drivers/cxl/core/port.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
Depending on device/hierarchy readiness, it can be possible for the
async probe process to attempt to register an endpoint before the
entire port hierarchy is ready. This currently fails with -ENXIO.
Return -EPROBE_DEFER to try again later automatically (which is
what the local comments already say we should do anyway).
Signed-off-by: Gregory Price <gourry@gourry.net>
---
drivers/cxl/core/port.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 1d5007e3795a..d6bebf70d142 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -1553,7 +1553,7 @@ static int add_port_attach_ep(struct cxl_memdev *cxlmd,
*/
dev_dbg(&cxlmd->dev, "%s is a root dport\n",
dev_name(dport_dev));
- return -ENXIO;
+ return -EPROBE_DEFER;
}
parent_port = find_cxl_port(dparent, &parent_dport);
--
2.43.0Gregory Price wrote: > Depending on device/hierarchy readiness, it can be possible for the > async probe process to attempt to register an endpoint before the > entire port hierarchy is ready. This currently fails with -ENXIO. > > Return -EPROBE_DEFER to try again later automatically (which is > what the local comments already say we should do anyway). I want to make sure this is not papering over some other issue. Can you post the final topology when this works (cxl list -BPET)? My working theory is that you have 2 devices that share an intermediate port. Otherwise, I am having a hard time understanding why the cxl_bus_rescan() in cxl_acpi_probe() does not obviate the explicit EPROBE_DEFER. So, devA is dependendent on devB to create a common port, but devA loses that race after cxl_bus_rescan() has already run. Then EBPROBE_DEFER is the right answer to trigger devA to try again.
On Fri, Sep 13, 2024 at 09:32:48PM -0700, Dan Williams wrote:
> Gregory Price wrote:
> > Depending on device/hierarchy readiness, it can be possible for the
> > async probe process to attempt to register an endpoint before the
> > entire port hierarchy is ready. This currently fails with -ENXIO.
> >
> > Return -EPROBE_DEFER to try again later automatically (which is
> > what the local comments already say we should do anyway).
>
> I want to make sure this is not papering over some other issue. Can you
> post the final topology when this works (cxl list -BPET)? My working
> theory is that you have 2 devices that share an intermediate port.
> Otherwise, I am having a hard time understanding why the
> cxl_bus_rescan() in cxl_acpi_probe() does not obviate the explicit
> EPROBE_DEFER.
>
Sorry for the delay
[
{
"bus":"root0",
"provider":"ACPI.CXL",
"nr_dports":4,
"dports":[
{
"dport":"pci0000:e0",
"alias":"ACPI0016:00",
"id":7
},
{
"dport":"pci0000:00",
"alias":"ACPI0016:01",
"id":0
},
{
"dport":"pci0000:c0",
"alias":"ACPI0016:02",
"id":6
},
{
"dport":"pci0000:20",
"alias":"ACPI0016:03",
"id":1
}
],
"ports:root0":[
{
"port":"port1",
"host":"pci0000:e0",
"depth":1,
"decoders_committed":2,
"nr_dports":4,
"dports":[
{
"dport":"0000:e0:07.2",
"alias":"device:16",
"id":114
},
{
"dport":"0000:e0:01.1",
"alias":"device:02",
"id":0
},
{
"dport":"0000:e0:01.3",
"alias":"device:05",
"id":2
},
{
"dport":"0000:e0:07.1",
"alias":"device:0d",
"id":113
}
],
"endpoints:port1":[
{
"endpoint":"endpoint5",
"host":"mem0",
"parent_dport":"0000:e0:01.1",
"depth":2,
"decoders_committed":1
}
]
},
{
"port":"port3",
"host":"pci0000:c0",
"depth":1,
"decoders_committed":2,
"nr_dports":1,
"dports":[
{
"dport":"0000:c0:01.1",
"alias":"device:c3",
"id":0
}
],
"endpoints:port3":[
{
"endpoint":"endpoint6",
"host":"mem1",
"parent_dport":"0000:c0:01.1",
"depth":2,
"decoders_committed":1
}
]
},
{
"port":"port2",
"host":"pci0000:00",
"depth":1,
"decoders_committed":0,
"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":"pci0000:20",
"depth":1,
"decoders_committed":0,
"nr_dports":1,
"dports":[
{
"dport":"0000:20:01.1",
"alias":"device:d0",
"id":0
}
]
}
]
}
]
> So, devA is dependendent on devB to create a common port, but devA loses
> that race after cxl_bus_rescan() has already run. Then EBPROBE_DEFER is
> the right answer to trigger devA to try again.
On Wed, Sep 18, 2024 at 01:59:07PM +0200, Gregory Price wrote:
> On Fri, Sep 13, 2024 at 09:32:48PM -0700, Dan Williams wrote:
> > Gregory Price wrote:
> > > Depending on device/hierarchy readiness, it can be possible for the
> > > async probe process to attempt to register an endpoint before the
> > > entire port hierarchy is ready. This currently fails with -ENXIO.
> > >
> > > Return -EPROBE_DEFER to try again later automatically (which is
> > > what the local comments already say we should do anyway).
> >
> > I want to make sure this is not papering over some other issue. Can you
> > post the final topology when this works (cxl list -BPET)? My working
> > theory is that you have 2 devices that share an intermediate port.
> > Otherwise, I am having a hard time understanding why the
> > cxl_bus_rescan() in cxl_acpi_probe() does not obviate the explicit
> > EPROBE_DEFER.
> >
just reporting back with a fully functional layout - they do not appear to
share an intermediate port, unless you consider the root a shared port.
I see your concern about this papering over another issue, but it's not
clear what to look for or how to look for it at this point.
For what it's worth - another group observed the same issue with different
hardware and produced the same patch.
"ports:root0":[
{
"port":"port1",
"host":"pci0000:e0",
"depth":1,
"decoders_committed":1,
"nr_dports":4,
"dports":[
{
"dport":"0000:e0:07.2",
"alias":"device:16",
"id":114
},
{
"dport":"0000:e0:01.1",
"alias":"device:02",
"id":0
},
{
"dport":"0000:e0:01.3",
"alias":"device:05",
"id":2
},
{
"dport":"0000:e0:07.1",
"alias":"device:0d",
"id":113
}
],
"endpoints:port1":[
{
"endpoint":"endpoint5",
"host":"mem0",
"parent_dport":"0000:e0:01.1",
"depth":2,
"decoders_committed":1
}
]
},
{
"port":"port3",
"host":"pci0000:c0",
"depth":1,
"decoders_committed":2,
"nr_dports":1,
"dports":[
{
"dport":"0000:c0:01.1",
"alias":"device:c3",
"id":0
}
],
"endpoints:port3":[
{
"endpoint":"endpoint6",
"host":"mem1",
"parent_dport":"0000:c0:01.1",
"depth":2,
"decoders_committed":2
}
]
},
]
> > So, devA is dependendent on devB to create a common port, but devA loses
> > that race after cxl_bus_rescan() has already run. Then EBPROBE_DEFER is
> > the right answer to trigger devA to try again.
© 2016 - 2026 Red Hat, Inc.