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By The Linux Camp News, October 21, 2026
Dynamic PAMT replaces an upfront TDX metadata reservation with incremental allocation, reducing overhead on lightly used confidential-VM hosts. The merge establishes development-tree support, not distribution availability.
Dynamic PAMT support entered the Linux 7.4 development tree, with the kernel pull-request tracker confirming the merge on October 20, 2026. The change targets memory overhead on Intel Trust Domain Extensions (TDX) hosts running confidential virtual machines. Dave Hansen submitted it for 7.4-rc1 on October 19; this is development-tree inclusion, not a final Linux 7.4 release. 3 1
Previously, enabling TDX meant committing roughly 0.4% of physical memory to metadata, according to Hansen's pull request, even with little TDX activity. PAMT, the Physical Address Metadata Table, holds that memory metadata. Dynamic PAMT lets it grow as needed, allocating metadata covering 2 MB of host memory at a time. That figure describes the memory covered, not a 2 MB metadata allocation. The result is less upfront reservation rather than elimination of metadata. 2 1
The integration reaches into KVM's management of TDX memory. The patch list includes PAMT allocation for trust-domain and virtual-CPU control structures, plus PAMT page get/put operations when private memory is mapped or unmapped. This connects metadata handling to the resources and mappings being managed, rather than treating it solely as a host-wide reservation. 2
The useful capacity-planning distinction is TDX utilization. Hansen identifies low-utilization hosts as the beneficiaries: less DRAM must be committed to metadata when little TDX memory is needed. This is not a general RAM reduction for every Intel server or ordinary VM workload, nor does the approximate 0.4% baseline establish a fixed saving at every utilization level. 2
For deployment planning, treat the merge as kernel support for a TDX module feature, not proof that a particular host can use it. The pull request retrieved on October 21, 2026 does not identify compatible module versions, activation requirements or measured savings. Those remain checks to resolve before budgeting reclaimed RAM; the maintainer's explanation establishes the allocation model, not a benchmark or platform compatibility matrix. 2