From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:41070 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387882AbeGWHQH (ORCPT ); Mon, 23 Jul 2018 03:16:07 -0400 Date: Mon, 23 Jul 2018 08:16:28 +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: <20180723061628.GA2035@kroah.com> References: <1532277223142142@kroah.com> <1532323855-25307-1-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: <1532323855-25307-1-git-send-email-ego@linux.vnet.ibm.com> Sender: stable-owner@vger.kernel.org List-ID: 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? thanks, greg k-h