KVM: Enable snooping control for supported hardware

Memory aliases with different memory type is a problem for guest. For the guest
without assigned device, the memory type of guest memory would always been the
same as host(WB); but for the assigned device, some part of memory may be used
as DMA and then set to uncacheable memory type(UC/WC), which would be a conflict of
host memory type then be a potential issue.

Snooping control can guarantee the cache correctness of memory go through the
DMA engine of VT-d.

[avi: fix build on ia64]

Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 72d56844f388..bdce8e1303c9 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -367,6 +367,9 @@ void kvm_unregister_irq_ack_notifier(struct kvm_irq_ack_notifier *kian);
 int kvm_request_irq_source_id(struct kvm *kvm);
 void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id);
 
+/* For vcpu->arch.iommu_flags */
+#define KVM_IOMMU_CACHE_COHERENCY       0x1
+
 #ifdef CONFIG_IOMMU_API
 int kvm_iommu_map_pages(struct kvm *kvm, gfn_t base_gfn,
                         unsigned long npages);