Re: [PATCH 1/4] hmat acpi: Don't require initiator value in -numa

[Brice Goglin <Brice.Goglin@inria.fr>]

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Le 28/06/2022 à 16:19, Igor Mammedov a écrit :
> On Thu, 23 Jun 2022 16:58:28 +0200
> Brice Goglin <Brice.Goglin@inria.fr> wrote:
>
>> 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.
>>
>> 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
>                                                           ^^^^^^^^
> where does this value come from?


This is #define MAX_NODES 128, the default value for initiator field in 
Qemu. But it's meaningless here because "Processor Proximity Domain 
Valid" flag above is 0.

Brice




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