From c83040192f3763b243ece26073d61a895b4a230f Mon Sep 17 00:00:00 2001
From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Date: Wed, 1 Jul 2020 12:52:29 +0530
Subject: [PATCH] powerpc/pmem: Restrict papr_scm to P8 and above.
References: jsc#SLE-16402 jsc#SLE-16497 bsc#1176109 ltc#187964
Patch-mainline: v5.9-rc1
Git-commit: c83040192f3763b243ece26073d61a895b4a230f
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@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200701072235.223558-2-aneesh.kumar@linux.ibm.com
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
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;
--
2.28.0