From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (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 41VQ443bGMzF3Hx for ; Wed, 18 Jul 2018 02:00:52 +1000 (AEST) Received: from pps.filterd (m0098409.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w6HFxqbQ008164 for ; Tue, 17 Jul 2018 12:00:49 -0400 Received: from e33.co.us.ibm.com (e33.co.us.ibm.com [32.97.110.151]) by mx0a-001b2d01.pphosted.com with ESMTP id 2k9jmtjtdr-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 17 Jul 2018 12:00:46 -0400 Received: from localhost by e33.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 17 Jul 2018 10:00:35 -0600 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: [RESEND][PATCH] powerpc/powernv : Save/Restore SPRG3 on entry/exit from stop. Date: Tue, 17 Jul 2018 21:30:16 +0530 In-Reply-To: <1531826849-31838-1-git-send-email-ego@linux.vnet.ibm.com> References: <1531826849-31838-1-git-send-email-ego@linux.vnet.ibm.com> Message-Id: <1531843216-22209-1-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 saving the SPRN_SPRG3 before entering a deep stop state, and restoring it back on wakeup from the stop state. Fixes: e1c1cfed5432 ("powerpc/powernv: Save/Restore additional SPRs for stop4 cpuidle") 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