Based on kernel version 6.16. Page generated on 2025-08-06 08:57 EST.
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.. SPDX-License-Identifier: GPL-2.0
======================
Multi-Level Interleave
======================
This cxl-cli configuration dump shows the following host configuration:
* A single socket system with one CXL root
* CXL Root has Four (4) CXL Host Bridges
* Two CXL Host Bridges have a two CXL Memory Expanders Attached each.
* The CXL root is configured to interleave across the two host bridges.
* Each host bridge with expanders interleaves across two endpoints.
This output is generated by :code:`cxl list -v` and describes the relationships
between objects exposed in :code:`/sys/bus/cxl/devices/`.
::
[
{
"bus":"root0",
"provider":"ACPI.CXL",
"nr_dports":4,
"dports":[
{
"dport":"pci0000:00",
"alias":"ACPI0016:01",
"id":0
},
{
"dport":"pci0000:a8",
"alias":"ACPI0016:02",
"id":4
},
{
"dport":"pci0000:2a",
"alias":"ACPI0016:03",
"id":1
},
{
"dport":"pci0000:d2",
"alias":"ACPI0016:00",
"id":5
}
],
This chunk shows the CXL "bus" (root0) has 4 downstream ports attached to CXL
Host Bridges. The `Root` can be considered the singular upstream port attached
to the platform's memory controller - which routes memory requests to it.
The `ports:root0` section lays out how each of these downstream ports are
configured. If a port is not configured (id's 0 and 1), they are omitted.
::
"ports:root0":[
{
"port":"port1",
"host":"pci0000:d2",
"depth":1,
"nr_dports":3,
"dports":[
{
"dport":"0000:d2:01.1",
"alias":"device:02",
"id":0
},
{
"dport":"0000:d2:01.3",
"alias":"device:05",
"id":2
},
{
"dport":"0000:d2:07.1",
"alias":"device:0d",
"id":113
}
],
This chunk shows the available downstream ports associated with the CXL Host
Bridge :code:`port1`. In this case, :code:`port1` has 3 available downstream
ports: :code:`dport0`, :code:`dport2`, and :code:`dport113`.
::
"endpoints:port1":[
{
"endpoint":"endpoint5",
"host":"mem0",
"parent_dport":"0000:d2:01.1",
"depth":2,
"memdev":{
"memdev":"mem0",
"ram_size":137438953472,
"serial":0,
"numa_node":0,
"host":"0000:d3:00.0"
},
"decoders:endpoint5":[
{
"decoder":"decoder5.0",
"resource":825975898112,
"size":549755813888,
"interleave_ways":4,
"interleave_granularity":256,
"region":"region0",
"dpa_resource":0,
"dpa_size":137438953472,
"mode":"ram"
}
]
},
{
"endpoint":"endpoint6",
"host":"mem1",
"parent_dport":"0000:d2:01.3",
"depth":2,
"memdev":{
"memdev":"mem1",
"ram_size":137438953472,
"serial":0,
"numa_node":0,
"host":"0000:d3:00.0"
},
"decoders:endpoint6":[
{
"decoder":"decoder6.0",
"resource":825975898112,
"size":549755813888,
"interleave_ways":4,
"interleave_granularity":256,
"region":"region0",
"dpa_resource":0,
"dpa_size":137438953472,
"mode":"ram"
}
]
}
],
This chunk shows the endpoints attached to the host bridge :code:`port1`.
:code:`endpoint5` contains a single configured decoder :code:`decoder5.0`
which has the same interleave configuration as :code:`region0` (shown later).
:code:`endpoint6` contains a single configured decoder :code:`decoder5.0`
which has the same interleave configuration as :code:`region0` (shown later).
Next we have the decoders belonging to the host bridge:
::
"decoders:port1":[
{
"decoder":"decoder1.0",
"resource":825975898112,
"size":549755813888,
"interleave_ways":2,
"interleave_granularity":512,
"region":"region0",
"nr_targets":2,
"targets":[
{
"target":"0000:d2:01.1",
"alias":"device:02",
"position":0,
"id":0
},
{
"target":"0000:d2:01.3",
"alias":"device:05",
"position":2,
"id":0
}
]
}
]
},
Host Bridge :code:`port1` has a single decoder (:code:`decoder1.0`), whose
targets are :code:`dport0` and :code:`dport2` - which are attached to
:code:`endpoint5` and :code:`endpoint6` respectively.
