x86/iommu: make AMD-Vi and Intel VT-d support configurable

Provide the user with configuration control over the IOMMU support by making
AMD_IOMMU and INTEL_IOMMU options user selectable and able to be turned off.

However, there are cases where the IOMMU support is required, for instance for
a system with more than 254 CPUs. In order to prevent users from unknowingly
disabling it and ending up with a broken hypervisor, make the support user
selectable only if EXPERT is enabled.

To preserve the current default configuration of an x86 system, both options
depend on X86 and default to Y.

Signed-off-by: Xenia Ragiadakou <burzalodowa@gmail.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/drivers/passthrough/Kconfig b/xen/drivers/passthrough/Kconfig
index 5c6556774423bf2e486cc1aefbf54315e71037c2..864fcf3b0cef198dbfbd16496cfe8b1113feb03c 100644 (file)
--- a/xen/drivers/passthrough/Kconfig
+++ b/xen/drivers/passthrough/Kconfig
@@ -38,10 +38,28 @@ config IPMMU_VMSA
 endif
 
 config AMD_IOMMU
-       def_bool y if X86
+       bool "AMD IOMMU" if EXPERT
+       depends on X86
+       default y
+       help
+         Enables I/O virtualization on platforms that implement the
+         AMD I/O Virtualization Technology (IOMMU).
+
+         If your system includes an IOMMU implementing AMD-Vi, say Y.
+         This is required if your system has more than 254 CPUs.
+         If in doubt, say Y.
 
 config INTEL_IOMMU
-       def_bool y if X86
+       bool "Intel VT-d" if EXPERT
+       depends on X86
+       default y
+       help
+         Enables I/O virtualization on platforms that implement the
+         Intel Virtualization Technology for Directed I/O (Intel VT-d).
+
+         If your system includes an IOMMU implementing Intel VT-d, say Y.
+         This is required if your system has more than 254 CPUs.
+         If in doubt, say Y.
 
 config IOMMU_FORCE_PT_SHARE
        bool