From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1951AC677FC for ; Thu, 11 Oct 2018 17:49:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CDC002085B for ; Thu, 11 Oct 2018 17:49:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CDC002085B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-pci-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728642AbeJLBRU (ORCPT ); Thu, 11 Oct 2018 21:17:20 -0400 Received: from mga14.intel.com ([192.55.52.115]:26293 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727693AbeJLBRU (ORCPT ); Thu, 11 Oct 2018 21:17:20 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Oct 2018 10:49:04 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,369,1534834800"; d="scan'208";a="78055880" Received: from unknown (HELO localhost.localdomain) ([10.232.112.69]) by fmsmga008.fm.intel.com with ESMTP; 11 Oct 2018 10:48:16 -0700 Date: Thu, 11 Oct 2018 11:45:16 -0600 From: Keith Busch To: Bjorn Helgaas Cc: linux-pci@vger.kernel.org Subject: Re: [PATCH 3/3] PCI/AER: Covertly inject errors with ftrace hooks Message-ID: <20181011174516.GE11034@localhost.localdomain> References: <20181011165207.12782-1-keith.busch@intel.com> <20181011165207.12782-4-keith.busch@intel.com> <20181011170826.GR5906@bhelgaas-glaptop.roam.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181011170826.GR5906@bhelgaas-glaptop.roam.corp.google.com> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Thu, Oct 11, 2018 at 12:08:26PM -0500, Bjorn Helgaas wrote: > On Thu, Oct 11, 2018 at 10:52:07AM -0600, Keith Busch wrote: > > The aer_inject module had been intercepting config requests by overwriting > > the config accessor operations in the pci_bus ops. This has several > > issues. > > > > First, the module was tracking kernel objects unbeknownst to the drivers > > that own them. The kernel may free those devices, leaving the AER inject > > module holding stale references and no way to know that happened. > > > > Second, the PCI enumeration has child devices inherit pci_bus ops from > > the parent bus. Since errors may lead to link resets that trigger > > re-enumeration, the child devices would inherit operations that don't > > know about the devices using them, causing kernel crashes. > > > > Finally, CONFIG_PCI_LOCKLESS_CONFIG doesn't block accessing the pci_bus > > ops, so it's racing with potential in-flight config requests. > > > > This patch uses a different error injection approach leveraging ftrace > > to thunk the config space functions. If the kernel and architecture > > are capable, the ftrace hook will overwrite the processor's function > > call address with the address of the error injecting function. This way > > doesn't modify or track driver structures, fixing the issues with the > > current method. > > > > If either the kernel config or platform arch do not support the necessary > > ftrace capabilities, the aer_inject module will fallback to the older > > way so that it may continue to be used as before. > > > > Signed-off-by: Keith Busch > > --- > > drivers/pci/pcie/aer_inject.c | 218 ++++++++++++++++++++++++++++++++++++------ > > 1 file changed, 189 insertions(+), 29 deletions(-) > > > > diff --git a/drivers/pci/pcie/aer_inject.c b/drivers/pci/pcie/aer_inject.c > > index 726987f8d53c..4825fa465b60 100644 > > --- a/drivers/pci/pcie/aer_inject.c > > +++ b/drivers/pci/pcie/aer_inject.c > > > +static int aer_inj_legacy_read(struct pci_bus *bus, unsigned int devfn, > > + int where, int size, u32 *val) > > +{ > > + struct pci_ops *ops, *my_ops; > > + int rv; > > + > > + ops = __find_pci_bus_ops(bus); > > + if (!ops) > > + return -1; > > + > > + my_ops = bus->ops; > > + bus->ops = ops; > > + rv = ops->read(bus, devfn, where, size, val); > > + bus->ops = my_ops; > > + > > + return rv; > > +} > > + > > +static int aer_inj_legacy_write(struct pci_bus *bus, unsigned int devfn, > > + int where, int size, u32 val) > > +{ > > + struct pci_ops *ops, *my_ops; > > + int rv; > > + > > + ops = __find_pci_bus_ops(bus); > > + if (!ops) > > + return -1; > > + > > + my_ops = bus->ops; > > + bus->ops = ops; > > + rv = ops->write(bus, devfn, where, size, val); > > + bus->ops = my_ops; > > + > > + return rv; > > +} > > Is there any chance you could split this into two (or more) patches? > > The part above looks like pretty straightforward code movement without > any functional change. It would be nice to get that part out of the way, > then have a smaller patch that adds the fancy ftrace stuff. No problem, will do.