From 031201dc6adb4bff784140768e549c8bd6c9096e Mon Sep 17 00:00:00 2001
From: Andrea Bolognani <abologna@redhat.com>
Date: Sun, 11 Jan 2026 20:35:10 +0100
Subject: [PATCH] msr_module_load
---
 libvirt.spec.in                        | 18 ++++++++++++++++++
 meson.build                            | 14 ++++++++++++++
 meson_options.txt                      |  1 +
 src/util/libvirt-msr.modules-load.conf |  1 +
 src/util/meson.build                   |  8 ++++++++
 tools/virt-host-validate-qemu.c        |  7 +++++++
 6 files changed, 49 insertions(+)
 create mode 100644 src/util/libvirt-msr.modules-load.conf

diff --git a/libvirt.spec.in b/libvirt.spec.in
index ccfe75135b..305ddc0e5f 100644
--- a/libvirt.spec.in
+++ b/libvirt.spec.in
@@ -211,6 +211,13 @@
     %define with_dmidecode 0%{!?_without_dmidecode:1}
 %endif
 
+%define with_msr_module_load 0
+%if 0%{?fedora} || 0%{?rhel}
+  %ifarch %{arches_x86}
+    %define with_msr_module_load 0%{!?_without_msr_module_load:1}
+  %endif
+%endif
+
 %define with_modular_daemons 0
 %if 0%{?fedora} || 0%{?rhel}
     %define with_modular_daemons 1
@@ -1338,6 +1345,12 @@ exit 1
     %define arg_remote_mode -Dremote_default_mode=legacy
 %endif
 
+%if %{with_msr_module_load}
+    %define arg_msr_module_load -Dmsr_module_load=enabled
+%else
+    %define arg_msr_module_load -Dmsr_module_load=disabled
+%endif
+
 %define when  %(date +"%%F-%%T")
 %define where %(hostname)
 %define who   %{?packager}%{!?packager:Unknown}
@@ -1422,6 +1435,7 @@ export SOURCE_DATE_EPOCH=$(stat --printf='%Y' %{_specdir}/libvirt.spec)
            -Dtls_priority=%{tls_priority} \
            -Dsysctl_config=enabled \
            -Dssh_proxy=enabled \
+           %{?arg_msr_module_load} \
            %{?enable_werror} \
            -Dexpensive_tests=enabled \
            -Dinit_script=systemd \
@@ -1509,6 +1523,7 @@ export SOURCE_DATE_EPOCH=$(stat --printf='%Y' %{_specdir}/libvirt.spec)
   -Dstorage_zfs=disabled \
   -Dsysctl_config=disabled \
   -Dssh_proxy=disabled \
+  -Dmsr_module_load=disabled \
   -Dtests=disabled \
   -Dudev=disabled \
   -Dwireshark_dissector=disabled \
@@ -2512,6 +2527,9 @@ exit 0
     %endif
 %dir %{_datadir}/libvirt/cpu_map
 %{_datadir}/libvirt/cpu_map/*.xml
+    %if %{with_msr_module_load}
+%{_sysconfdir}/modules-load.d/libvirt-msr.conf
+    %endif
 
     %if %{with_wireshark}
 %files wireshark
diff --git a/meson.build b/meson.build
index 2f807bc3a2..7bcdb35512 100644
--- a/meson.build
+++ b/meson.build
@@ -2042,6 +2042,19 @@ if prio == 'auto'
 endif
 conf.set_quoted('TLS_PRIORITY', prio)
 
+if not get_option('msr_module_load').disabled()
+  if host_machine.system() != 'linux'
+    if get_option('msr_module_load').enabled()
+      error('msr module loading can be enabled on Linux only')
+    endif
+  endif
+  if host_machine.cpu_family() not in [ 'x86', 'x86_64' ]
+    if get_option('msr_module_load').enabled()
+      error('msr module loading can be enabled on x86 only')
+    endif
+  endif
+  conf.set('WITH_MSR_MODULE_LOAD', 1)
+endif
 
 # test options
 
@@ -2337,6 +2350,7 @@ misc_summary = {
   'pm_utils': conf.has('WITH_PM_UTILS'),
   'SSH proxy': conf.has('WITH_SSH_PROXY'),
   'sysctl config': conf.has('WITH_SYSCTL'),
+  'msr module load': conf.has('WITH_MSR_MODULE_LOAD'),
   'tests': tests_enabled,
   'TLS priority': conf.get_unquoted('TLS_PRIORITY'),
   'virt-host-validate': conf.has('WITH_HOST_VALIDATE'),
diff --git a/meson_options.txt b/meson_options.txt
index e12ace4e11..4b6c030e92 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -133,3 +133,4 @@ option('pm_utils', type: 'feature', value: 'auto', description: 'use pm-utils fo
 option('ssh_proxy', type: 'feature', value: 'auto', description: 'Build ssh-proxy for ssh over vsock')
 option('sysctl_config', type: 'feature', value: 'auto', description: 'Whether to install sysctl configs')
 option('tls_priority', type: 'string', value: 'auto', description: 'set the default TLS session priority string')
+option('msr_module_load', type: 'feature', value: 'auto', description: 'Install modules-load.d file for msr module')
diff --git a/src/util/libvirt-msr.modules-load.conf b/src/util/libvirt-msr.modules-load.conf
new file mode 100644
index 0000000000..3e5ee7fa15
--- /dev/null
+++ b/src/util/libvirt-msr.modules-load.conf
@@ -0,0 +1 @@
+msr
diff --git a/src/util/meson.build b/src/util/meson.build
index 4950a795cc..3d2dbe199d 100644
--- a/src/util/meson.build
+++ b/src/util/meson.build
@@ -223,4 +223,12 @@ if conf.has('WITH_LIBVIRTD')
   }
 endif
 
+if conf.has('WITH_MSR_MODULE_LOAD')
+  install_data(
+    'libvirt-msr.modules-load.conf',
+    install_dir: sysconfdir / 'modules-load.d',
+    rename: 'libvirt-msr.conf',
+  )
+endif
+
 util_inc_dir = include_directories('.')
diff --git a/tools/virt-host-validate-qemu.c b/tools/virt-host-validate-qemu.c
index c5c1a0ab7e..68e5d037c8 100644
--- a/tools/virt-host-validate-qemu.c
+++ b/tools/virt-host-validate-qemu.c
@@ -104,6 +104,13 @@ int virHostValidateQEMU(void)
             virValidatePass();
     }
 
+    if (ARCH_IS_X86(arch)) {
+        if (virHostValidateDeviceExists("QEMU", "/dev/cpu/0/msr",
+                                        VIR_VALIDATE_WARN,
+                                        _("Load the 'msr' module for better x86 CPU features detection")) < 0)
+            ret = -1;
+    }
+
     if (virHostValidateDeviceExists("QEMU", "/dev/vhost-net",
                                     VIR_VALIDATE_WARN,
                                     _("Load the 'vhost_net' module to improve performance of virtio networking")) < 0)
-- 
2.52.0