diff options
Diffstat (limited to 'docs/interop/vhost-user.txt')
| -rw-r--r-- | docs/interop/vhost-user.txt | 33 |
1 files changed, 30 insertions, 3 deletions
diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt index fd8ac56562..d49444e037 100644 --- a/docs/interop/vhost-user.txt +++ b/docs/interop/vhost-user.txt @@ -66,11 +66,14 @@ Depending on the request type, payload can be: Index: a 32-bit vring index Flags: a 32-bit vring flags - Descriptor: a 64-bit user address of the vring descriptor table - Used: a 64-bit user address of the vring used ring - Available: a 64-bit user address of the vring available ring + Descriptor: a 64-bit ring address of the vring descriptor table + Used: a 64-bit ring address of the vring used ring + Available: a 64-bit ring address of the vring available ring Log: a 64-bit guest address for logging + Note that a ring address is an IOVA if VIRTIO_F_IOMMU_PLATFORM has been + negotiated. Otherwise it is a user address. + * Memory regions description --------------------------------------------------- | num regions | padding | region0 | ... | region7 | @@ -273,6 +276,30 @@ Once the source has finished migration, rings will be stopped by the source. No further update must be done before rings are restarted. +Memory access +------------- + +The master sends a list of vhost memory regions to the slave using the +VHOST_USER_SET_MEM_TABLE message. Each region has two base addresses: a guest +address and a user address. + +Messages contain guest addresses and/or user addresses to reference locations +within the shared memory. The mapping of these addresses works as follows. + +User addresses map to the vhost memory region containing that user address. + +When the VIRTIO_F_IOMMU_PLATFORM feature has not been negotiated: + + * Guest addresses map to the vhost memory region containing that guest + address. + +When the VIRTIO_F_IOMMU_PLATFORM feature has been negotiated: + + * Guest addresses are also called I/O virtual addresses (IOVAs). They are + translated to user addresses via the IOTLB. + + * The vhost memory region guest address is not used. + IOMMU support ------------- |