From: Desnes A. Nunes do Rosario desnesn@linux.ibm.com
commit fc37a1632d40c80c067eb1bc235139f5867a2667 upstream.
PowerVM systems running compatibility mode on a few Power8 revisions are still vulnerable to the hardware defect that loses PMU exceptions arriving prior to a context switch.
The software fix for this issue is enabled through the CPU_FTR_PMAO_BUG cpu_feature bit, nevertheless this bit also needs to be set for PowerVM compatibility mode systems.
Fixes: 68f2f0d431d9ea4 ("powerpc: Add a cpu feature CPU_FTR_PMAO_BUG") Signed-off-by: Desnes A. Nunes do Rosario desnesn@linux.ibm.com Reviewed-by: Leonardo Bras leonardo@linux.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20200227134715.9715-1-desnesn@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/kernel/cputable.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/arch/powerpc/kernel/cputable.c +++ b/arch/powerpc/kernel/cputable.c @@ -2147,11 +2147,13 @@ static struct cpu_spec * __init setup_cp * oprofile_cpu_type already has a value, then we are * possibly overriding a real PVR with a logical one, * and, in that case, keep the current value for - * oprofile_cpu_type. + * oprofile_cpu_type. Futhermore, let's ensure that the + * fix for the PMAO bug is enabled on compatibility mode. */ if (old.oprofile_cpu_type != NULL) { t->oprofile_cpu_type = old.oprofile_cpu_type; t->oprofile_type = old.oprofile_type; + t->cpu_features |= old.cpu_features & CPU_FTR_PMAO_BUG; } }