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

[Baolin Wang]

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.