Re: [PATCH v1 1/1] hw/acpi/pci.c: preserve generic initiator insertion order

[Jonathan Cameron via qemu development <qemu-devel@nongnu.org>]

On Tue, 24 Feb 2026 16:22:56 +0000
Ankit Agrawal <ankita@nvidia.com> wrote:

> >> Now the kernel parse it in the sequence of their occurrence. A jumbled up
> >> sequence thus results in a jumbled up assignment.  
> >
> > But what is the actual failure mode here? So the numa IDs are all in a
> > weird order, what goes wrong from that?  
> 
> This interferes with the ability to replicate the numa distance topology
> on host in the VM through qemu command line.
> 
> E.g. consider a NUMA system with 2 sockets each with a GPU.
> 0,1 are the node ids for the sysmem on socket 0,1 respectively and
> 2,3 are the node ids for the GPU memory on socket 0,1 respectively
> dist(0,2) = X
> dist(0,3) = Y
> 
> If we try to replicate this for the VM by passing qemu arguments with
> 4 numa nodes and assign numa distances similar to host, and for the
> sake of example qemu mixes up by putting GI for 3 over 2. The SLIT
> which sets up the distances do it considering the original order in the
> qemu command line.
> https://github.com/qemu/qemu/blob/stable-10.2/hw/acpi/aml-build.c#L2040
> 
> This would lead to a different numa config in terms of distance within
> the VM that the one intended through the qemu command line.

This is the case where I'd like to see an example of the tables before
and after your patch.  If the SLIT is not correctly created wrt to PXMs
(rather than the order of the commands) then we indeed have a QEMU bug that
needs fixing.  However, I'm confused as SLIT should also not be ordered
by command line if the say the command line was:

       -object acpi-generic-initiator,id=gi0,pci-dev=dev0,node=3 \
       -object acpi-generic-initiator,id=gi1,pci-dev=dev0,node=4 \
       -object acpi-generic-initiator,id=gi2,pci-dev=dev0,node=6 \
       -object acpi-generic-initiator,id=gi3,pci-dev=dev0,node=5 \
       -object acpi-generic-initiator,id=gi4,pci-dev=dev0,node=2 \
       -object acpi-generic-initiator,id=gi5,pci-dev=dev0,node=7 \
       -object acpi-generic-initiator,id=gi6,pci-dev=dev0,node=8 \
       -object acpi-generic-initiator,id=gi7,pci-dev=dev0,node=9 \

and numa stuff was something like
       -numa dist,src=3,dst=0,val=100
       -numa dist,src=4,dst=0,val=200
       -numa dist,src=5,dst=0,val=300
       -numa dist,src=6,dst=0,val=100
       -numa dist,src=7,dst=0,val=200
       -numa dist,src=8,dst=0,val=300
       -numa dist,src=9,dst=0,val=100

Then it should be matching src numbers here to node in the GIs whatever the order.

Thanks,

Jonathan


> 
> Thanks
> Ankit Agrawal