From 7104dccfd052fde51eecc9972dad9c40bd3e0d11 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Fri, 15 Feb 2019 20:20:20 +1000 Subject: [PATCH] powerpc/64s/hash: Fix assert_slb_presence() use of the slbfee. instruction The slbfee. instruction must have bit 24 of RB clear, failure to do so can result in false negatives that result in incorrect assertions. This is not obvious from the ISA v3.0B document, which only says: The hardware ignores the contents of RB 36:38 40:63 -- p.1032 This patch fixes the bug and also clears all other bits from PPC bit 36-63, which is good practice when dealing with reserved or ignored bits. Fixes: e15a4fea4dee ("powerpc/64s/hash: Add some SLB debugging tests") Cc: stable@vger.kernel.org # v4.20+ Reported-by: Aneesh Kumar K.V Tested-by: Aneesh Kumar K.V Signed-off-by: Nicholas Piggin Reviewed-by: Aneesh Kumar K.V Signed-off-by: Michael Ellerman --- arch/powerpc/mm/slb.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c index bc3914d54e26..5986df48359b 100644 --- a/arch/powerpc/mm/slb.c +++ b/arch/powerpc/mm/slb.c @@ -69,6 +69,11 @@ static void assert_slb_presence(bool present, unsigned long ea) if (!cpu_has_feature(CPU_FTR_ARCH_206)) return; + /* + * slbfee. requires bit 24 (PPC bit 39) be clear in RB. Hardware + * ignores all other bits from 0-27, so just clear them all. + */ + ea &= ~((1UL << 28) - 1); asm volatile(__PPC_SLBFEE_DOT(%0, %1) : "=r"(tmp) : "r"(ea) : "cr0"); WARN_ON(present == (tmp == 0));