From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752100AbdEPIuj (ORCPT ); Tue, 16 May 2017 04:50:39 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:54018 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751946AbdEPIuG (ORCPT ); Tue, 16 May 2017 04:50:06 -0400 From: "Gautham R. Shenoy" To: Nicholas Piggin , Michael Ellerman , Michael Neuling , Vaidyanathan Srinivasan , Shilpasri G Bhat , Akshay Adiga , Benjamin Herrenschmidt Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, "Gautham R. Shenoy" Subject: [PATCH 1/6] powernv:idle: Correctly initialize core_idle_state_ptr Date: Tue, 16 May 2017 14:19:43 +0530 X-Mailer: git-send-email 1.8.3.1 In-Reply-To: References: In-Reply-To: References: X-TM-AS-GCONF: 00 x-cbid: 17051608-0028-0000-0000-000007991309 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00007070; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000212; SDB=6.00861181; UDB=6.00427105; IPR=6.00640844; BA=6.00005351; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00015477; XFM=3.00000015; UTC=2017-05-16 08:50:04 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17051608-0029-0000-0000-000035C610BD Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-05-16_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1703280000 definitions=main-1705160077 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Gautham R. Shenoy" 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 --- 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 445f30a..84eb9bc 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 *)); -- 1.8.3.1