[PATCH v7] 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.  For
details of those that reported the problem, please see:
https://bugzilla.redhat.com/show_bug.cgi?id=887006

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
CC: Joerg Roedel <joro@xxxxxxxxxx>
CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---

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.

v4)

* Converted pr_warn to WARN_TAINT(TAINT_FIRMWARE_WORKAROUND) as per David
Woodhouse

v5)

* Moved check to an early quirk, and flagged the broken chip, so we could
reasonably disable irq remapping during bootup.

v6)

* Clean up of stupid extra thrash in quirks.c

v7)

* Move broken check to intel_irq_remapping.c
* Fixed another typo
* Finally made the reference bugzilla public
---
 arch/x86/kernel/early-quirks.c      | 25 +++++++++++++++++++++++++
 drivers/iommu/intel_irq_remapping.c | 10 ++++++++++
 drivers/iommu/irq_remapping.c       | 12 ++++++++++++
 drivers/iommu/irq_remapping.h       |  1 +
 4 files changed, 48 insertions(+)

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/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
index f3b8f23..5b19b2d 100644
--- a/drivers/iommu/intel_irq_remapping.c
+++ b/drivers/iommu/intel_irq_remapping.c
@@ -524,6 +524,16 @@ static int __init intel_irq_remapping_supported(void)
 
 	if (disable_irq_remap)
 		return 0;
+	if (irq_remap_broken) {
+		WARN_TAINT(1, TAINT_FIRMWARE_WORKAROUND,
+			   "This system BIOS has enabled interrupt remapping\n"
+			   "on a chipset that contains an erratum making that\n"
+			   "feature unstable.  To maintain system stability\n"
+			   "interrupt remapping is being disabled.  Please\n"
+			   "contact your BIOS vendor for an update\n");
+		disable_irq_remap = 1;
+		return 0;
+	}
 
 	if (!dmar_ir_support())
 		return 0;
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 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");
+		disable_irq_remap = 1;
+		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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