From 1e0eba60af85cde427eec65be699769fb2222d55 Mon Sep 17 00:00:00 2001
From: Champ-Goblem <cameron@northflank.com>
Date: Fri, 6 Feb 2026 17:13:07 +0000
Subject: [PATCH] vmm: always try THP for VM RAM

The kernel allows madvise on shared memory if
/sys/kernel/mm/transparent_hugepage/shmem_enabled is set.
Always try and configure THP via madvise when
the user requests THP be enabled.
If this fails, only a warning log is emitted and THP won't be enabled.

Signed-off-by: Champ-Goblem <cameron@northflank.com>
---
 vmm/src/memory_manager.rs | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/vmm/src/memory_manager.rs b/vmm/src/memory_manager.rs
index 2011e4768..03b7b8a83 100644
--- a/vmm/src/memory_manager.rs
+++ b/vmm/src/memory_manager.rs
@@ -25,9 +25,7 @@ use devices::ioapic;
 #[cfg(target_arch = "aarch64")]
 use hypervisor::HypervisorVmError;
 use libc::_SC_NPROCESSORS_ONLN;
-#[cfg(all(target_arch = "x86_64", feature = "guest_debug"))]
-use log::debug;
-use log::{error, info, warn};
+use log::{debug, error, info, warn};
 use serde::{Deserialize, Serialize};
 use thiserror::Error;
 use tracer::trace_scoped;
@@ -1490,17 +1488,20 @@ impl MemoryManager {
             });
         }
 
-        if region.file_offset().is_none() && thp {
-            info!(
-                "Anonymous mapping at 0x{:x} (size = 0x{:x})",
-                region.as_ptr() as u64,
-                size
-            );
+        info!(
+            "RAM region mapping at 0x{:x} (size = 0x{:x})",
+            region.as_ptr() as u64,
+            size
+        );
+
+        if thp && !hugepages {
             // SAFETY: FFI call with correct arguments
             let ret = unsafe { libc::madvise(region.as_ptr() as _, size, libc::MADV_HUGEPAGE) };
             if ret != 0 {
                 let e = io::Error::last_os_error();
                 warn!("Failed to mark pages as THP eligible: {e}");
+            } else {
+                debug!("Successfully marked pages as THP eligible");
             }
         }