# Linux 7.4 merges Dynamic PAMT to cut Intel TDX memory overhead

> **Key takeaway:** Dynamic PAMT replaces a fixed 0.4% RAM reservation for TDX metadata with on-demand 2 MB allocations, reducing memory waste on lightly loaded Intel Xeon servers.

**Published:** 2026-10-21T00:26:59+00:00 
**Source:** Phoronix Benchmarks & Drivers 
**Category:** kernel-os 
**Canonical URL:** https://fosswire.org/news/linux-74-merges-dynamic-pamt-to-cut-intel-tdx-memory-overhea.html 

## Summary
Intel's Dynamic PAMT feature has been merged for Linux 7.4, targeting servers running Intel Trust Domain Extensions (TDX). Previously, TDX required reserving roughly 0.4% of total system RAM upfront for Physical Address Metadata Table (PAMT) structures regardless of actual VM load. The new implementation allocates metadata in 2 MB chunks as needed. The same TDX module update also adds quote buffer size enumeration to accommodate larger post-quantum cryptography attestation quotes.

## How Dynamic PAMT changes TDX memory allocation
- **Before**: TDX host systems statically reserved ~0.4% of physical memory for PAMT metadata; this was all-or-nothing
- **After**: Dynamic PAMT allocates metadata in 2 MB increments of host memory as TDX VMs are created
- **Benefit**: Unused metadata memory remains available to the host when TDX utilization is low
- **Secondary change**: TDX module now enumerates quote buffer sizes, replacing fixed 128 KB buffers too small for post-quantum cryptography
- **Scope**: Affects Intel Xeon servers with TDX enabled; no change for non-TDX workloads

## Why it matters
For data centers running Intel TDX, this removes a significant memory tax on hosts that are not fully saturated with confidential VMs. Given current DRAM pricing and supply constraints, reclaiming hundreds of gigabytes on large-memory Xeon systems is operationally meaningful.