[PATCH] x86: fix PCI_MSI build on !SMP

[Thomas Petazzoni]

Commit ebd97be635 ('PCI: remove ARCH_SUPPORTS_MSI kconfig option')
removed the ARCH_SUPPORTS_MSI option which architectures could select
to indicate that they support MSI. Now, all architectures are supposed
to build fine when MSI support is enabled: instead of having the
architecture tell *when* MSI support can be used, it's up to the
architecture code to ensure that MSI support can be enabled.

On x86, commit ebd97be635 removed the following line:

  select ARCH_SUPPORTS_MSI if (X86_LOCAL_APIC && X86_IO_APIC)

Which meant that MSI support was only available when the local APIC
and I/O APIC were enabled. While this is always true on SMP or x86-64,
it is not necessarily the case on i386 !SMP.

The below patch makes sure that the local APIC and I/O APIC support is
always enabled when MSI support is enabled. To do so, it:

 * Ensures the X86_UP_APIC option is not visible when PCI_MSI is
   enabled. This is the option that allows, on UP machines, to enable
   or not the APIC support. It is already not visible on SMP systems,
   or x86-64 systems, for example. We're simply also making it
   invisible on i386 MSI systems.

 * Ensures that the X86_LOCAL_APIC and X86_IO_APIC options are 'y'
   when PCI_MSI is enabled.

Notice that this change requires a change in drivers/iommu/Kconfig to
avoid a recursive Kconfig dependencey. The AMD_IOMMU option selects
PCI_MSI, but was depending on X86_IO_APIC. This dependency is no
longer needed: as soon as PCI_MSI is selected, the presence of
X86_IO_APIC is guaranteed. Moreover, the AMD_IOMMU already depended on
X86_64, which already guaranteed that X86_IO_APIC was enabled, so this
dependency was anyway redundant.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx>
Reported-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: bhelgaas@xxxxxxxxxx
Cc: benh@xxxxxxxxxxxxxxxxxxx
Cc: daniel.price@xxxxxxxxx
Cc: thierry.reding@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: jason@xxxxxxxxxxxxxx
Cc: x86@xxxxxxxxxx
---
As this patch fixes a regression introduced by ebd97be635, which got
merged in 3.12-rc1, this patch should be applied as part of the
3.12-rc cycle.
---
 arch/x86/Kconfig      | 6 +++---
 drivers/iommu/Kconfig | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ee2fb9d..145d703 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -860,7 +860,7 @@ source "kernel/Kconfig.preempt"
 
 config X86_UP_APIC
 	bool "Local APIC support on uniprocessors"
-	depends on X86_32 && !SMP && !X86_32_NON_STANDARD
+	depends on X86_32 && !SMP && !X86_32_NON_STANDARD && !PCI_MSI
 	---help---
 	  A local APIC (Advanced Programmable Interrupt Controller) is an
 	  integrated interrupt controller in the CPU. If you have a single-CPU
@@ -885,11 +885,11 @@ config X86_UP_IOAPIC
 
 config X86_LOCAL_APIC
 	def_bool y
-	depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC
+	depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_APIC || PCI_MSI
 
 config X86_IO_APIC
 	def_bool y
-	depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_IOAPIC
+	depends on X86_64 || SMP || X86_32_NON_STANDARD || X86_UP_IOAPIC || PCI_MSI
 
 config X86_VISWS_APIC
 	def_bool y
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index fe302e3..c880eba 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -52,7 +52,7 @@ config AMD_IOMMU
 	select PCI_PRI
 	select PCI_PASID
 	select IOMMU_API
-	depends on X86_64 && PCI && ACPI && X86_IO_APIC
+	depends on X86_64 && PCI && ACPI
 	---help---
 	  With this option you can enable support for AMD IOMMU hardware in
 	  your system. An IOMMU is a hardware component which provides
-- 
1.8.1.2

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