Re: [PATCH v6] irq: add quirk for broken interrupt remapping on 55XXchipsets
From: Don Dutile
Date: Mon Apr 08 2013 - 11:30:03 EST
On 04/05/2013 09:55 PM, Bjorn Helgaas wrote:
On Fri, Apr 5, 2013 at 1:31 PM, Neil Horman<nhorman@xxxxxxxxxxxxx> 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.
Bigger then that -- system reboots are often necessary, and for virtualization,
that means not just the lost of the device, but all guests running on that host.
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.
IRQ injection security bug *if* device-assignment of a PCI(e) device
to a KVM guest is done. To do so, requires kvm to be loaded with
a parameter to allow device-assignment w/o intr-remapping (b/c certain chipsets
didn't have intr-remap support complete until this past summer).
So, a sysadmin would have to consciously enable this security vulnerability,
and is only a vulnerability if (a) the guest is not well known/behaved or
(b) the assigned device goes-bonkers/breaks.
This vulnerability has been known and in existence since the beginning of
device-assignment; intr-remap is the way to isolate it.
The end result on this (rev of this) chip set is the equivalent of running
device-assignment on a (2009 era) Q35 chipset -- a VT-d1 (IOMMU-only,
no-intr-remap) capable chipset.
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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