On Sat, May 12, 2018 at 06:25:13PM +0530, valmiki wrote:
> Hi All,
>
> What is the difference between IOVA address and bus address
> when SMMU is enabled ?
>
> Is IOVA address term used only when hypervisor is present ?
IOVA = IO virtual address. IOVA is the term normally used to describe
the address used on the _device_ side of an IOMMU.
For any general setup:
RAM ----- MMU ----- DEVICE
^ ^
physical virtual
address address
where "device" can be an IO device or a CPU, the terms still apply.
If you have something like this:
RAM ----- PCI bridge ----- MMU ----- DEVICE
^ ^ ^
physical bus virtual
address address address
You could also have (eg, in the case of a system MMU):
RAM ----- MMU ----- PCI bridge ----- DEVICE
^ ^ ^
physical virtual bus
address address address
(this can also be
considered a bus
address!)
In both of the above two cases, the PCI bridge may perform some address
translation, meaning that the bus address is different from the address
seen on the other side of the bridge.
So, the terms used depend exactly on the overall bus topology.
In the case of a system MMU, where the system MMU sits between peripheral
devices and RAM, then the bus addresses are the same as the
_IOVA of the system MMU_.
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