powerpc/book3s64/pkey: Disable pkey on POWER6 and before

POWER6 only supports AMR update via privileged mode (MSR[PR] = 0,
SPRN_AMR=29) The PR=1 (userspace) alias for that SPR (SPRN_AMR=13) was
only supported from POWER7. Since we don't allow userspace modifying
of AMR value we should disable pkey support on P6 and before.

The hypervisor will still report pkey support via
"ibm,processor-storage-keys". Hence also check for P7 CPU_FTR bit to
decide on pkey support.

Fixes: f491fe3fb41e ("powerpc/book3s64/pkeys: Simplify the key initialization")
Reported-by: Michael Ellerman <mpe@ellerman.id.au>
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/20200726132517.399076-1-aneesh.kumar@linux.ibm.com

diff --git a/arch/powerpc/mm/book3s64/pkeys.c b/arch/powerpc/mm/book3s64/pkeys.c
index 792b36aa9619e184add4ffba31607f9b3a346c49..69a6b87f2bb4e384a6892f1fa2ee5858af8de9fb 100644 (file)
--- a/arch/powerpc/mm/book3s64/pkeys.c
+++ b/arch/powerpc/mm/book3s64/pkeys.c
@@ -73,6 +73,12 @@ static int scan_pkey_feature(void)
        if (early_radix_enabled())
                return 0;
 
+       /*
+        * Only P7 and above supports SPRN_AMR update with MSR[PR] = 1
+        */
+       if (!early_cpu_has_feature(CPU_FTR_ARCH_206))
+               return 0;
+
        ret = of_scan_flat_dt(dt_scan_storage_keys, &pkeys_total);
        if (ret == 0) {
                /*