Re: [PATCH] arm64: PCI: Validate the node before setting node id for root bus

[Baolin Wang <baolin.wang@linux.alibaba.com>]

Hi,

在 2020/9/28 23:23, Lorenzo Pieralisi 写道:
> On Mon, Sep 28, 2020 at 10:49:57PM +0800, Baolin Wang wrote:
>> On Mon, Sep 28, 2020 at 03:00:55PM +0100, Will Deacon wrote:
>>> [+ Lorenzo]
>>>
>>> On Tue, Sep 22, 2020 at 06:33:24PM +0800, Baolin Wang wrote:
>>>> If the BIOS disabled the NUMA configuration, but did not change the
>>>> proximity domain description in the SRAT table, so the PCI root bus
>>>> device may get a incorrect node id by acpi_get_node().
>>>
>>> How "incorrect" are we talking here? What actually goes wrong? At some
>>> point, we have to trust what the firmware is telling us.
>>
>> What I mean is, if we disable the NUMA from BIOS
> 
> Please define what this means ie are you removing SRAT from ACPI static
> tables ?

Yes.

> 
>> but we did not change the PXM for the PCI devices,
> 
> If a _PXM maps to a proximity domain that is not described in the SRAT
> your firmware is buggy.

Sorry for confusing, that's not what I mean. When the BIOS disable the 
NUMA (remove the SRAT table), but the PCI devices' _PXM description is 
still available, which means we can still get the pxm from 
acpi_evaluate_integer() in this case.

So we can get below inconsistent log on ARM platform:
"No NUMA configuration found
PCI_bus 0000:00 on NUMA node 0
...
PCI_bus 0000:e3 on NUMA node 1"

On X86, the pci_acpi_root_get_node() will validate the node before 
setting the node id for root bus. So I think we can add this validation 
for ARM platform. Or anything else I missed?

> 
>> so the PCI devices can still get a numa node id from acpi_get_node().
>> For example, we can still get the numa node id = 1 in this case from
>> acpi_get_node(), but the numa_nodes_parsed is empty, which means the
>> node id 1 is invalid.  We should add a validation for the node id when
>> setting the root bus node id.
> 
> The kernel is not a firmware validation test suite, so fix the firmware
> please.
> 
> Having said that, please provide a trace log of the issue this is
> causing, if any.

See above.