The following chunk shows a similar configuration for Host Bridge :code:`port3`,
the second host bridge with a memory device attached.
::
{
"port":"port3",
"host":"pci0000:a8",
"depth":1,
"nr_dports":1,
"dports":[
{
"dport":"0000:a8:01.1",
"alias":"device:c3",
"id":0
},
{
"dport":"0000:a8:01.3",
"alias":"device:c5",
"id":0
}
],
"endpoints:port3":[
{
"endpoint":"endpoint7",
"host":"mem2",
"parent_dport":"0000:a8:01.1",
"depth":2,
"memdev":{
"memdev":"mem2",
"ram_size":137438953472,
"serial":0,
"numa_node":0,
"host":"0000:a9:00.0"
},
"decoders:endpoint7":[
{
"decoder":"decoder7.0",
"resource":825975898112,
"size":549755813888,
"interleave_ways":4,
"interleave_granularity":256,
"region":"region0",
"dpa_resource":0,
"dpa_size":137438953472,
"mode":"ram"
}
]
},
{
"endpoint":"endpoint8",
"host":"mem3",
"parent_dport":"0000:a8:01.3",
"depth":2,
"memdev":{
"memdev":"mem3",
"ram_size":137438953472,
"serial":0,
"numa_node":0,
"host":"0000:a9:00.0"
},
"decoders:endpoint8":[
{
"decoder":"decoder8.0",
"resource":825975898112,
"size":549755813888,
"interleave_ways":4,
"interleave_granularity":256,
"region":"region0",
"dpa_resource":0,
"dpa_size":137438953472,
"mode":"ram"
}
]
}
],
"decoders:port3":[
{
"decoder":"decoder3.0",
"resource":825975898112,
"size":549755813888,
"interleave_ways":2,
"interleave_granularity":512,
"region":"region0",
"nr_targets":1,
"targets":[
{
"target":"0000:a8:01.1",
"alias":"device:c3",
"position":1,
"id":0
},
{
"target":"0000:a8:01.3",
"alias":"device:c5",
"position":3,
"id":0
}
]
}
]
},
The next chunk shows the two CXL host bridges without attached endpoints.
::
{
"port":"port2",
"host":"pci0000:00",
"depth":1,
"nr_dports":2,
"dports":[
{
"dport":"0000:00:01.3",
"alias":"device:55",
"id":2
},
{
"dport":"0000:00:07.1",
"alias":"device:5d",
"id":113
}
]
},
{
"port":"port4",
"host":"pci0000:2a",
"depth":1,
"nr_dports":1,
"dports":[
{
"dport":"0000:2a:01.1",
"alias":"device:d0",
"id":0
}
]
}
],
Next we have the `Root Decoders` belonging to :code:`root0`. This root decoder
applies the interleave across the downstream ports :code:`port1` and
:code:`port3` - with a granularity of 256 bytes.
This information is generated by the CXL driver reading the ACPI CEDT CMFWS.
::
"decoders:root0":[
{
"decoder":"decoder0.0",
"resource":825975898112,
"size":549755813888,
"interleave_ways":2,
"interleave_granularity":256,
"max_available_extent":0,
"volatile_capable":true,
"nr_targets":2,
"targets":[
{
"target":"pci0000:a8",
"alias":"ACPI0016:02",
"position":1,
"id":4
},
{
"target":"pci0000:d2",
"alias":"ACPI0016:00",
"position":0,
"id":5
}
],
Finally we have the `Memory Region` associated with the `Root Decoder`
:code:`decoder0.0`. This region describes the overall interleave configuration
of the interleave set. So we see there are a total of :code:`4` interleave
targets across 4 endpoint decoders.
::
"regions:decoder0.0":[
{
"region":"region0",
"resource":825975898112,
"size":549755813888,
"type":"ram",
"interleave_ways":4,
"interleave_granularity":256,
"decode_state":"commit",
"mappings":[
{
"position":3,
"memdev":"mem3",
"decoder":"decoder8.0"
},
{
"position":2,
"memdev":"mem1",
"decoder":"decoder6.0"
}
{
"position":1,
"memdev":"mem2",
"decoder":"decoder7.0"
},
{
"position":0,
"memdev":"mem0",
"decoder":"decoder5.0"
}
]
}
]
}
]
}
]
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