9 Mar
2023
9 Mar
'23
2:02 p.m.
On 2023/3/9 16:08, Yi Liu wrote:
Nested translation is a hardware feature that is supported by many modern IOMMU hardwares. It has two stages (stage-1, stage-2) address translation to get access to the physical address. stage-1 translation table is owned by userspace (e.g. by a guest OS), while stage-2 is owned by kernel. Changes to stage-1 translation table should be followed by an IOTLB invalidation.
The last sentence is not always true. If any entry of the stage-1 translation table is changed from non-present to present, the IOTLB has no chance to cache it yet. Hence there's no need for invalidation.
Best regards, baolu