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Message-ID: <fc546ab5-3ffe-4b72-9d3f-f4807ad4858f@molgen.mpg.de>
Date: Tue, 18 Jun 2024 17:19:27 +0200
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
Yunsheng Lin <linyunsheng@...wei.com>, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: Linux warns `Unknown NUMA node; performance will be reduced`
[Cc: +X86 maintainers]
Dear Bjorn, dear Linux folks,
Am 11.06.24 um 17:11 schrieb Bjorn Helgaas:
> On Mon, Jun 10, 2024 at 10:27:37PM +0200, Paul Menzel wrote:
>> Am 10.06.24 um 21:42 schrieb Bjorn Helgaas:
>>> On Sun, Jun 09, 2024 at 10:31:05AM +0200, Paul Menzel wrote:
>>>> On the servers below Linux warns:
>>>>
>>>> Unknown NUMA node; performance will be reduced
>>>
>>> This warning was added by ad5086108b9f ("PCI: Warn if no host bridge
>>> NUMA node info"), which appeared in v5.5, so I assume this isn't new.
>>>
>>> That commit log says:
>>>
>>> In pci_call_probe(), we try to run driver probe functions on the node where
>>> the device is attached. If we don't know which node the device is attached
>>> to, the driver will likely run on the wrong node. This will still work,
>>> but performance will not be as good as it could be.
>>>
>>> On NUMA systems, warn if we don't know which node a PCI host bridge is
>>> attached to. This is likely an indication that ACPI didn't supply a _PXM
>>> method or the DT didn't supply a "numa-node-id" property.
>>>
>>> I assume these are all ACPI systems, so likely missing _PXM. An
>>> acpidump could confirm this.
>>
>> I created an issue in the Linux Kernel Bugzilla [1] and attached the output
>> of `acpidump` on a Dell PowerEdge T630 there. The DSDT contains:
>>
>> Device (PCI1)
>> {
>> […]
>> Method (_PXM, 0, NotSerialized) // _PXM: Device Proximity
>> {
>> If ((CLOD == 0x00))
>> {
>> Return (0x01)
>> }
>> Else
>> {
>> Return (0x02)
>> }
>> }
>> […]
>> }
>
> This machine (the T630, from your first message) has several PCI host
> bridges:
>
> ACPI: PCI Root Bridge [UNC1] (domain 0000 [bus ff])
> pci_bus 0000:ff: root bus resource [bus ff]
>
> ACPI: PCI Root Bridge [UNC0] (domain 0000 [bus 7f])
> pci_bus 0000:7f: root bus resource [bus 7f]
>
> ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-7e])
> pci_bus 0000:00: root bus resource [io 0x0000-0x03bb window]
> pci_bus 0000:00: root bus resource [io 0x03bc-0x03df window]
> pci_bus 0000:00: root bus resource [io 0x03e0-0x0cf7 window]
> pci_bus 0000:00: root bus resource [io 0x1000-0x7fff window]
> pci_bus 0000:00: root bus resource [mem 0x000a0000-0x000bffff window]
> pci_bus 0000:00: root bus resource [mem 0x90000000-0xc7ffbfff window]
> pci_bus 0000:00: root bus resource [mem 0x38000000000-0x3bfffffffff window]
> pci_bus 0000:00: root bus resource [bus 00-7e]
>
> ACPI: PCI Root Bridge [PCI1] (domain 0000 [bus 80-fe])
> pci_bus 0000:80: root bus resource [io 0x8000-0xffff window]
> pci_bus 0000:80: root bus resource [mem 0xc8000000-0xfbffbfff window]
> pci_bus 0000:80: root bus resource [mem 0x3c000000000-0x3ffffffffff window]
> pci_bus 0000:80: root bus resource [bus 80-fe]
>
> PCI0 and PCI1 lead to all your normal PCI devices, they both
> implement _PXM, and they have all the usual apertures for PCI I/O and
> MMIO space where device BARs live.
>
> UNC0 and UNC1 lead to these special chipset devices, they don't
> implement _PXM, and they don't have any resources except the bus
> number. The devices on bus 7f and ff can only be used via config
> space accesses, and I have no idea what they are used for.
Maybe the X86 folks now.
Kind regards,
Paul
>> [1]: https://bugzilla.kernel.org/show_bug.cgi?id=218951
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