From c1452a02c5420fab4934ab273247c922f723889a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Lesimple?= <speed47_github@speed47.net>
Date: Mon, 6 Apr 2026 12:58:03 +0200
Subject: [PATCH] fix: CPUs affected by MSBDS but not MDS (fix #351)

---
 src/libs/200_cpu_affected.sh |  5 +++++
 src/libs/210_cpu_detect.sh   | 31 +++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/src/libs/200_cpu_affected.sh b/src/libs/200_cpu_affected.sh
index 39e662d..b41e5df 100644
--- a/src/libs/200_cpu_affected.sh
+++ b/src/libs/200_cpu_affected.sh
@@ -124,6 +124,11 @@ is_cpu_affected() {
         _infer_immune mlpds
         _infer_immune mdsum
         pr_debug "is_cpu_affected: cpu not affected by Microarchitectural Data Sampling"
+    elif is_cpu_msbds_only; then
+        _infer_immune mfbds
+        _infer_immune mlpds
+        _infer_immune mdsum
+        pr_debug "is_cpu_affected: cpu only affected by MSBDS, not MFBDS/MLPDS/MDSUM"
     fi
 
     if is_cpu_taa_free; then
diff --git a/src/libs/210_cpu_detect.sh b/src/libs/210_cpu_detect.sh
index dce3c3d..41f24e4 100644
--- a/src/libs/210_cpu_detect.sh
+++ b/src/libs/210_cpu_detect.sh
@@ -85,6 +85,37 @@ is_cpu_mds_free() {
     return 1
 }
 
+# Check whether the CPU is known to be affected by MSBDS only (not MFBDS/MLPDS/MDSUM)
+# These CPUs have a different microarchitecture that is only susceptible to
+# Microarchitectural Store Buffer Data Sampling, not the other MDS variants.
+# Returns: 0 if MSBDS-only, 1 otherwise
+is_cpu_msbds_only() {
+    # source: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/kernel/cpu/common.c
+    #VULNWL_INTEL(ATOM_SILVERMONT,       MSBDS_ONLY),
+    #VULNWL_INTEL(ATOM_SILVERMONT_D,     MSBDS_ONLY),
+    #VULNWL_INTEL(ATOM_SILVERMONT_MID,   MSBDS_ONLY),
+    #VULNWL_INTEL(ATOM_SILVERMONT_MID2,  MSBDS_ONLY),
+    #VULNWL_INTEL(ATOM_AIRMONT,          MSBDS_ONLY),
+    #VULNWL_INTEL(XEON_PHI_KNL,         MSBDS_ONLY),
+    #VULNWL_INTEL(XEON_PHI_KNM,         MSBDS_ONLY),
+    parse_cpu_details
+    if is_intel; then
+        if [ "$cpu_family" = 6 ]; then
+            if [ "$cpu_model" = "$INTEL_FAM6_ATOM_SILVERMONT" ] ||
+                [ "$cpu_model" = "$INTEL_FAM6_ATOM_SILVERMONT_D" ] ||
+                [ "$cpu_model" = "$INTEL_FAM6_ATOM_SILVERMONT_MID" ] ||
+                [ "$cpu_model" = "$INTEL_FAM6_ATOM_SILVERMONT_MID2" ] ||
+                [ "$cpu_model" = "$INTEL_FAM6_ATOM_AIRMONT" ] ||
+                [ "$cpu_model" = "$INTEL_FAM6_XEON_PHI_KNL" ] ||
+                [ "$cpu_model" = "$INTEL_FAM6_XEON_PHI_KNM" ]; then
+                return 0
+            fi
+        fi
+    fi
+
+    return 1
+}
+
 # Check whether the CPU is known to be unaffected by TSX Asynchronous Abort (TAA)
 # Returns: 0 if TAA-free, 1 if affected or unknown
 is_cpu_taa_free() {