From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:39210 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030648AbdEWOvY (ORCPT ); Tue, 23 May 2017 10:51:24 -0400 Subject: Patch "powerpc/book3s/mce: Move add_taint() later in virtual mode" has been added to the 4.9-stable tree To: mahesh@linux.vnet.ibm.com, gregkh@linuxfoundation.org, mpe@ellerman.id.au Cc: , From: Date: Tue, 23 May 2017 16:48:47 +0200 Message-ID: <14955509272440@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled powerpc/book3s/mce: Move add_taint() later in virtual mode to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: powerpc-book3s-mce-move-add_taint-later-in-virtual-mode.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From d93b0ac01a9ce276ec39644be47001873d3d183c Mon Sep 17 00:00:00 2001 From: Mahesh Salgaonkar Date: Tue, 18 Apr 2017 22:08:17 +0530 Subject: powerpc/book3s/mce: Move add_taint() later in virtual mode From: Mahesh Salgaonkar commit d93b0ac01a9ce276ec39644be47001873d3d183c upstream. machine_check_early() gets called in real mode. The very first time when add_taint() is called, it prints a warning which ends up calling opal call (that uses OPAL_CALL wrapper) for writing it to console. If we get a very first machine check while we are in opal we are doomed. OPAL_CALL overwrites the PACASAVEDMSR in r13 and in this case when we are done with MCE handling the original opal call will use this new MSR on it's way back to opal_return. This usually leads to unexpected behaviour or the kernel to panic. Instead move the add_taint() call later in the virtual mode where it is safe to call. This is broken with current FW level. We got lucky so far for not getting very first MCE hit while in OPAL. But easily reproducible on Mambo. Fixes: 27ea2c420cad ("powerpc: Set the correct kernel taint on machine check errors.") Signed-off-by: Mahesh Salgaonkar Signed-off-by: Michael Ellerman Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/mce.c | 2 ++ arch/powerpc/kernel/traps.c | 4 ++-- 2 files changed, 4 insertions(+), 2 deletions(-) --- a/arch/powerpc/kernel/mce.c +++ b/arch/powerpc/kernel/mce.c @@ -205,6 +205,8 @@ static void machine_check_process_queued { int index; + add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE); + /* * For now just print it to console. * TODO: log this error event to FSP or nvram. --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -302,8 +302,6 @@ long machine_check_early(struct pt_regs __this_cpu_inc(irq_stat.mce_exceptions); - add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE); - if (cur_cpu_spec && cur_cpu_spec->machine_check_early) handled = cur_cpu_spec->machine_check_early(regs); return handled; @@ -737,6 +735,8 @@ void machine_check_exception(struct pt_r __this_cpu_inc(irq_stat.mce_exceptions); + add_taint(TAINT_MACHINE_CHECK, LOCKDEP_NOW_UNRELIABLE); + /* See if any machine dependent calls. In theory, we would want * to call the CPU first, and call the ppc_md. one if the CPU * one returns a positive number. However there is existing code Patches currently in stable-queue which might be from mahesh@linux.vnet.ibm.com are queue-4.9/powerpc-book3s-mce-move-add_taint-later-in-virtual-mode.patch