linux-kernel - Re: [PATCH] irq: add quirk for broken interrupt remapping on 55XX chipsets

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Date:	Fri, 1 Mar 2013 14:29:58 -0500
From:	Neil Horman <nhorman@...driver.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Prarit Bhargava <prarit@...hat.com>,
	Don Zickus <dzickus@...hat.com>,
	Don Dutile <ddutile@...hat.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Asit Mallick <asit.k.mallick@...el.com>,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH] irq: add quirk for broken interrupt remapping on 55XX
 chipsets

On Fri, Mar 01, 2013 at 10:20:35AM -0800, Yinghai Lu wrote:
> On Fri, Mar 1, 2013 at 9:17 AM, Neil Horman <nhorman@...driver.com> wrote:
> > A few years back intel published a spec update:
> > http://www.intel.com/content/dam/doc/specification-update/5520-and-5500-chipset-ioh-specification-update.pdf
> >
> > For the 5520 and 5500 chipsets which contained an errata (specificially errata
> > 53), which noted that these chipsets can't properly do interrupt remapping, and
> > as a result the recommend that interrupt remapping be disabled in bios.  While
> > many vendors have a bios update to do exactly that, not all do, and of course
> > not all users update their bios to a level that corrects the problem.  As a
> > result, occasionally interrupts can arrive at a cpu even after affinity for that
> > interrupt has be moved, leading to lost or spurrious interrupts (usually
> > characterized by the message:
> > kernel: do_IRQ: 7.71 No irq handler for vector (irq -1)
> >
> > There have been several incidents recently of people seeing this error, and
> > investigation has shown that they have system for which their BIOS level is such
> > that this feature was not properly turned off.  As such, it would be good to
> > give them a reminder that their systems are vulnurable to this problem.
> >
> > Signed-off-by: Neil Horman <nhorman@...driver.com>
> > CC: Prarit Bhargava <prarit@...hat.com>
> > CC: Don Zickus <dzickus@...hat.com>
> > CC: Don Dutile <ddutile@...hat.com>
> > CC: Bjorn Helgaas <bhelgaas@...gle.com>
> > CC: Asit Mallick <asit.k.mallick@...el.com>
> > CC: linux-pci@...r.kernel.org
> > ---
> >  drivers/iommu/intel_irq_remapping.c | 20 ++++++++++++++++++++
> >  include/linux/pci_ids.h             |  2 ++
> >  2 files changed, 22 insertions(+)
> >
> > diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
> > index f3b8f23..9bfb6c2 100644
> > --- a/drivers/iommu/intel_irq_remapping.c
> > +++ b/drivers/iommu/intel_irq_remapping.c
> > @@ -1113,3 +1113,23 @@ struct irq_remap_ops intel_irq_remap_ops = {
> >         .msi_setup_irq          = intel_msi_setup_irq,
> >         .setup_hpet_msi         = intel_setup_hpet_msi,
> >  };
> > +
> > +
> > +static void intel_remapping_check(struct pci_dev *dev)
> > +{
> > +       u8 revision;
> > +
> > +       pci_read_config_byte(dev, PCI_REVISION_ID, &revision);
> > +
> > +       if ((revision == 0x13) && irq_remapping_enabled) {
> > +               pr_warn("WARNING WARNING WARNING WARNING WARNING WARNING\n"
> > +                       "This system BIOS has enabled interrupt remapping\n"
> > +                       "on a chipset that contains an errata making that\n"
> > +                       "feature unstable.  Please reboot with nointremap\n"
> > +                       "added to the kernel command line and contact\n"
> > +                       "your BIOS vendor for an update");
> > +       }
> > +}
> > +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_5520_IOHUB, intel_remapping_check);
> > +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_5500_IOHUB, intel_remapping_check);
> 
> only for x86 platform?
> If so, you can check that in arch/x86/kernel/early-quirks.c::early_quirks()
> and set one flag and later print warning and skip there if someone
> need to enable intr-remap.
> So users will not need to reboot the system...
> 
> Thanks
> 
I was under the impression that BIOS might have enabled irq remapping prior to
the OS booting, at which point a reboot was requried anyway.

Neil

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