On Tue, 16 May 2017 14:19:43 +0530
"Gautham R. Shenoy" [off-list ref] wrote:

From: "Gautham R. Shenoy" <redacted>

The lower 8 bits of core_idle_state_ptr tracks the number of non-idle
threads in the core. This is supposed to be initialized to bit-map
corresponding to the threads_per_core. However, currently it is
initialized to PNV_CORE_IDLE_THREAD_BITS (0xFF). This is correct for
POWER8 which has 8 threads per core, but not for POWER9 which has 4
threads per core.

As a result, on POWER9, core_idle_state_ptr gets initialized to
0xFF. In case when all the threads of the core are idle, the bits
corresponding tracking the idle-threads are non-zero. As a result, the
idle entry/exit code fails to save/restore per-core hypervisor state
since it assumes that there are threads in the cores which are still
active.

Fix this by correctly initializing the lower bits of the
core_idle_state_ptr on the basis of threads_per_core.

Signed-off-by: Gautham R. Shenoy <redacted>

This looks good to me.

Until this patch series, we can't enable HV state loss idle modes
on POWER9, is that correct? And after your series does it work?

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>