On 6/25/2020 12:25 AM, Alex Williamson wrote:
On Sun, 21 Jun 2020 01:51:22 +0530
Kirti Wankhede <kwankh...@nvidia.com> wrote:
Create mapped iova list when vIOMMU is enabled. For each mapped iova
save translated address. Add node to list on MAP and remove node from
list on UNMAP.
This list is used to track dirty pages during migration.
This seems like a lot of overhead to support that the VM might migrate.
Is there no way we can build this when we start migration, for example
replaying the mappings at that time? Thanks,
In my previous version I tried to go through whole range and find valid
iotlb, as below:
+ if (memory_region_is_iommu(section->mr)) {
+ iotlb = address_space_get_iotlb_entry(container->space->as,
iova,
+ true,
MEMTXATTRS_UNSPECIFIED);
When mapping doesn't exist, qemu throws error as below:
qemu-system-x86_64: vtd_iova_to_slpte: detected slpte permission error
(iova=0x0, level=0x3, slpte=0x0, write=1)
qemu-system-x86_64: vtd_iommu_translate: detected translation failure
(dev=00:03:00, iova=0x0)
qemu-system-x86_64: New fault is not recorded due to compression of faults
Secondly, it iterates through whole range with IOMMU page size
granularity which is 4K, so it takes long time resulting in large
downtime. With this optimization, downtime with vIOMMU reduced
significantly.
Other option I will try if I can check that if migration is supported
then only create this list.
Thanks,
Kirti
