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Message-ID: <CAErSpo6z8oqiaUBCieUMsS_c5xvVFUDbHqVO_eBBde3uv2=zcg@mail.gmail.com>
Date: Fri, 5 Apr 2013 19:55:51 -0600
From: Bjorn Helgaas <bhelgaas@...gle.com>
To: Neil Horman <nhorman@...driver.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Prarit Bhargava <prarit@...hat.com>,
Don Zickus <dzickus@...hat.com>,
Don Dutile <ddutile@...hat.com>,
Asit Mallick <asit.k.mallick@...el.com>,
David Woodhouse <dwmw2@...radead.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH v6] irq: add quirk for broken interrupt remapping on 55XX chipsets
On Fri, Apr 5, 2013 at 1:31 PM, 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.
I'd still like to mention the bugzilla URL in the changelog
(https://bugzilla.redhat.com/show_bug.cgi?id=887006) if it can be made
public.
> ...
> diff --git a/arch/x86/kernel/early-quirks.c b/arch/x86/kernel/early-quirks.c
> index 3755ef4..bfa3139 100644
> --- a/arch/x86/kernel/early-quirks.c
> +++ b/arch/x86/kernel/early-quirks.c
> @@ -192,6 +192,27 @@ static void __init ati_bugs_contd(int num, int slot, int func)
> }
> #endif
>
> +#ifdef CONFIG_IRQ_REMAP
> +static void __init intel_remapping_check(int num, int slot, int func)
> +{
> + u8 revision;
> +
> + revision = pci_read_config_byte(num, slot, func , PCI_REVISION_ID);
> +
> + /*
> + * Revision 0x13 of this chipset supports irq remapping
> + * but has an erratum that breaks its behavior, flag it as such
> + */
> + if (revision == 0x13)
> + irq_remap_broken = 1;
> +
> +}
> +#else
> +static void __init intel_remapping_check(int num, int slot, int func)
> +{
> +}
> +#endif
> +
> #define QFLAG_APPLY_ONCE 0x1
> #define QFLAG_APPLIED 0x2
> #define QFLAG_DONE (QFLAG_APPLY_ONCE|QFLAG_APPLIED)
> @@ -221,6 +242,10 @@ static struct chipset early_qrk[] __initdata = {
> PCI_CLASS_SERIAL_SMBUS, PCI_ANY_ID, 0, ati_bugs },
> { PCI_VENDOR_ID_ATI, PCI_DEVICE_ID_ATI_SBX00_SMBUS,
> PCI_CLASS_SERIAL_SMBUS, PCI_ANY_ID, 0, ati_bugs_contd },
> + { PCI_VENDOR_ID_INTEL, 0x3403, PCI_CLASS_BRIDGE_HOST,
> + PCI_BASE_CLASS_BRIDGE, 0, intel_remapping_check },
> + { PCI_VENDOR_ID_INTEL, 0x3406, PCI_CLASS_BRIDGE_HOST,
> + PCI_BASE_CLASS_BRIDGE, 0, intel_remapping_check },
> {}
> };
>
> diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c
> index d56f8c1..2b56e92 100644
> --- a/drivers/iommu/irq_remapping.c
> +++ b/drivers/iommu/irq_remapping.c
> @@ -19,6 +19,7 @@
> int irq_remapping_enabled;
>
> int disable_irq_remap;
> +int irq_remap_broken;
> int disable_sourceid_checking;
> int no_x2apic_optout;
>
> @@ -216,6 +217,17 @@ int irq_remapping_supported(void)
> if (disable_irq_remap)
> return 0;
>
> + if (irq_remap_broken) {
> + WARN_TAINT(1, TAIN_FIRMWARE_WORKAROUND,
This looks like a typo (s/TAIN/TAINT/).
> + "This system BIOS has enabled interrupt remapping\n"
> + "on a chipset that contains an erratum 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");
I suspect your updated message won't mention "nointremap", but if it
does, Documentation/kernel-parameters.txt says that option is
deprecated and "intremap=off" should be used instead.
> + disable_irq_remap = 1;
Tell me if I have this correct:
Before this patch, we had interrupt remapping enabled and
virtualization enabled. This is safe, but devices might need resets
to deal with lost or spurious interrupts.
After this patch, these same machines will by default have interrupt
remapping disabled and virtualization enabled. The lost or spurious
interrupt problem should be gone, but we now have the IRQ injection
security bug.
If that's really the change we're making, I'm not comfortable applying
this patch. But I don't know the details of the IRQ injection
problem, so maybe my understanding of the implications is wrong.
> + return 0;
> + }
> +
> if (!remap_ops || !remap_ops->supported)
> return 0;
>
> diff --git a/drivers/iommu/irq_remapping.h b/drivers/iommu/irq_remapping.h
> index ecb6376..d7537e4 100644
> --- a/drivers/iommu/irq_remapping.h
> +++ b/drivers/iommu/irq_remapping.h
> @@ -32,6 +32,7 @@ struct pci_dev;
> struct msi_msg;
>
> extern int disable_irq_remap;
> +extern int irq_remap_broken;
> extern int disable_sourceid_checking;
> extern int no_x2apic_optout;
> extern int irq_remapping_enabled;
> --
> 1.8.1.4
>
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