Patch "ACPI, PCI: Penalize legacy IRQ used by ACPI SCI" has been added to the 4.2-stable tree

This is a note to let you know that I've just added the patch titled

ACPI, PCI: Penalize legacy IRQ used by ACPI SCI

to the 4.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
acpi-pci-penalize-legacy-irq-used-by-acpi-sci.patch
and it can be found in the queue-4.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Jiang Liu <[email protected]>
Date: Fri, 21 Aug 2015 15:36:23 +0800
Subject: ACPI, PCI: Penalize legacy IRQ used by ACPI SCI

From: Jiang Liu <[email protected]>

commit 5d0ddfebb93069061880fc57ee4ba7246bd1e1ee upstream.

Nick Meier reported a regression with HyperV that "
After rebooting the VM, the following messages are logged in syslog when trying to load the tulip driver:

    tulip: Linux Tulip drivers version 1.1.15 (Feb 27, 2007)
    tulip: 0000:00:0a.0: PCI INT A: failed to register GSI
    tulip: Cannot enable tulip board #0, aborting
    tulip: probe of 0000:00:0a.0 failed with error -16

Errors occur in 3.19.0 kernel
Works in 3.17 kernel.
"

According to the ACPI dump file posted by Nick at
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1440072

The ACPI MADT table includes an interrupt source overridden entry for ACPI SCI:

[236h 0566  1]                Subtable Type : 02 <Interrupt Source Override>
[237h 0567  1]                       Length : 0A
[238h 0568  1]                          Bus : 00
[239h 0569  1]                       Source : 09
[23Ah 0570  4]                    Interrupt : 00000009
[23Eh 0574  2]        Flags (decoded below) : 000D

Polarity : 1
Trigger Mode : 3

And in DSDT table, we have _PRT method to define PCI interrupts, which eventually goes to:

        Name (PRSA, ResourceTemplate ()
        {
            IRQ (Level, ActiveLow, Shared, )
                {3,4,5,7,9,10,11,12,14,15}
        })
        Name (PRSB, ResourceTemplate ()
        {
            IRQ (Level, ActiveLow, Shared, )
                {3,4,5,7,9,10,11,12,14,15}
        })
        Name (PRSC, ResourceTemplate ()
        {
            IRQ (Level, ActiveLow, Shared, )
                {3,4,5,7,9,10,11,12,14,15}
        })
        Name (PRSD, ResourceTemplate ()
        {
            IRQ (Level, ActiveLow, Shared, )
                {3,4,5,7,9,10,11,12,14,15}
        })

According to the MADT and DSDT tables, IRQ 9 may be used for:
1) ACPI SCI in level, high mode
2) PCI legacy IRQ in level, low mode
So there's a conflict in polarity setting for IRQ 9.

Prior to commit cd68f6bd53cf ("x86, irq, acpi: Get rid of special handling of GSI for ACPI SCI"), ACPI SCI is handled specially and there's no check for conflicts between ACPI SCI and PCI legagy IRQ. And it seems that the HyperV hypervisor doesn't make use of the polarity configuration in IOAPIC entry, so it just works.

Commit cd68f6bd53cf gets rid of the specially handling of ACPI SCI, and then the pin attribute checking code discloses the conflicts between ACPI SCI and PCI legacy IRQ on HyperV virtual machine, and rejects the request to assign IRQ9 to PCI devices.

So penalize legacy IRQ used by ACPI SCI and mark it unusable if ACPI SCI attributes conflict with PCI IRQ attributes.

Please refer to following links for more information:
https://bugzilla.kernel.org/show_bug.cgi?id=101301
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1440072

---
 arch/x86/kernel/acpi/boot.c |    1 +
 drivers/acpi/pci_link.c     |   16 ++++++++++++++++
 include/linux/acpi.h        |    2 +-
 3 files changed, 18 insertions(+), 1 deletion(-)

@@ -445,6 +445,7 @@ static void __init acpi_sci_ioapic_setup
 		polarity = acpi_sci_flags & ACPI_MADT_POLARITY_MASK;
 
 	mp_override_legacy_irq(bus_irq, polarity, trigger, gsi);
+	acpi_penalize_sci_irq(bus_irq, trigger, polarity);
 
 	/*
 	 * stash over-ride to indicate we've been here

@@ -826,6 +826,22 @@ void acpi_penalize_isa_irq(int irq, int
 }
 
 /*
+ * Penalize IRQ used by ACPI SCI. If ACPI SCI pin attributes conflict with
+ * PCI IRQ attributes, mark ACPI SCI as ISA_ALWAYS so it won't be use for
+ * PCI IRQs.
+ */
+void acpi_penalize_sci_irq(int irq, int trigger, int polarity)
+{
+	if (irq >= 0 && irq < ARRAY_SIZE(acpi_irq_penalty)) {
+		if (trigger != ACPI_MADT_TRIGGER_LEVEL ||
+		    polarity != ACPI_MADT_POLARITY_ACTIVE_LOW)
+			acpi_irq_penalty[irq] += PIRQ_PENALTY_ISA_ALWAYS;
+		else
+			acpi_irq_penalty[irq] += PIRQ_PENALTY_PCI_USING;
+	}
+}
+
+/*
  * Over-ride default table to reserve additional IRQs for use by ISA
  * e.g. acpi_irq_isa=5
  * Useful for telling ACPI how not to interfere with your ISA sound card.

@@ -221,7 +221,7 @@ struct pci_dev;
 
 int acpi_pci_irq_enable (struct pci_dev *dev);
 void acpi_penalize_isa_irq(int irq, int active);
-
+void acpi_penalize_sci_irq(int irq, int trigger, int polarity);
 void acpi_pci_irq_disable (struct pci_dev *dev);
 
 extern int ec_read(u8 addr, u8 *val);

Patches currently in stable-queue which might be from [email protected] are

queue-4.2/acpi-pci-penalize-legacy-irq-used-by-acpi-sci.patch