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

[Baolin Wang]

> On Tue, Sep 29, 2020 at 11:41:29PM +0800, Baolin Wang wrote:
> > Hi,
> >
> > 锟斤拷 2020/9/28 23:23, Lorenzo Pieralisi 写锟斤拷:
> > > 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.
>
> There should not be a _PXM object if the SRAT is not available, that's
> a firmware bug.
>
> > 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?
>
> We are not adding checks because x86 does it, it is certainly to paper
> over a firmware bug that you hopefully still have a chance to fix,
> let's do that instead of adding code that is not necessary.

Thanks for your input, and I will check this issue with our firmware 
colleagues again.