diff options
Diffstat (limited to 'include/exec/memory.h')
| -rw-r--r-- | include/exec/memory.h | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/include/exec/memory.h b/include/exec/memory.h index c37ffdbcd1..2e602a2fad 100644 --- a/include/exec/memory.h +++ b/include/exec/memory.h @@ -129,6 +129,32 @@ struct IOMMUTLBEntry { /* * Bitmap for different IOMMUNotifier capabilities. Each notifier can * register with one or multiple IOMMU Notifier capability bit(s). + * + * Normally there're two use cases for the notifiers: + * + * (1) When the device needs accurate synchronizations of the vIOMMU page + * tables, it needs to register with both MAP|UNMAP notifies (which + * is defined as IOMMU_NOTIFIER_IOTLB_EVENTS below). + * + * Regarding to accurate synchronization, it's when the notified + * device maintains a shadow page table and must be notified on each + * guest MAP (page table entry creation) and UNMAP (invalidation) + * events (e.g. VFIO). Both notifications must be accurate so that + * the shadow page table is fully in sync with the guest view. + * + * (2) When the device doesn't need accurate synchronizations of the + * vIOMMU page tables, it needs to register only with UNMAP or + * DEVIOTLB_UNMAP notifies. + * + * It's when the device maintains a cache of IOMMU translations + * (IOTLB) and is able to fill that cache by requesting translations + * from the vIOMMU through a protocol similar to ATS (Address + * Translation Service). + * + * Note that in this mode the vIOMMU will not maintain a shadowed + * page table for the address space, and the UNMAP messages can cover + * more than the pages that used to get mapped. The IOMMU notifiee + * should be able to take care of over-sized invalidations. */ typedef enum { IOMMU_NOTIFIER_NONE = 0, |