[PATCH v3] irq: add quirk for broken interrupt remapping on 55XX chipsets

[Neil Horman]

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@xxxxxxxxxxxxx>
CC: Prarit Bhargava <prarit@xxxxxxxxxx>
CC: Don Zickus <dzickus@xxxxxxxxxx>
CC: Don Dutile <ddutile@xxxxxxxxxx>
CC: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
CC: Asit Mallick <asit.k.mallick@xxxxxxxxx>
CC: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
CC: linux-pci@xxxxxxxxxxxxxxx
---

Change notes:

v2)

* Moved the quirk to the x86 arch, since consensus seems to be that the 55XX
chipset series is x86 only.  I decided however to keep the quirk as a regular
quirk, not an early_quirk.  Early quirks have no way currently to determine if
BIOS has properly disabled the feature in the iommu, at least not without
significant hacking, and since its quite possible this will be a short lived
quirk, should Don Z's workaround code prove successful (and it looks like it may
well), I don't think that necessecary.

* Removed the WARNING banner from the quirk, and added the HW_ERR token to the
string, I opted to leave the newlines in place however, as I really couldnt
find a way to keep the text on a single line is still legible from a code
perspective.  I think theres enough language in there that using cscope on just
about any substring however will turn it up, and again, this may be a short
lived quirk.

v3)

* removed defines from pci_ids.h, and used direct id values as per request from
Bjorn.
---
 arch/x86/kernel/quirks.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/x86/kernel/quirks.c b/arch/x86/kernel/quirks.c
index 26ee48a..7c99675 100644
--- a/arch/x86/kernel/quirks.c
+++ b/arch/x86/kernel/quirks.c
@@ -5,6 +5,7 @@
 #include <linux/irq.h>
 
 #include <asm/hpet.h>
+#include "../../../drivers/iommu/irq_remapping.h"
 
 #if defined(CONFIG_X86_IO_APIC) && defined(CONFIG_SMP) && defined(CONFIG_PCI)
 
@@ -567,3 +568,20 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_NB_F5,
 			quirk_amd_nb_node);
 
 #endif
+
+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(HW_ERR "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, 0x3406, intel_remapping_check);
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x3403, intel_remapping_check);
-- 
1.8.1.4

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