[PATCH] iommu: always select INTEL_IOMMU for IRQ_REMAP

[Arnd Bergmann <arnd@kernel.org>]

From: Arnd Bergmann <arnd@arndb.de>

CONFIG_INTR_REMAP was originally split out of the intel iommu code to be
shared by IRQ_REMAP. This recently broke again because the IRQ_REMAP
code calls the global device_rbtree_find() function that is unavailable
for builds without INTEL_IOMMU:

x86_64-linux-ld: vmlinux.o: in function `qi_submit_sync':
(.text+0x10771e0): undefined reference to `device_rbtree_find'

It seems that the intel iommu code now contains a lot of generic helper
functions that are not specific to intel, such as alloc_pgtable_page(),
iommu_flush_write_buffer(), domain_attach_iommu() etc, so presumably
it is not x86 specific any more.

Fix the build failure for now by just selectin INTEL_IOMMU by the
code that relies on it. It might be helpful to split out all the
functions without an intel_iommu_* prefix into a helper library
to avoid including the x86 specific bits on non-x86, but that could
be a follow-up.

Fixes: d3f138106b4b ("iommu: Rename the DMAR and INTR_REMAP config options")
Fixes: 80a9b50c0b9e ("iommu/vt-d: Improve ITE fault handling if target device isn't present")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
Not sure about this one, I just ran across the build regression and
wasn't sure if the intel-iommu functions are meant to be generic
or just misnamed. The patch description assumes the former, if that
is wrong, it needs a different explanation or a different fix.
---
 drivers/iommu/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index df156f0a1a17..da5339bdb7e7 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -196,6 +196,7 @@ config IRQ_REMAP
 	bool "Support for Interrupt Remapping"
 	depends on X86_64 && X86_IO_APIC && PCI_MSI && ACPI
 	select DMAR_TABLE
+	select INTEL_IOMMU
 	help
 	  Supports Interrupt remapping for IO-APIC and MSI devices.
 	  To use x2apic mode in the CPU's which support x2APIC enhancements or
-- 
2.39.2