[PATCH v3 05/12] arm64, acpi, numa: NUMA support based on SRAT and SLIT

Robert Richter
2016-01-27T14:01:09Z

On 27.01.16 15:12:15, Hanjun Guo wrote:
> On 2016/1/25 18:21, Robert Richter wrote:
> > On 23.01.16 17:39:20, Hanjun Guo wrote:
> >> diff --git a/arch/arm64/kernel/acpi_numa.c b/arch/arm64/kernel/acpi_numa.c
> >> new file mode 100644
> >> index 0000000..f7f7533
> >> --- /dev/null
> >> +++ b/arch/arm64/kernel/acpi_numa.c
> >> +/* Callback for parsing of the Proximity Domain <-> Memory Area mappings */
> >> +int __init acpi_numa_memory_affinity_init(struct acpi_srat_mem_affinity *ma)
> >> +{
> >> + u64 start, end;
> >> + int node, pxm;
> >> +
> >> + if (srat_disabled())
> >> + return -EINVAL;
> >> +
> >> + if (ma->header.length != sizeof(struct acpi_srat_mem_affinity)) {
> > Must be:
> >
> > ma->header.length < sizeof(struct acpi_srat_mem_affinity)) {
> >
> > Allow extensions to struct acpi_srat_mem_affinity in newer versions.
>
> Hmm, I think we need to remove the check here now.

No, we might have an out-of-bound access then.

>
> There are three cases:
>
> - firmware ACPI version is consistent with the ACPICA one, then
> ma->header.length == sizeof(struct acpi_srat_mem_affinity )
>
> - firmware ACPI version is not consistent with the ACPICA one,
> for example, struct acpi_srat_mem_affinity is extended in
> new ACI version, but the formware is using the older one,
> then it's ok to use
> ma->header.length < sizeof(struct acpi_srat_mem_affinity )

The check above is ok as we need@least struct
acpi_srat_mem_affinity as it is now.

If we later change the kernel to support multiple versions of struct
acpi_srat_mem_affinity, i.e. use data from an extended section, we
will need to add code to handle that. This will include support of
data with length < acpi_srat_mem_affinity, in this case we may not use
extended data.

>
> - but if we use the older kernel + updated new firmware,
> then
> ma->header.length > sizeof(struct acpi_srat_mem_affinity )
> will be the case, right?

Right, and this is a valid case not resulting in an error with my
suggestion above.

>
> >
> >> + bad_srat();
> >> + return -EINVAL;
> > We need a pr_err() here to avoid that numa setup fails silently due to
> > bad fw. This applies to all error paths.
> >
> > See my delta patch below. You can merge it with your patch.
>
> Thanks! I wil merge it into next version.

Thanks,

-Robert