[PATCH v4 1/8] powerpc/pmem: Restrict papr_scm to P8 and above.

The PAPR based virtualized persistent memory devices are only supported on POWER9 and above. In the followup patch, the kernel will switch the persistent memory cache flush functions to use a new `dcbf` variant instruction. The new instructions even though added in ISA 3.1 works even on P8 and P9 because these are implemented as a variant of existing `dcbf` and `hwsync` and on P8 and P9 behaves as such. Considering these devices are only supported on P8 and above, update the driver to prevent a P7-compat guest from using persistent memory devices. We don't update of_pmem driver with the same condition, because, on bare-metal, the firmware enables pmem support only on P9 and above. There the kernel depends on OPAL firmware to restrict exposing persistent memory related device tree entries on older hardware. of_pmem.ko is written without any arch dependency and we don't want to add ppc64 specific cpu feature check in of_pmem driver. Signed-off-by: Aneesh Kumar K.V <aneesh.kumar(a)linux.ibm.com&gt; --- arch/powerpc/platforms/pseries/pmem.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/powerpc/platforms/pseries/pmem.c b/arch/powerpc/platforms/pseries/pmem.c index f860a897a9e0..2347e1038f58 100644 --- a/arch/powerpc/platforms/pseries/pmem.c +++ b/arch/powerpc/platforms/pseries/pmem.c @@ -147,6 +147,12 @@ const struct of_device_id drc_pmem_match[] = { static int pseries_pmem_init(void) { + /* + * Only supported on POWER8 and above. + */ + if (!cpu_has_feature(CPU_FTR_ARCH_207S)) + return 0; + pmem_node = of_find_node_by_type(NULL, "ibm,persistent-memory"); if (!pmem_node) return 0; -- 2.26.2