From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:46688 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726943AbeGWIxt (ORCPT ); Mon, 23 Jul 2018 04:53:49 -0400 Date: Mon, 23 Jul 2018 09:53:50 +0200 From: Greg KH To: "Gautham R. Shenoy" Cc: stable@vger.kernel.org, Michael Ellerman Subject: Re: [PATCH] powerpc/powernv : Save/Restore SPRG3 on entry/exit from stop. Message-ID: <20180723075350.GA31879@kroah.com> References: <1532277223142142@kroah.com> <1532323855-25307-1-git-send-email-ego@linux.vnet.ibm.com> <20180723061628.GA2035@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180723061628.GA2035@kroah.com> Sender: stable-owner@vger.kernel.org List-ID: On Mon, Jul 23, 2018 at 08:16:28AM +0200, Greg KH wrote: > On Mon, Jul 23, 2018 at 11:00:55AM +0530, Gautham R. Shenoy wrote: > > From: "Gautham R. Shenoy" > > > > [ Upstream commit b03897cf318dfc47de33a7ecbc7655584266f034 ] > > > > 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 > > Signed-off-by: Gautham R. Shenoy > > Reviewed-by: Michael Ellerman > > Signed-off-by: Michael Ellerman > > --- > > arch/powerpc/kernel/idle_book3s.S | 2 ++ > > 1 file changed, 2 insertions(+) > > What stable tree(s) do you want this applied to? I've now guessed that it is 4.14.y. If that's not the case, please let me know. greg k-h