
> >   -numa 
> > hmat-lb,initiator=1,target=2,hierarchy=memory,data-type=access-bandwidth,bandwidth=1048576
> > which reports NUMA node2 at same distance from both node0 and node1 
> > as seen in lstopo:
> > Machine (2966MB total) + Package P#0
> >    NUMANode P#2 (979MB)
> >    Group0
> >      NUMANode P#0 (980MB)
> >      Core P#0 + PU P#0
> >      Core P#1 + PU P#1
> >    Group0
> >      NUMANode P#1 (1007MB)
> >      Core P#2 + PU P#2
> >      Core P#3 + PU P#3
> >
> > Before this patch, we had to add ",initiator=X" to "-numa 
> > node,nodeid=2,memdev=ram2".
> > The lstopo output difference between initiator=1 and no initiator is:
> > @@ -1,10 +1,10 @@
> >   Machine (2966MB total) + Package P#0
> > +  NUMANode P#2 (979MB)
> >     Group0
> >       NUMANode P#0 (980MB)
> >       Core P#0 + PU P#0
> >       Core P#1 + PU P#1
> >     Group0
> >       NUMANode P#1 (1007MB)
> > -    NUMANode P#2 (979MB)
> >       Core P#2 + PU P#2
> >       Core P#3 + PU P#3
> >
> > Corresponding changes in the HMAT MPDA structure:
> > @@ -49,10 +49,10 @@
> >   [078h 0120   2]               Structure Type : 0000 [Memory 
> > Proximity Domain Attributes]
> >   [07Ah 0122   2]                     Reserved : 0000
> >   [07Ch 0124   4]                       Length : 00000028
> > -[080h 0128   2]        Flags (decoded below) : 0001
> > -            Processor Proximity Domain Valid : 1
> > +[080h 0128   2]        Flags (decoded below) : 0000
> > +            Processor Proximity Domain Valid : 0
> >   [082h 0130   2]                    Reserved1 : 0000
> > -[084h 0132   4] Attached Initiator Proximity Domain : 00000001
> > +[084h 0132   4] Attached Initiator Proximity Domain : 00000080
> >   [088h 0136   4]      Memory Proximity Domain : 00000002
> >   [08Ch 0140   4]                    Reserved2 : 00000000
> >   [090h 0144   8]                    Reserved3 : 0000000000000000
> >
> > Final HMAT SLLB structures:
> > [0A0h 0160   2]               Structure Type : 0001 [System Locality 
> > Latency and Bandwidth Information]
> > [0A2h 0162   2]                     Reserved : 0000
> > [0A4h 0164   4]                       Length : 00000040
> > [0A8h 0168   1]        Flags (decoded below) : 00
> >                              Memory Hierarchy : 0
> > [0A9h 0169   1]                    Data Type : 00
> > [0AAh 0170   2]                    Reserved1 : 0000
> > [0ACh 0172   4] Initiator Proximity Domains # : 00000002
> > [0B0h 0176   4]   Target Proximity Domains # : 00000003
> > [0B4h 0180   4]                    Reserved2 : 00000000
> > [0B8h 0184   8]              Entry Base Unit : 0000000000002710
> > [0C0h 0192   4] Initiator Proximity Domain List : 00000000
> > [0C4h 0196   4] Initiator Proximity Domain List : 00000001
> > [0C8h 0200   4] Target Proximity Domain List : 00000000
> > [0CCh 0204   4] Target Proximity Domain List : 00000001
> > [0D0h 0208   4] Target Proximity Domain List : 00000002
> > [0D4h 0212   2]                        Entry : 0001
> > [0D6h 0214   2]                        Entry : 0002
> > [0D8h 0216   2]                        Entry : 0003
> > [0DAh 0218   2]                        Entry : 0002
> > [0DCh 0220   2]                        Entry : 0001
> > [0DEh 0222   2]                        Entry : 0003
> >
> > [0E0h 0224   2]               Structure Type : 0001 [System Locality 
> > Latency and Bandwidth Information]
> > [0E2h 0226   2]                     Reserved : 0000
> > [0E4h 0228   4]                       Length : 00000040
> > [0E8h 0232   1]        Flags (decoded below) : 00
> >                              Memory Hierarchy : 0
> > [0E9h 0233   1]                    Data Type : 03
> > [0EAh 0234   2]                    Reserved1 : 0000
> > [0ECh 0236   4] Initiator Proximity Domains # : 00000002
> > [0F0h 0240   4]   Target Proximity Domains # : 00000003
> > [0F4h 0244   4]                    Reserved2 : 00000000
> > [0F8h 0248   8]              Entry Base Unit : 0000000000000001
> > [100h 0256   4] Initiator Proximity Domain List : 00000000
> > [104h 0260   4] Initiator Proximity Domain List : 00000001
> > [108h 0264   4] Target Proximity Domain List : 00000000
> > [10Ch 0268   4] Target Proximity Domain List : 00000001
> > [110h 0272   4] Target Proximity Domain List : 00000002
> > [114h 0276   2]                        Entry : 000A
> > [116h 0278   2]                        Entry : 0005
> > [118h 0280   2]                        Entry : 0001
> > [11Ah 0282   2]                        Entry : 0005
> > [11Ch 0284   2]                        Entry : 000A
> > [11Eh 0286   2]                        Entry : 0001
> >
> > Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>
> > ---
> >   hw/core/machine.c | 4 +---
> >   1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/hw/core/machine.c b/hw/core/machine.c
> > index a673302cce..d4d7e77401 100644
> > --- a/hw/core/machine.c
> > +++ b/hw/core/machine.c
> > @@ -1173,9 +1173,7 @@ static void numa_validate_initiator(NumaState 
> > *numa_state)
> >         for (i = 0; i < numa_state->num_nodes; i++) {
> >           if (numa_info[i].initiator == MAX_NODES) {
> > -            error_report("The initiator of NUMA node %d is missing, 
> > use "
> > -                         "'-numa node,initiator' option to declare 
> > it", i);
> > -            exit(1);
> > +            continue;
> >           }
> >             if (!numa_info[numa_info[i].initiator].present) {

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