From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 41Vr5L3vmHzF35L for ; Wed, 18 Jul 2018 18:33:26 +1000 (AEST) Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w6I8UQe4077043 for ; Wed, 18 Jul 2018 04:33:24 -0400 Received: from e15.ny.us.ibm.com (e15.ny.us.ibm.com [129.33.205.205]) by mx0b-001b2d01.pphosted.com with ESMTP id 2k9xj6rhd2-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 18 Jul 2018 04:33:24 -0400 Received: from localhost by e15.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 18 Jul 2018 04:33:23 -0400 From: "Gautham R. Shenoy" To: Michael Ellerman , Benjamin Herrenschmidt , Michael Neuling , Vaidyanathan Srinivasan Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Florian Weimer , "Gautham R. Shenoy" , , Oleg Nesterov Subject: [PATCH v2] powerpc/powernv : Save/Restore SPRG3 on entry/exit from stop. Date: Wed, 18 Jul 2018 14:03:16 +0530 Message-Id: <1531902796-32294-1-git-send-email-ego@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: "Gautham R. Shenoy" On 64-bit servers, SPRN_SPRG3 and its userspace read-only mirror SPRN_USPRG3 are used as userspace VDSO write and read registers respectively. SPRN_SPRG3 is lost when we enter stop4 and above, and is currently not restored. As a result, any read from SPRN_USPRG3 returns zero on an exit from stop4 and above. Thus in this situation, on POWER9, any call from sched_getcpu() always returns zero, as on powerpc, we call __kernel_getcpu() which relies upon SPRN_USPRG3 to report the CPU and NUMA node information. Fix this by restoring SPRN_SPRG3 on wake up from a deep stop state with the sprg_vdso value that is cached in PACA. Fixes: e1c1cfed5432 ("powerpc/powernv: Save/Restore additional SPRs for stop4 cpuidle") Reported-by: Florian Weimer Cc: # 4.14 Cc: Oleg Nesterov Cc: Michael Neuling Cc: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Vaidyanathan Srinivasan Signed-off-by: Gautham R. Shenoy --- Change from v1: Restoring the SPRG3 from paca->sprg_vdso instead of saving it separately during stop-entry, as suggested by Mikey. arch/powerpc/kernel/idle_book3s.S | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S index d85d551..672ead8 100644 --- a/arch/powerpc/kernel/idle_book3s.S +++ b/arch/powerpc/kernel/idle_book3s.S @@ -144,7 +144,9 @@ power9_restore_additional_sprs: mtspr SPRN_MMCR1, r4 ld r3, STOP_MMCR2(r13) + ld r4, PACA_SPRG_VDSO(r13) mtspr SPRN_MMCR2, r3 + mtspr SPRN_SPRG3, r4 blr /* -- 1.8.3.1