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

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Date:   Mon, 28 Sep 2020 16:23:26 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc:     Will Deacon <will@...nel.org>, catalin.marinas@....com,
        baolin.wang7@...il.com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: PCI: Validate the node before setting node id for
 root bus

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 ?

> 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.

> 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.

Thanks,
Lorenzo