Re: [PATCH v3] NUMA x86: add constraints check for nid parameters

From: David Rientjes
Date: Fri Dec 09 2011 - 05:44:22 EST


On Fri, 9 Dec 2011, Ingo Molnar wrote:

> Thanks guys.
>
> Just to double check: there's no known instance of such a bad
> SRAT in existence, so this commit can wait until v3.3 and does
> hot have to go into v3.2, right?
>

Andi mentioned buggy SRATs, but it's outside the scope of this patch; this
has nothing to do with buggy SRATs.

Ignoring NUMA emulation which plays with these when you boot with
numa=fake, this patch is catching any instance where pxm_to_node(x)
returns NUMA_NO_NODE, meaning x is not an initialized pxm. For x86, we
initialize pxms by grabbing them from the SRAT, picking the first unused
node id, and mapping them. The SRAT has nothing to do with this, the ACPI
spec has no notion of what we've defined a node to be. So Petr's patch
will simply catch any instance of pxm_to_node(x) where x was not
initialized and incorrectly referencing
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