From 5f221c3ca13dceaea8eefe21dbd85da91ed9b1e8 Mon Sep 17 00:00:00 2001 From: "Gautham R. Shenoy" Date: Tue, 16 May 2017 14:19:43 +0530 Subject: [PATCH] powerpc/powernv/idle: Correctly initialize core_idle_state_ptr 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 Signed-off-by: Michael Ellerman --- arch/powerpc/platforms/powernv/idle.c | 29 ++++++++++++++++++--------- 1 file changed, 19 insertions(+), 10 deletions(-) diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c index 0c21747ed7e0..502f3275d8c2 100644 --- a/arch/powerpc/platforms/powernv/idle.c +++ b/arch/powerpc/platforms/powernv/idle.c @@ -96,15 +96,24 @@ static void pnv_alloc_idle_core_states(void) u32 *core_idle_state; /* - * core_idle_state - First 8 bits track the idle state of each thread - * of the core. The 8th bit is the lock bit. Initially all thread bits - * are set. They are cleared when the thread enters deep idle state - * like sleep and winkle. Initially the lock bit is cleared. - * The lock bit has 2 purposes - * a. While the first thread is restoring core state, it prevents - * other threads in the core from switching to process context. - * b. While the last thread in the core is saving the core state, it - * prevents a different thread from waking up. + * core_idle_state - The lower 8 bits track the idle state of + * each thread of the core. + * + * The most significant bit is the lock bit. + * + * Initially all the bits corresponding to threads_per_core + * are set. They are cleared when the thread enters deep idle + * state like sleep and winkle/stop. + * + * Initially the lock bit is cleared. The lock bit has 2 + * purposes: + * a. While the first thread in the core waking up from + * idle is restoring core state, it prevents other + * threads in the core from switching to process + * context. + * b. While the last thread in the core is saving the + * core state, it prevents a different thread from + * waking up. */ for (i = 0; i < nr_cores; i++) { int first_cpu = i * threads_per_core; @@ -112,7 +121,7 @@ static void pnv_alloc_idle_core_states(void) size_t paca_ptr_array_size; core_idle_state = kmalloc_node(sizeof(u32), GFP_KERNEL, node); - *core_idle_state = PNV_CORE_IDLE_THREAD_BITS; + *core_idle_state = (1 << threads_per_core) - 1; paca_ptr_array_size = (threads_per_core * sizeof(struct paca_struct *)); -- GitLab