kvm: Allow build-time configuration of KVM device assignment

We hope to at some point deprecate KVM legacy device assignment in
favor of VFIO-based assignment.  Towards that end, allow legacy
device assignment to be deconfigured.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

3 files changed, 18 insertions, 6 deletions

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 9d50efdb719d..a47a3e54b964 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -21,8 +21,6 @@ config KVM
         tristate "Kernel-based Virtual Machine (KVM) support"
         depends on HAVE_KVM
         depends on HIGH_RES_TIMERS
-        # for device assignment:
-        depends on PCI
         # for TASKSTATS/TASK_DELAY_ACCT:
         depends on NET
         select PREEMPT_NOTIFIERS
@@ -83,6 +81,17 @@ config KVM_MMU_AUDIT
          This option adds a R/W kVM module parameter 'mmu_audit', which allows
          audit  KVM MMU at runtime.
 
+config KVM_DEVICE_ASSIGNMENT
+        bool "KVM legacy PCI device assignment support"
+        depends on KVM && PCI && IOMMU_API
+        default y
+        ---help---
+          Provide support for legacy PCI device assignment through KVM.  The
+          kernel now also supports a full featured userspace device driver
+          framework through VFIO, which supersedes much of this support.
+
+          If unsure, say Y.
+
 # OK, it's a little counter-intuitive to do this, but it puts it neatly under
 # the virtualization menu.
 source drivers/vhost/Kconfig
diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index a797b8e43ade..d609e1d84048 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -7,8 +7,9 @@ CFLAGS_vmx.o := -I.
 
 kvm-y                   += $(addprefix ../../../virt/kvm/, kvm_main.o ioapic.o \
                                 coalesced_mmio.o irq_comm.o eventfd.o \
-                                assigned-dev.o irqchip.o)
-kvm-$(CONFIG_IOMMU_API) += $(addprefix ../../../virt/kvm/, iommu.o)
+                                irqchip.o)
+kvm-$(CONFIG_KVM_DEVICE_ASSIGNMENT)     += $(addprefix ../../../virt/kvm/, \
+                                assigned-dev.o iommu.o)
 kvm-$(CONFIG_KVM_ASYNC_PF)      += $(addprefix ../../../virt/kvm/, async_pf.o)
 
 kvm-y                   += x86.o mmu.o emulate.o i8259.o irq.o lapic.o \
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 145b1c81011b..8747fef7fd59 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2501,7 +2501,6 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_USER_NMI:
         case KVM_CAP_REINJECT_CONTROL:
         case KVM_CAP_IRQ_INJECT_STATUS:
-        case KVM_CAP_ASSIGN_DEV_IRQ:
         case KVM_CAP_IRQFD:
         case KVM_CAP_IOEVENTFD:
         case KVM_CAP_PIT2:
@@ -2519,9 +2518,12 @@ int kvm_dev_ioctl_check_extension(long ext)
         case KVM_CAP_XSAVE:
         case KVM_CAP_ASYNC_PF:
         case KVM_CAP_GET_TSC_KHZ:
-        case KVM_CAP_PCI_2_3:
         case KVM_CAP_KVMCLOCK_CTRL:
         case KVM_CAP_READONLY_MEM:
+#ifdef CONFIG_KVM_DEVICE_ASSIGNMENT
+        case KVM_CAP_ASSIGN_DEV_IRQ:
+        case KVM_CAP_PCI_2_3:
+#endif
                 r = 1;
                 break;
         case KVM_CAP_COALESCED_MMIO: