[Patch v2] x86, ACPI, irq: Add a quirk to override SCI polarity for HyperV

[Jiang Liu <jiang.liu@linux.intel.com>]

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 above, 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 possible 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 logic discloses the conflicts
between ACPI SCI and PCI legacy IRQ on HyperV virtual machine,
and rejects the request to assign IRQ9 to PCI devices.

Since HyperV doesn't make use of the IOAPIC polarity setting,
add a quirk to enforce ACPI SCI as level, low on HyperV guests,
so IRQ9 could be used for both ACPI SCI and PCI legacy IRQ.

Nick reports the proposed patch fixes the regression as "
  Applied the above proposed patch with the DMI values substituted.
  The tulip driver loaded, and an address was assigned via DHCP.
"
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

Fixes: cd68f6bd53cf ("x86, irq, acpi: Get rid of special handling of GSI for ACPI SCI")
Reported-and-tested-by: Nick Meier <nmeier@microsoft.com>
Cc: <stable@vger.kernel.org> # 3.19
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
---
Hi Thomas,
	I have refined the commit message to explain why it works with
the old code.
Thanks!
Gerry
---
 arch/x86/kernel/acpi/boot.c |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index e49ee24da85e..47d95a86d56d 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -1308,6 +1308,13 @@ static int __init dmi_ignore_irq0_timer_override(const struct dmi_system_id *d)
 	return 0;
 }
 
+static int __init acpi_force_hyperv_sci_attr(const struct dmi_system_id *d)
+{
+	acpi_sci_flags = ACPI_MADT_POLARITY_ACTIVE_LOW |
+		(acpi_sci_flags & ~ACPI_MADT_POLARITY_MASK);
+	return 0;
+}
+
 /*
  * ACPI offers an alternative platform interface model that removes
  * ACPI hardware requirements for platforms that do not implement
@@ -1458,6 +1465,14 @@ static struct dmi_system_id __initdata acpi_dmi_table_late[] = {
 		     DMI_MATCH(DMI_PRODUCT_NAME, "AMILO PRO V2030"),
 		     },
 	 },
+	{
+	 .callback = acpi_force_hyperv_sci_attr,
+	 .ident = "HyperV",
+	 .matches = {
+		     DMI_MATCH(DMI_SYS_VENDOR, "Microsoft Corporation"),
+		     DMI_MATCH(DMI_PRODUCT_NAME, "Virtual Machine"),
+		     },
+	 },
 	{}
 };
 
-- 
1.7.10.4