From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:45632 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388345AbeGWN3V (ORCPT ); Mon, 23 Jul 2018 09:29:21 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Florian Weimer , "Gautham R. Shenoy" , Michael Ellerman Subject: [PATCH 4.17 28/63] powerpc/powernv: Fix save/restore of SPRG3 on entry/exit from stop (idle) Date: Mon, 23 Jul 2018 14:24:34 +0200 Message-Id: <20180723122447.440157611@linuxfoundation.org> In-Reply-To: <20180723122446.351334162@linuxfoundation.org> References: <20180723122446.351334162@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gautham R. Shenoy commit b03897cf318dfc47de33a7ecbc7655584266f034 upstream. 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 (Power9 only) 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") Cc: stable@vger.kernel.org # v4.14+ Reported-by: Florian Weimer Signed-off-by: Gautham R. Shenoy Reviewed-by: Michael Ellerman Signed-off-by: Michael Ellerman Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/idle_book3s.S | 2 ++ 1 file changed, 2 insertions(+) --- 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 /*