[PATCH v2] powerpc/book3s64/pkey: Disable pkey on POWER6 and before

POWER6 only support AMR update via privileged mode(MSR[PR] = 0, SPRN_AMR=29)
The PR=1 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 check for P7 CPU_FTR bit to decide on pkey support.

Fixes: a24204c30796 ("powerpc/book3s64/pkeys: kill cpu feature key CPU_FTR_PKEY")
Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Aneesh Kumar K.V <redacted>
---
 arch/powerpc/mm/book3s64/pkeys.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/powerpc/mm/book3s64/pkeys.c b/arch/powerpc/mm/book3s64/pkeys.c
index 792b36aa9619..69a6b87f2bb4 100644
--- 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) {
 		/*

-- 
2.26.2

On Sun, 26 Jul 2020 18:55:17 +0530, Aneesh Kumar K.V wrote:

POWER6 only support AMR update via privileged mode(MSR[PR] = 0, SPRN_AMR=29)
The PR=1 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 check for P7 CPU_FTR bit to decide on pkey support.

Applied to powerpc/next.

[1/1] powerpc/book3s64/pkey: Disable pkey on POWER6 and before
      https://git.kernel.org/powerpc/c/269e829f48a0d0d27667abe25ca5c9e5b6ab08e2

cheers