intel_iommu: support snoop control
SC is required for some kernel features like vhost-vDPA. So this patch
implements basic SC feature. The idea is pretty simple, for software
emulated DMA it would be always coherent. In this case we can simple
advertise ECAP_SC bit. For VFIO and vhost, thing will be more much
complicated, so this patch simply fail the IOMMU notifier
registration.
In the future, we may want to have a dedicated notifiers flag or
similar mechanism to demonstrate the coherency so VFIO could advertise
that if it has VFIO_DMA_CC_IOMMU, for vhost kernel backend we don't
need that since it's a software backend.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220214060346.72455-1-jasowang@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
index a6c7880..1ff13b4 100644
--- a/hw/i386/intel_iommu_internal.h
+++ b/hw/i386/intel_iommu_internal.h
@@ -188,6 +188,7 @@
#define VTD_ECAP_IR (1ULL << 3)
#define VTD_ECAP_EIM (1ULL << 4)
#define VTD_ECAP_PT (1ULL << 6)
+#define VTD_ECAP_SC (1ULL << 7)
#define VTD_ECAP_MHMV (15ULL << 20)
#define VTD_ECAP_SRS (1ULL << 31)
#define VTD_ECAP_SMTS (1ULL << 43)
