On Fri, May 03, 2019 at 06:24:04PM -0500, Jeremy Linton wrote: > ACPI 6.3 adds a flag to indicate that child nodes are all > identical cores. This is useful to authoritatively determine > if a set of (possibly offline) cores are identical or not. > > Since the flag doesn't give us a unique id we can generate > one and use it to create bitmaps of sibling nodes, or simply > in a loop to determine if a subset of cores are identical. > If possible reorder this patch with next just to be sure. I know the user is not introduced until 4/5, but 3/5 kind of fixes the implementation. Apart from that, this looks fine to me. Reviewed-by: Sudeep Holla <sudeep.holla@xxxxxxx> > Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx> > --- > drivers/acpi/pptt.c | 26 ++++++++++++++++++++++++++ > include/linux/acpi.h | 5 +++++ > 2 files changed, 31 insertions(+) > > diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c > index 83a026765faa..1865515297ca 100644 > --- a/drivers/acpi/pptt.c > +++ b/drivers/acpi/pptt.c > @@ -660,3 +660,29 @@ int find_acpi_cpu_topology_package(unsigned int cpu) > return find_acpi_cpu_topology_tag(cpu, PPTT_ABORT_PACKAGE, > ACPI_PPTT_PHYSICAL_PACKAGE); > } > + > +/** > + * find_acpi_cpu_topology_hetero_id() - Get a core architecture tag > + * @cpu: Kernel logical CPU number > + * > + * Determine a unique heterogeneous tag for the given CPU. CPUs with the same > + * implementation should have matching tags. > + * > + * The returned tag can be used to group peers with identical implementation. > + * > + * The search terminates when a level is found with the identical implementation > + * flag set or we reach a root node. > + * > + * Due to limitations in the PPTT data structure, there may be rare situations > + * where two cores in a heterogeneous machine may be identical, but won't have > + * the same tag. > + * Indeed, it's unfortunate. I gave some thoughts if we can find ways to avoid this. Hope we don't have to see such weird combinations with ACPI based systems. -- Regards, Sudeep
