From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D7F8CECDFB1 for ; Tue, 17 Jul 2018 11:47:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9A07B20C09 for ; Tue, 17 Jul 2018 11:47:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9A07B20C09 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.vnet.ibm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731252AbeGQMTq (ORCPT ); Tue, 17 Jul 2018 08:19:46 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:60124 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730444AbeGQMTq (ORCPT ); Tue, 17 Jul 2018 08:19:46 -0400 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w6HBi2Qx128508 for ; Tue, 17 Jul 2018 07:47:30 -0400 Received: from e17.ny.us.ibm.com (e17.ny.us.ibm.com [129.33.205.207]) by mx0a-001b2d01.pphosted.com with ESMTP id 2k9fjp0t05-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 17 Jul 2018 07:47:30 -0400 Received: from localhost by e17.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 17 Jul 2018 07:47:25 -0400 Received: from b01ledav001.gho.pok.ibm.com (b01ledav001.gho.pok.ibm.com [9.57.199.106]) by b01cxnp22036.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w6HBlOwx1245638 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 17 Jul 2018 11:47:24 GMT Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 956AA2805A; Tue, 17 Jul 2018 07:46:40 -0400 (EDT) Received: from b01ledav001.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 2223D28058; Tue, 17 Jul 2018 07:46:40 -0400 (EDT) Received: from sofia.ibm.com (unknown [9.124.35.39]) by b01ledav001.gho.pok.ibm.com (Postfix) with ESMTP; Tue, 17 Jul 2018 07:46:40 -0400 (EDT) Received: by sofia.ibm.com (Postfix, from userid 1000) id 570F42E2F57; Tue, 17 Jul 2018 17:17:22 +0530 (IST) Date: Tue, 17 Jul 2018 17:17:22 +0530 From: Gautham R Shenoy To: "Gautham R. Shenoy" Cc: Michael Ellerman , Benjamin Herrenschmidt , Michael Neuling , Vaidyanathan Srinivasan , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Florian Weimer , Oleg Nesterov Subject: Re: [PATCH] powerpc/powernv : Save/Restore SPRG3 on entry/exit from stop. Reply-To: ego@linux.vnet.ibm.com References: <1531826849-31838-1-git-send-email-ego@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1531826849-31838-1-git-send-email-ego@linux.vnet.ibm.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-TM-AS-GCONF: 00 x-cbid: 18071711-0040-0000-0000-0000044FFFB3 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009379; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000266; SDB=6.01062049; UDB=6.00545287; IPR=6.00839954; MB=3.00022167; MTD=3.00000008; XFM=3.00000015; UTC=2018-07-17 11:47:28 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18071711-0041-0000-0000-000008562A2B Message-Id: <20180717114722.GA27570@in.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-07-17_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1806210000 definitions=main-1807170123 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 17, 2018 at 04:57:29PM +0530, Gautham R. Shenoy wrote: > 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, any call from sched_getcpu() always returns This happens only on POWER9. > zero, as on powerpc, we call __kernel_getcpu() which relies upon > SPRN_USPRG3 to report the CPU and NUMA node information. > > Fix this by saving the SPRN_SPRG3 before entering a deep stop state, > and restoring it back on wakeup from the stop state. > I forgot to add that this fixes commit e1c1cfed5432 ("powerpc/powernv: Save/Restore additional SPRs for stop4 cpuidle"). @mpe, do you want me to send fresh patch with these updates ? > Reported-by: Florian Weimer > Cc: Oleg Nesterov > Cc: Michael Neuling > Cc: Michael Ellerman > Cc: Benjamin Herrenschmidt > Cc: Vaidyanathan Srinivasan > Signed-off-by: Gautham R. Shenoy > --- > arch/powerpc/include/asm/cpuidle.h | 1 + > arch/powerpc/kernel/asm-offsets.c | 1 + > arch/powerpc/kernel/idle_book3s.S | 5 +++++ > 3 files changed, 7 insertions(+) > > diff --git a/arch/powerpc/include/asm/cpuidle.h b/arch/powerpc/include/asm/cpuidle.h > index e210a83..03fa904 100644 > --- a/arch/powerpc/include/asm/cpuidle.h > +++ b/arch/powerpc/include/asm/cpuidle.h > @@ -77,6 +77,7 @@ struct stop_sprs { > u64 mmcr1; > u64 mmcr2; > u64 mmcra; > + u64 sprg3; > }; > > extern u32 pnv_fastsleep_workaround_at_entry[]; > diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c > index 89cf155..a35ebfc 100644 > --- a/arch/powerpc/kernel/asm-offsets.c > +++ b/arch/powerpc/kernel/asm-offsets.c > @@ -776,6 +776,7 @@ int main(void) > STOP_SPR(STOP_MMCR1, mmcr1); > STOP_SPR(STOP_MMCR2, mmcr2); > STOP_SPR(STOP_MMCRA, mmcra); > + STOP_SPR(STOP_SPRG3, sprg3); > #endif > > DEFINE(PPC_DBELL_SERVER, PPC_DBELL_SERVER); > diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S > index d85d551..5069d42 100644 > --- a/arch/powerpc/kernel/idle_book3s.S > +++ b/arch/powerpc/kernel/idle_book3s.S > @@ -120,6 +120,9 @@ power9_save_additional_sprs: > mfspr r4, SPRN_MMCR2 > std r3, STOP_MMCR1(r13) > std r4, STOP_MMCR2(r13) > + > + mfspr r3, SPRN_SPRG3 > + std r3, STOP_SPRG3(r13) > blr > > power9_restore_additional_sprs: > @@ -144,7 +147,9 @@ power9_restore_additional_sprs: > mtspr SPRN_MMCR1, r4 > > ld r3, STOP_MMCR2(r13) > + ld r4, STOP_SPRG3(r13) > mtspr SPRN_MMCR2, r3 > + mtspr SPRN_SPRG3, r4 > blr > > /* > -- > 1.9.4 >