linux-kernel - Re: [PATCH 00/12] error handling and pciehp maintenance

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Date:   Fri, 5 Oct 2018 12:31:45 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Keith Busch <keith.busch@...el.com>
Cc:     Linux PCI <linux-pci@...r.kernel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Sinan Kaya <okaya@...nel.org>,
        Thomas Tai <thomas.tai@...cle.com>, poza@...eaurora.org,
        Lukas Wunner <lukas@...ner.de>, Christoph Hellwig <hch@....de>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/12] error handling and pciehp maintenance

[+cc arm64 folks, LKML: This conversation is about this patch:

  https://lore.kernel.org/linux-pci/20180918235848.26694-3-keith.busch@intel.com

which fixes some PCIe AER error injection bugs, but also makes the error
injector dependent on DYNAMIC_FTRACE_WITH_REGS, which not all arches
support.  Note that this question is only about the error *injection*
module used for testing.  It doesn't affect AER support itself.]

On Thu, Oct 04, 2018 at 04:11:37PM -0600, Keith Busch wrote:
> On Thu, Oct 04, 2018 at 04:40:15PM -0500, Bjorn Helgaas wrote:
> > On Tue, Sep 18, 2018 at 05:58:36PM -0600, Keith Busch wrote:
> > > I ran into a lot of trouble testing error handling, and this series is
> > > just trying to simplify some things. The first 4 fix up aer_inject, and
> > > the rest are cleanup to make better use of kernel APIs.
> > > 
> > > Keith Busch (12):
> > >   PCI: Set PCI bus accessors to noinline
> > >   PCI/AER: Covertly inject errors
> > >   PCI/AER: Reuse existing service device lookup
> > >   PCI/AER: Abstract AER interrupt handling
> > >   PCI/AER: Remove dead code
> > >   PCI/AER: Remove error source from aer struct
> > >   PCI/AER: Use kfifo for tracking events
> > >   PCI/AER: Use kfifo helper inserting locked elements
> > >   PCI/AER: Don't read upstream ports below fatal errors
> > >   PCI/AER: Use threaded IRQ for bottom half
> > >   PCI/AER: Use managed resource allocations
> > >   PCI/pciehp: Use device managed allocations
> > > 
> > >  drivers/pci/access.c              |   4 +-
> > >  drivers/pci/hotplug/pciehp_core.c |  14 +-
> > >  drivers/pci/hotplug/pciehp_hpc.c  |  48 ++----
> > >  drivers/pci/pcie/Kconfig          |   2 +-
> > >  drivers/pci/pcie/aer.c            | 219 ++++++---------------------
> > >  drivers/pci/pcie/aer_inject.c     | 306 ++++++++++++++++++++------------------
> > >  drivers/pci/pcie/portdrv.h        |   4 -
> > >  drivers/pci/pcie/portdrv_core.c   |   1 +
> > >  8 files changed, 227 insertions(+), 371 deletions(-)
> > 
> > Thanks a lot for doing this!  I applied these to pci/hotplug for
> > v4.20, except for "PCI/AER: Don't read upstream ports below fatal
> > errors", which seems to be already there via another posting, and
> > "PCI/pciehp: Use device managed allocations", which needs a few
> > tweaks.
> 
> Sounds good, and thanks for applying!
> 
> In case this went unnoticed, patch 2's aer_inject using ftrace hooks
> to pci config accessors is really cool and fixes several kernel crashes
> I encountered, but it may not work on every architecture. I'm not sure
> how widely aer_inject is used, so maybe there are no concerns with the
> DYNAMIC_FTRACE_WITH_REGS dependency, but I just want to reemphasize that
> dependency in case there are valid objections.

Oh, indeed, I hadn't noticed this arch dependency.  AFAICT, the new
DYNAMIC_FTRACE_WITH_REGS dependency means aer_inject will work only
on these arches:

  arm		# if (!XIP_KERNEL) && !CPU_ENDIAN_BE32 && MMU
  powerpc	# if PPC64 && CPU_LITTLE_ENDIAN
  riscv		# ARCH_RV64I only
  s390
  x86

Notably missing is arm64, which has DYNAMIC_FTRACE but not
DYNAMIC_FTRACE_WITH_REGS.

Bjorn